[rust-lightning] / lightning / src / ln / chan_utils.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! Various utilities for building scripts and deriving keys related to channels. These are
//! largely of interest for those implementing chain::keysinterface::Sign message signing by hand.

use bitcoin::blockdata::script::{Script,Builder};
use bitcoin::blockdata::opcodes;
use bitcoin::blockdata::transaction::{TxIn,TxOut,OutPoint,Transaction, EcdsaSighashType};
use bitcoin::util::sighash;

use bitcoin::hashes::{Hash, HashEngine};
use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::ripemd160::Hash as Ripemd160;
use bitcoin::hash_types::{Txid, PubkeyHash};

use ln::{PaymentHash, PaymentPreimage};
use ln::msgs::DecodeError;
use util::ser::{Readable, Writeable, Writer};
use util::{byte_utils, transaction_utils};

use bitcoin::hash_types::WPubkeyHash;
use bitcoin::secp256k1::{SecretKey, PublicKey, Scalar};
use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature, Message};
use bitcoin::secp256k1::Error as SecpError;
use bitcoin::{PackedLockTime, secp256k1, Sequence, Witness};

use io;
use prelude::*;
use core::cmp;
use ln::chan_utils;
use util::transaction_utils::sort_outputs;
use ln::channel::{INITIAL_COMMITMENT_NUMBER, ANCHOR_OUTPUT_VALUE_SATOSHI};
use core::ops::Deref;
use chain;
use util::crypto::sign;

pub(crate) const MAX_HTLCS: u16 = 483;

/// Gets the weight for an HTLC-Success transaction.
#[inline]
pub fn htlc_success_tx_weight(opt_anchors: bool) -> u64 {
        const HTLC_SUCCESS_TX_WEIGHT: u64 = 703;
        const HTLC_SUCCESS_ANCHOR_TX_WEIGHT: u64 = 706;
        if opt_anchors { HTLC_SUCCESS_ANCHOR_TX_WEIGHT } else { HTLC_SUCCESS_TX_WEIGHT }
}

/// Gets the weight for an HTLC-Timeout transaction.
#[inline]
pub fn htlc_timeout_tx_weight(opt_anchors: bool) -> u64 {
        const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663;
        const HTLC_TIMEOUT_ANCHOR_TX_WEIGHT: u64 = 666;
        if opt_anchors { HTLC_TIMEOUT_ANCHOR_TX_WEIGHT } else { HTLC_TIMEOUT_TX_WEIGHT }
}

#[derive(PartialEq)]
pub(crate) enum HTLCType {
        AcceptedHTLC,
        OfferedHTLC
}

impl HTLCType {
        /// Check if a given tx witnessScript len matchs one of a pre-signed HTLC
        pub(crate) fn scriptlen_to_htlctype(witness_script_len: usize) ->  Option<HTLCType> {
                if witness_script_len == 133 {
                        Some(HTLCType::OfferedHTLC)
                } else if witness_script_len >= 136 && witness_script_len <= 139 {
                        Some(HTLCType::AcceptedHTLC)
                } else {
                        None
                }
        }
}

// Various functions for key derivation and transaction creation for use within channels. Primarily
// used in Channel and ChannelMonitor.

/// Build the commitment secret from the seed and the commitment number
pub fn build_commitment_secret(commitment_seed: &[u8; 32], idx: u64) -> [u8; 32] {
        let mut res: [u8; 32] = commitment_seed.clone();
        for i in 0..48 {
                let bitpos = 47 - i;
                if idx & (1 << bitpos) == (1 << bitpos) {
                        res[bitpos / 8] ^= 1 << (bitpos & 7);
                        res = Sha256::hash(&res).into_inner();
                }
        }
        res
}

/// Build a closing transaction
pub fn build_closing_transaction(to_holder_value_sat: u64, to_counterparty_value_sat: u64, to_holder_script: Script, to_counterparty_script: Script, funding_outpoint: OutPoint) -> Transaction {
        let txins = {
                let mut ins: Vec<TxIn> = Vec::new();
                ins.push(TxIn {
                        previous_output: funding_outpoint,
                        script_sig: Script::new(),
                        sequence: Sequence::MAX,
                        witness: Witness::new(),
                });
                ins
        };

        let mut txouts: Vec<(TxOut, ())> = Vec::new();

        if to_counterparty_value_sat > 0 {
                txouts.push((TxOut {
                        script_pubkey: to_counterparty_script,
                        value: to_counterparty_value_sat
                }, ()));
        }

        if to_holder_value_sat > 0 {
                txouts.push((TxOut {
                        script_pubkey: to_holder_script,
                        value: to_holder_value_sat
                }, ()));
        }

        transaction_utils::sort_outputs(&mut txouts, |_, _| { cmp::Ordering::Equal }); // Ordering doesnt matter if they used our pubkey...

        let mut outputs: Vec<TxOut> = Vec::new();
        for out in txouts.drain(..) {
                outputs.push(out.0);
        }

        Transaction {
                version: 2,
                lock_time: PackedLockTime::ZERO,
                input: txins,
                output: outputs,
        }
}

/// Implements the per-commitment secret storage scheme from
/// [BOLT 3](https://github.com/lightning/bolts/blob/dcbf8583976df087c79c3ce0b535311212e6812d/03-transactions.md#efficient-per-commitment-secret-storage).
///
/// Allows us to keep track of all of the revocation secrets of our counterparty in just 50*32 bytes
/// or so.
#[derive(Clone)]
pub struct CounterpartyCommitmentSecrets {
        old_secrets: [([u8; 32], u64); 49],
}

impl PartialEq for CounterpartyCommitmentSecrets {
        fn eq(&self, other: &Self) -> bool {
                for (&(ref secret, ref idx), &(ref o_secret, ref o_idx)) in self.old_secrets.iter().zip(other.old_secrets.iter()) {
                        if secret != o_secret || idx != o_idx {
                                return false
                        }
                }
                true
        }
}

impl CounterpartyCommitmentSecrets {
        /// Creates a new empty `CounterpartyCommitmentSecrets` structure.
        pub fn new() -> Self {
                Self { old_secrets: [([0; 32], 1 << 48); 49], }
        }

        #[inline]
        fn place_secret(idx: u64) -> u8 {
                for i in 0..48 {
                        if idx & (1 << i) == (1 << i) {
                                return i
                        }
                }
                48
        }

        /// Returns the minimum index of all stored secrets. Note that indexes start
        /// at 1 << 48 and get decremented by one for each new secret.
        pub fn get_min_seen_secret(&self) -> u64 {
                //TODO This can be optimized?
                let mut min = 1 << 48;
                for &(_, idx) in self.old_secrets.iter() {
                        if idx < min {
                                min = idx;
                        }
                }
                min
        }

        #[inline]
        fn derive_secret(secret: [u8; 32], bits: u8, idx: u64) -> [u8; 32] {
                let mut res: [u8; 32] = secret;
                for i in 0..bits {
                        let bitpos = bits - 1 - i;
                        if idx & (1 << bitpos) == (1 << bitpos) {
                                res[(bitpos / 8) as usize] ^= 1 << (bitpos & 7);
                                res = Sha256::hash(&res).into_inner();
                        }
                }
                res
        }

        /// Inserts the `secret` at `idx`. Returns `Ok(())` if the secret
        /// was generated in accordance with BOLT 3 and is consistent with previous secrets.
        pub fn provide_secret(&mut self, idx: u64, secret: [u8; 32]) -> Result<(), ()> {
                let pos = Self::place_secret(idx);
                for i in 0..pos {
                        let (old_secret, old_idx) = self.old_secrets[i as usize];
                        if Self::derive_secret(secret, pos, old_idx) != old_secret {
                                return Err(());
                        }
                }
                if self.get_min_seen_secret() <= idx {
                        return Ok(());
                }
                self.old_secrets[pos as usize] = (secret, idx);
                Ok(())
        }

        /// Returns the secret at `idx`.
        /// Returns `None` if `idx` is < [`CounterpartyCommitmentSecrets::get_min_seen_secret`].
        pub fn get_secret(&self, idx: u64) -> Option<[u8; 32]> {
                for i in 0..self.old_secrets.len() {
                        if (idx & (!((1 << i) - 1))) == self.old_secrets[i].1 {
                                return Some(Self::derive_secret(self.old_secrets[i].0, i as u8, idx))
                        }
                }
                assert!(idx < self.get_min_seen_secret());
                None
        }
}

impl Writeable for CounterpartyCommitmentSecrets {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                for &(ref secret, ref idx) in self.old_secrets.iter() {
                        writer.write_all(secret)?;
                        writer.write_all(&byte_utils::be64_to_array(*idx))?;
                }
                write_tlv_fields!(writer, {});
                Ok(())
        }
}
impl Readable for CounterpartyCommitmentSecrets {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                let mut old_secrets = [([0; 32], 1 << 48); 49];
                for &mut (ref mut secret, ref mut idx) in old_secrets.iter_mut() {
                        *secret = Readable::read(reader)?;
                        *idx = Readable::read(reader)?;
                }
                read_tlv_fields!(reader, {});
                Ok(Self { old_secrets })
        }
}

/// Derives a per-commitment-transaction private key (eg an htlc key or delayed_payment key)
/// from the base secret and the per_commitment_point.
///
/// Note that this is infallible iff we trust that at least one of the two input keys are randomly
/// generated (ie our own).
pub fn derive_private_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result<SecretKey, SecpError> {
        let mut sha = Sha256::engine();
        sha.input(&per_commitment_point.serialize());
        sha.input(&PublicKey::from_secret_key(&secp_ctx, &base_secret).serialize());
        let res = Sha256::from_engine(sha).into_inner();

        base_secret.clone().add_tweak(&Scalar::from_be_bytes(res).unwrap())
}

/// Derives a per-commitment-transaction public key (eg an htlc key or a delayed_payment key)
/// from the base point and the per_commitment_key. This is the public equivalent of
/// derive_private_key - using only public keys to derive a public key instead of private keys.
///
/// Note that this is infallible iff we trust that at least one of the two input keys are randomly
/// generated (ie our own).
pub fn derive_public_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result<PublicKey, SecpError> {
        let mut sha = Sha256::engine();
        sha.input(&per_commitment_point.serialize());
        sha.input(&base_point.serialize());
        let res = Sha256::from_engine(sha).into_inner();

        let hashkey = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&res)?);
        base_point.combine(&hashkey)
}

/// Derives a per-commitment-transaction revocation key from its constituent parts.
///
/// Only the cheating participant owns a valid witness to propagate a revoked 
/// commitment transaction, thus per_commitment_secret always come from cheater
/// and revocation_base_secret always come from punisher, which is the broadcaster
/// of the transaction spending with this key knowledge.
///
/// Note that this is infallible iff we trust that at least one of the two input keys are randomly
/// generated (ie our own).
pub fn derive_private_revocation_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_secret: &SecretKey, countersignatory_revocation_base_secret: &SecretKey) -> Result<SecretKey, SecpError> {
        let countersignatory_revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &countersignatory_revocation_base_secret);
        let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);

        let rev_append_commit_hash_key = {
                let mut sha = Sha256::engine();
                sha.input(&countersignatory_revocation_base_point.serialize());
                sha.input(&per_commitment_point.serialize());

                Sha256::from_engine(sha).into_inner()
        };
        let commit_append_rev_hash_key = {
                let mut sha = Sha256::engine();
                sha.input(&per_commitment_point.serialize());
                sha.input(&countersignatory_revocation_base_point.serialize());

                Sha256::from_engine(sha).into_inner()
        };

        let countersignatory_contrib = countersignatory_revocation_base_secret.clone().mul_tweak(&Scalar::from_be_bytes(rev_append_commit_hash_key).unwrap())?;
        let broadcaster_contrib = per_commitment_secret.clone().mul_tweak(&Scalar::from_be_bytes(commit_append_rev_hash_key).unwrap())?;
        countersignatory_contrib.add_tweak(&Scalar::from_be_bytes(broadcaster_contrib.secret_bytes()).unwrap())
}

/// Derives a per-commitment-transaction revocation public key from its constituent parts. This is
/// the public equivalend of derive_private_revocation_key - using only public keys to derive a
/// public key instead of private keys.
///
/// Only the cheating participant owns a valid witness to propagate a revoked 
/// commitment transaction, thus per_commitment_point always come from cheater
/// and revocation_base_point always come from punisher, which is the broadcaster
/// of the transaction spending with this key knowledge.
///
/// Note that this is infallible iff we trust that at least one of the two input keys are randomly
/// generated (ie our own).
pub fn derive_public_revocation_key<T: secp256k1::Verification>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, countersignatory_revocation_base_point: &PublicKey) -> Result<PublicKey, SecpError> {
        let rev_append_commit_hash_key = {
                let mut sha = Sha256::engine();
                sha.input(&countersignatory_revocation_base_point.serialize());
                sha.input(&per_commitment_point.serialize());

                Sha256::from_engine(sha).into_inner()
        };
        let commit_append_rev_hash_key = {
                let mut sha = Sha256::engine();
                sha.input(&per_commitment_point.serialize());
                sha.input(&countersignatory_revocation_base_point.serialize());

                Sha256::from_engine(sha).into_inner()
        };

        let countersignatory_contrib = countersignatory_revocation_base_point.clone().mul_tweak(&secp_ctx, &Scalar::from_be_bytes(rev_append_commit_hash_key).unwrap())?;
        let broadcaster_contrib = per_commitment_point.clone().mul_tweak(&secp_ctx, &Scalar::from_be_bytes(commit_append_rev_hash_key).unwrap())?;
        countersignatory_contrib.combine(&broadcaster_contrib)
}

/// The set of public keys which are used in the creation of one commitment transaction.
/// These are derived from the channel base keys and per-commitment data.
///
/// A broadcaster key is provided from potential broadcaster of the computed transaction.
/// A countersignatory key is coming from a protocol participant unable to broadcast the
/// transaction.
///
/// These keys are assumed to be good, either because the code derived them from
/// channel basepoints via the new function, or they were obtained via
/// CommitmentTransaction.trust().keys() because we trusted the source of the
/// pre-calculated keys.
#[derive(PartialEq, Clone)]
pub struct TxCreationKeys {
        /// The broadcaster's per-commitment public key which was used to derive the other keys.
        pub per_commitment_point: PublicKey,
        /// The revocation key which is used to allow the broadcaster of the commitment
        /// transaction to provide their counterparty the ability to punish them if they broadcast
        /// an old state.
        pub revocation_key: PublicKey,
        /// Broadcaster's HTLC Key
        pub broadcaster_htlc_key: PublicKey,
        /// Countersignatory's HTLC Key
        pub countersignatory_htlc_key: PublicKey,
        /// Broadcaster's Payment Key (which isn't allowed to be spent from for some delay)
        pub broadcaster_delayed_payment_key: PublicKey,
}

impl_writeable_tlv_based!(TxCreationKeys, {
        (0, per_commitment_point, required),
        (2, revocation_key, required),
        (4, broadcaster_htlc_key, required),
        (6, countersignatory_htlc_key, required),
        (8, broadcaster_delayed_payment_key, required),
});

/// One counterparty's public keys which do not change over the life of a channel.
#[derive(Clone, PartialEq)]
pub struct ChannelPublicKeys {
        /// The public key which is used to sign all commitment transactions, as it appears in the
        /// on-chain channel lock-in 2-of-2 multisig output.
        pub funding_pubkey: PublicKey,
        /// The base point which is used (with derive_public_revocation_key) to derive per-commitment
        /// revocation keys. This is combined with the per-commitment-secret generated by the
        /// counterparty to create a secret which the counterparty can reveal to revoke previous
        /// states.
        pub revocation_basepoint: PublicKey,
        /// The public key on which the non-broadcaster (ie the countersignatory) receives an immediately
        /// spendable primary channel balance on the broadcaster's commitment transaction. This key is
        /// static across every commitment transaction.
        pub payment_point: PublicKey,
        /// The base point which is used (with derive_public_key) to derive a per-commitment payment
        /// public key which receives non-HTLC-encumbered funds which are only available for spending
        /// after some delay (or can be claimed via the revocation path).
        pub delayed_payment_basepoint: PublicKey,
        /// The base point which is used (with derive_public_key) to derive a per-commitment public key
        /// which is used to encumber HTLC-in-flight outputs.
        pub htlc_basepoint: PublicKey,
}

impl_writeable_tlv_based!(ChannelPublicKeys, {
        (0, funding_pubkey, required),
        (2, revocation_basepoint, required),
        (4, payment_point, required),
        (6, delayed_payment_basepoint, required),
        (8, htlc_basepoint, required),
});

impl TxCreationKeys {
        /// Create per-state keys from channel base points and the per-commitment point.
        /// Key set is asymmetric and can't be used as part of counter-signatory set of transactions.
        pub fn derive_new<T: secp256k1::Signing + secp256k1::Verification>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, broadcaster_delayed_payment_base: &PublicKey, broadcaster_htlc_base: &PublicKey, countersignatory_revocation_base: &PublicKey, countersignatory_htlc_base: &PublicKey) -> Result<TxCreationKeys, SecpError> {
                Ok(TxCreationKeys {
                        per_commitment_point: per_commitment_point.clone(),
                        revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &countersignatory_revocation_base)?,
                        broadcaster_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &broadcaster_htlc_base)?,
                        countersignatory_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &countersignatory_htlc_base)?,
                        broadcaster_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &broadcaster_delayed_payment_base)?,
                })
        }

        /// Generate per-state keys from channel static keys.
        /// Key set is asymmetric and can't be used as part of counter-signatory set of transactions.
        pub fn from_channel_static_keys<T: secp256k1::Signing + secp256k1::Verification>(per_commitment_point: &PublicKey, broadcaster_keys: &ChannelPublicKeys, countersignatory_keys: &ChannelPublicKeys, secp_ctx: &Secp256k1<T>) -> Result<TxCreationKeys, SecpError> {
                TxCreationKeys::derive_new(
                        &secp_ctx,
                        &per_commitment_point,
                        &broadcaster_keys.delayed_payment_basepoint,
                        &broadcaster_keys.htlc_basepoint,
                        &countersignatory_keys.revocation_basepoint,
                        &countersignatory_keys.htlc_basepoint,
                )
        }
}

/// The maximum length of a script returned by get_revokeable_redeemscript.
// Calculated as 6 bytes of opcodes, 1 byte push plus 2 bytes for contest_delay, and two public
// keys of 33 bytes (+ 1 push).
pub const REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH: usize = 6 + 3 + 34*2;

/// A script either spendable by the revocation
/// key or the broadcaster_delayed_payment_key and satisfying the relative-locktime OP_CSV constrain.
/// Encumbering a `to_holder` output on a commitment transaction or 2nd-stage HTLC transactions.
pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, contest_delay: u16, broadcaster_delayed_payment_key: &PublicKey) -> Script {
        let res = Builder::new().push_opcode(opcodes::all::OP_IF)
                      .push_slice(&revocation_key.serialize())
                      .push_opcode(opcodes::all::OP_ELSE)
                      .push_int(contest_delay as i64)
                      .push_opcode(opcodes::all::OP_CSV)
                      .push_opcode(opcodes::all::OP_DROP)
                      .push_slice(&broadcaster_delayed_payment_key.serialize())
                      .push_opcode(opcodes::all::OP_ENDIF)
                      .push_opcode(opcodes::all::OP_CHECKSIG)
                      .into_script();
        debug_assert!(res.len() <= REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH);
        res
}

#[derive(Clone, PartialEq)]
/// Information about an HTLC as it appears in a commitment transaction
pub struct HTLCOutputInCommitment {
        /// Whether the HTLC was "offered" (ie outbound in relation to this commitment transaction).
        /// Note that this is not the same as whether it is ountbound *from us*. To determine that you
        /// need to compare this value to whether the commitment transaction in question is that of
        /// the counterparty or our own.
        pub offered: bool,
        /// The value, in msat, of the HTLC. The value as it appears in the commitment transaction is
        /// this divided by 1000.
        pub amount_msat: u64,
        /// The CLTV lock-time at which this HTLC expires.
        pub cltv_expiry: u32,
        /// The hash of the preimage which unlocks this HTLC.
        pub payment_hash: PaymentHash,
        /// The position within the commitment transactions' outputs. This may be None if the value is
        /// below the dust limit (in which case no output appears in the commitment transaction and the
        /// value is spent to additional transaction fees).
        pub transaction_output_index: Option<u32>,
}

impl_writeable_tlv_based!(HTLCOutputInCommitment, {
        (0, offered, required),
        (2, amount_msat, required),
        (4, cltv_expiry, required),
        (6, payment_hash, required),
        (8, transaction_output_index, option),
});

#[inline]
pub(crate) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, opt_anchors: bool, broadcaster_htlc_key: &PublicKey, countersignatory_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script {
        let payment_hash160 = Ripemd160::hash(&htlc.payment_hash.0[..]).into_inner();
        if htlc.offered {
                let mut bldr = Builder::new().push_opcode(opcodes::all::OP_DUP)
                              .push_opcode(opcodes::all::OP_HASH160)
                              .push_slice(&PubkeyHash::hash(&revocation_key.serialize())[..])
                              .push_opcode(opcodes::all::OP_EQUAL)
                              .push_opcode(opcodes::all::OP_IF)
                              .push_opcode(opcodes::all::OP_CHECKSIG)
                              .push_opcode(opcodes::all::OP_ELSE)
                              .push_slice(&countersignatory_htlc_key.serialize()[..])
                              .push_opcode(opcodes::all::OP_SWAP)
                              .push_opcode(opcodes::all::OP_SIZE)
                              .push_int(32)
                              .push_opcode(opcodes::all::OP_EQUAL)
                              .push_opcode(opcodes::all::OP_NOTIF)
                              .push_opcode(opcodes::all::OP_DROP)
                              .push_int(2)
                              .push_opcode(opcodes::all::OP_SWAP)
                              .push_slice(&broadcaster_htlc_key.serialize()[..])
                              .push_int(2)
                              .push_opcode(opcodes::all::OP_CHECKMULTISIG)
                              .push_opcode(opcodes::all::OP_ELSE)
                              .push_opcode(opcodes::all::OP_HASH160)
                              .push_slice(&payment_hash160)
                              .push_opcode(opcodes::all::OP_EQUALVERIFY)
                              .push_opcode(opcodes::all::OP_CHECKSIG)
                              .push_opcode(opcodes::all::OP_ENDIF);
                if opt_anchors {
                        bldr = bldr.push_opcode(opcodes::all::OP_PUSHNUM_1)
                                .push_opcode(opcodes::all::OP_CSV)
                                .push_opcode(opcodes::all::OP_DROP);
                }
                bldr.push_opcode(opcodes::all::OP_ENDIF)
                        .into_script()
        } else {
                        let mut bldr = Builder::new().push_opcode(opcodes::all::OP_DUP)
                              .push_opcode(opcodes::all::OP_HASH160)
                              .push_slice(&PubkeyHash::hash(&revocation_key.serialize())[..])
                              .push_opcode(opcodes::all::OP_EQUAL)
                              .push_opcode(opcodes::all::OP_IF)
                              .push_opcode(opcodes::all::OP_CHECKSIG)
                              .push_opcode(opcodes::all::OP_ELSE)
                              .push_slice(&countersignatory_htlc_key.serialize()[..])
                              .push_opcode(opcodes::all::OP_SWAP)
                              .push_opcode(opcodes::all::OP_SIZE)
                              .push_int(32)
                              .push_opcode(opcodes::all::OP_EQUAL)
                              .push_opcode(opcodes::all::OP_IF)
                              .push_opcode(opcodes::all::OP_HASH160)
                              .push_slice(&payment_hash160)
                              .push_opcode(opcodes::all::OP_EQUALVERIFY)
                              .push_int(2)
                              .push_opcode(opcodes::all::OP_SWAP)
                              .push_slice(&broadcaster_htlc_key.serialize()[..])
                              .push_int(2)
                              .push_opcode(opcodes::all::OP_CHECKMULTISIG)
                              .push_opcode(opcodes::all::OP_ELSE)
                              .push_opcode(opcodes::all::OP_DROP)
                              .push_int(htlc.cltv_expiry as i64)
                              .push_opcode(opcodes::all::OP_CLTV)
                              .push_opcode(opcodes::all::OP_DROP)
                              .push_opcode(opcodes::all::OP_CHECKSIG)
                              .push_opcode(opcodes::all::OP_ENDIF);
                if opt_anchors {
                        bldr = bldr.push_opcode(opcodes::all::OP_PUSHNUM_1)
                                .push_opcode(opcodes::all::OP_CSV)
                                .push_opcode(opcodes::all::OP_DROP);
                }
                bldr.push_opcode(opcodes::all::OP_ENDIF)
                        .into_script()
        }
}

/// Gets the witness redeemscript for an HTLC output in a commitment transaction. Note that htlc
/// does not need to have its previous_output_index filled.
#[inline]
pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, opt_anchors: bool, keys: &TxCreationKeys) -> Script {
        get_htlc_redeemscript_with_explicit_keys(htlc, opt_anchors, &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key)
}

/// Gets the redeemscript for a funding output from the two funding public keys.
/// Note that the order of funding public keys does not matter.
pub fn make_funding_redeemscript(broadcaster: &PublicKey, countersignatory: &PublicKey) -> Script {
        let broadcaster_funding_key = broadcaster.serialize();
        let countersignatory_funding_key = countersignatory.serialize();

        let builder = Builder::new().push_opcode(opcodes::all::OP_PUSHNUM_2);
        if broadcaster_funding_key[..] < countersignatory_funding_key[..] {
                builder.push_slice(&broadcaster_funding_key)
                        .push_slice(&countersignatory_funding_key)
        } else {
                builder.push_slice(&countersignatory_funding_key)
                        .push_slice(&broadcaster_funding_key)
        }.push_opcode(opcodes::all::OP_PUSHNUM_2).push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script()
}

/// Builds an unsigned HTLC-Success or HTLC-Timeout transaction from the given channel and HTLC
/// parameters. This is used by [`TrustedCommitmentTransaction::get_htlc_sigs`] to fetch the
/// transaction which needs signing, and can be used to construct an HTLC transaction which is
/// broadcastable given a counterparty HTLC signature.
///
/// Panics if htlc.transaction_output_index.is_none() (as such HTLCs do not appear in the
/// commitment transaction).
pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, opt_anchors: bool, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
        let mut txins: Vec<TxIn> = Vec::new();
        txins.push(TxIn {
                previous_output: OutPoint {
                        txid: commitment_txid.clone(),
                        vout: htlc.transaction_output_index.expect("Can't build an HTLC transaction for a dust output"),
                },
                script_sig: Script::new(),
                sequence: Sequence(if opt_anchors { 1 } else { 0 }),
                witness: Witness::new(),
        });

        let weight = if htlc.offered {
                htlc_timeout_tx_weight(opt_anchors)
        } else {
                htlc_success_tx_weight(opt_anchors)
        };
        let output_value = if opt_anchors {
                htlc.amount_msat / 1000
        } else {
                let total_fee = feerate_per_kw as u64 * weight / 1000;
                htlc.amount_msat / 1000 - total_fee
        };

        let mut txouts: Vec<TxOut> = Vec::new();
        txouts.push(TxOut {
                script_pubkey: get_revokeable_redeemscript(revocation_key, contest_delay, broadcaster_delayed_payment_key).to_v0_p2wsh(),
                value: output_value,
        });

        Transaction {
                version: 2,
                lock_time: PackedLockTime(if htlc.offered { htlc.cltv_expiry } else { 0 }),
                input: txins,
                output: txouts,
        }
}

/// Gets the witnessScript for the to_remote output when anchors are enabled.
#[inline]
pub(crate) fn get_to_countersignatory_with_anchors_redeemscript(payment_point: &PublicKey) -> Script {
        Builder::new()
                .push_slice(&payment_point.serialize()[..])
                .push_opcode(opcodes::all::OP_CHECKSIGVERIFY)
                .push_int(1)
                .push_opcode(opcodes::all::OP_CSV)
                .into_script()
}

/// Gets the witnessScript for an anchor output from the funding public key.
/// The witness in the spending input must be:
/// <BIP 143 funding_signature>
/// After 16 blocks of confirmation, an alternative satisfying witness could be:
/// <>
/// (empty vector required to satisfy compliance with MINIMALIF-standard rule)
#[inline]
pub fn get_anchor_redeemscript(funding_pubkey: &PublicKey) -> Script {
        Builder::new().push_slice(&funding_pubkey.serialize()[..])
                .push_opcode(opcodes::all::OP_CHECKSIG)
                .push_opcode(opcodes::all::OP_IFDUP)
                .push_opcode(opcodes::all::OP_NOTIF)
                .push_int(16)
                .push_opcode(opcodes::all::OP_CSV)
                .push_opcode(opcodes::all::OP_ENDIF)
                .into_script()
}

/// Per-channel data used to build transactions in conjunction with the per-commitment data (CommitmentTransaction).
/// The fields are organized by holder/counterparty.
///
/// Normally, this is converted to the broadcaster/countersignatory-organized DirectedChannelTransactionParameters
/// before use, via the as_holder_broadcastable and as_counterparty_broadcastable functions.
#[derive(Clone)]
pub struct ChannelTransactionParameters {
        /// Holder public keys
        pub holder_pubkeys: ChannelPublicKeys,
        /// The contest delay selected by the holder, which applies to counterparty-broadcast transactions
        pub holder_selected_contest_delay: u16,
        /// Whether the holder is the initiator of this channel.
        /// This is an input to the commitment number obscure factor computation.
        pub is_outbound_from_holder: bool,
        /// The late-bound counterparty channel transaction parameters.
        /// These parameters are populated at the point in the protocol where the counterparty provides them.
        pub counterparty_parameters: Option<CounterpartyChannelTransactionParameters>,
        /// The late-bound funding outpoint
        pub funding_outpoint: Option<chain::transaction::OutPoint>,
        /// Are anchors (zero fee HTLC transaction variant) used for this channel. Boolean is
        /// serialization backwards-compatible.
        pub opt_anchors: Option<()>
}

/// Late-bound per-channel counterparty data used to build transactions.
#[derive(Clone)]
pub struct CounterpartyChannelTransactionParameters {
        /// Counter-party public keys
        pub pubkeys: ChannelPublicKeys,
        /// The contest delay selected by the counterparty, which applies to holder-broadcast transactions
        pub selected_contest_delay: u16,
}

impl ChannelTransactionParameters {
        /// Whether the late bound parameters are populated.
        pub fn is_populated(&self) -> bool {
                self.counterparty_parameters.is_some() && self.funding_outpoint.is_some()
        }

        /// Convert the holder/counterparty parameters to broadcaster/countersignatory-organized parameters,
        /// given that the holder is the broadcaster.
        ///
        /// self.is_populated() must be true before calling this function.
        pub fn as_holder_broadcastable(&self) -> DirectedChannelTransactionParameters {
                assert!(self.is_populated(), "self.late_parameters must be set before using as_holder_broadcastable");
                DirectedChannelTransactionParameters {
                        inner: self,
                        holder_is_broadcaster: true
                }
        }

        /// Convert the holder/counterparty parameters to broadcaster/countersignatory-organized parameters,
        /// given that the counterparty is the broadcaster.
        ///
        /// self.is_populated() must be true before calling this function.
        pub fn as_counterparty_broadcastable(&self) -> DirectedChannelTransactionParameters {
                assert!(self.is_populated(), "self.late_parameters must be set before using as_counterparty_broadcastable");
                DirectedChannelTransactionParameters {
                        inner: self,
                        holder_is_broadcaster: false
                }
        }
}

impl_writeable_tlv_based!(CounterpartyChannelTransactionParameters, {
        (0, pubkeys, required),
        (2, selected_contest_delay, required),
});

impl_writeable_tlv_based!(ChannelTransactionParameters, {
        (0, holder_pubkeys, required),
        (2, holder_selected_contest_delay, required),
        (4, is_outbound_from_holder, required),
        (6, counterparty_parameters, option),
        (8, funding_outpoint, option),
        (10, opt_anchors, option),
});

/// Static channel fields used to build transactions given per-commitment fields, organized by
/// broadcaster/countersignatory.
///
/// This is derived from the holder/counterparty-organized ChannelTransactionParameters via the
/// as_holder_broadcastable and as_counterparty_broadcastable functions.
pub struct DirectedChannelTransactionParameters<'a> {
        /// The holder's channel static parameters
        inner: &'a ChannelTransactionParameters,
        /// Whether the holder is the broadcaster
        holder_is_broadcaster: bool,
}

impl<'a> DirectedChannelTransactionParameters<'a> {
        /// Get the channel pubkeys for the broadcaster
        pub fn broadcaster_pubkeys(&self) -> &ChannelPublicKeys {
                if self.holder_is_broadcaster {
                        &self.inner.holder_pubkeys
                } else {
                        &self.inner.counterparty_parameters.as_ref().unwrap().pubkeys
                }
        }

        /// Get the channel pubkeys for the countersignatory
        pub fn countersignatory_pubkeys(&self) -> &ChannelPublicKeys {
                if self.holder_is_broadcaster {
                        &self.inner.counterparty_parameters.as_ref().unwrap().pubkeys
                } else {
                        &self.inner.holder_pubkeys
                }
        }

        /// Get the contest delay applicable to the transactions.
        /// Note that the contest delay was selected by the countersignatory.
        pub fn contest_delay(&self) -> u16 {
                let counterparty_parameters = self.inner.counterparty_parameters.as_ref().unwrap();
                if self.holder_is_broadcaster { counterparty_parameters.selected_contest_delay } else { self.inner.holder_selected_contest_delay }
        }

        /// Whether the channel is outbound from the broadcaster.
        ///
        /// The boolean representing the side that initiated the channel is
        /// an input to the commitment number obscure factor computation.
        pub fn is_outbound(&self) -> bool {
                if self.holder_is_broadcaster { self.inner.is_outbound_from_holder } else { !self.inner.is_outbound_from_holder }
        }

        /// The funding outpoint
        pub fn funding_outpoint(&self) -> OutPoint {
                self.inner.funding_outpoint.unwrap().into_bitcoin_outpoint()
        }

        /// Whether to use anchors for this channel
        pub fn opt_anchors(&self) -> bool {
                self.inner.opt_anchors.is_some()
        }
}

/// Information needed to build and sign a holder's commitment transaction.
///
/// The transaction is only signed once we are ready to broadcast.
#[derive(Clone)]
pub struct HolderCommitmentTransaction {
        inner: CommitmentTransaction,
        /// Our counterparty's signature for the transaction
        pub counterparty_sig: Signature,
        /// All non-dust counterparty HTLC signatures, in the order they appear in the transaction
        pub counterparty_htlc_sigs: Vec<Signature>,
        // Which order the signatures should go in when constructing the final commitment tx witness.
        // The user should be able to reconstruct this themselves, so we don't bother to expose it.
        holder_sig_first: bool,
}

impl Deref for HolderCommitmentTransaction {
        type Target = CommitmentTransaction;

        fn deref(&self) -> &Self::Target { &self.inner }
}

impl PartialEq for HolderCommitmentTransaction {
        // We dont care whether we are signed in equality comparison
        fn eq(&self, o: &Self) -> bool {
                self.inner == o.inner
        }
}

impl_writeable_tlv_based!(HolderCommitmentTransaction, {
        (0, inner, required),
        (2, counterparty_sig, required),
        (4, holder_sig_first, required),
        (6, counterparty_htlc_sigs, vec_type),
});

impl HolderCommitmentTransaction {
        #[cfg(test)]
        pub fn dummy() -> Self {
                let secp_ctx = Secp256k1::new();
                let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let dummy_sig = sign(&secp_ctx, &secp256k1::Message::from_slice(&[42; 32]).unwrap(), &SecretKey::from_slice(&[42; 32]).unwrap());

                let keys = TxCreationKeys {
                        per_commitment_point: dummy_key.clone(),
                        revocation_key: dummy_key.clone(),
                        broadcaster_htlc_key: dummy_key.clone(),
                        countersignatory_htlc_key: dummy_key.clone(),
                        broadcaster_delayed_payment_key: dummy_key.clone(),
                };
                let channel_pubkeys = ChannelPublicKeys {
                        funding_pubkey: dummy_key.clone(),
                        revocation_basepoint: dummy_key.clone(),
                        payment_point: dummy_key.clone(),
                        delayed_payment_basepoint: dummy_key.clone(),
                        htlc_basepoint: dummy_key.clone()
                };
                let channel_parameters = ChannelTransactionParameters {
                        holder_pubkeys: channel_pubkeys.clone(),
                        holder_selected_contest_delay: 0,
                        is_outbound_from_holder: false,
                        counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: channel_pubkeys.clone(), selected_contest_delay: 0 }),
                        funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
                        opt_anchors: None
                };
                let mut htlcs_with_aux: Vec<(_, ())> = Vec::new();
                let inner = CommitmentTransaction::new_with_auxiliary_htlc_data(0, 0, 0, false, dummy_key.clone(), dummy_key.clone(), keys, 0, &mut htlcs_with_aux, &channel_parameters.as_counterparty_broadcastable());
                HolderCommitmentTransaction {
                        inner,
                        counterparty_sig: dummy_sig,
                        counterparty_htlc_sigs: Vec::new(),
                        holder_sig_first: false
                }
        }

        /// Create a new holder transaction with the given counterparty signatures.
        /// The funding keys are used to figure out which signature should go first when building the transaction for broadcast.
        pub fn new(commitment_tx: CommitmentTransaction, counterparty_sig: Signature, counterparty_htlc_sigs: Vec<Signature>, holder_funding_key: &PublicKey, counterparty_funding_key: &PublicKey) -> Self {
                Self {
                        inner: commitment_tx,
                        counterparty_sig,
                        counterparty_htlc_sigs,
                        holder_sig_first: holder_funding_key.serialize()[..] < counterparty_funding_key.serialize()[..],
                }
        }

        pub(crate) fn add_holder_sig(&self, funding_redeemscript: &Script, holder_sig: Signature) -> Transaction {
                // First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element.
                let mut tx = self.inner.built.transaction.clone();
                tx.input[0].witness.push(Vec::new());
                let mut ser_holder_sig = holder_sig.serialize_der().to_vec();
                ser_holder_sig.push(EcdsaSighashType::All as u8);
                let mut ser_cp_sig = self.counterparty_sig.serialize_der().to_vec();
                ser_cp_sig.push(EcdsaSighashType::All as u8);

                if self.holder_sig_first {
                        tx.input[0].witness.push(ser_holder_sig);
                        tx.input[0].witness.push(ser_cp_sig);
                } else {
                        tx.input[0].witness.push(ser_cp_sig);
                        tx.input[0].witness.push(ser_holder_sig);
                }

                tx.input[0].witness.push(funding_redeemscript.as_bytes().to_vec());
                tx
        }
}

/// A pre-built Bitcoin commitment transaction and its txid.
#[derive(Clone)]
pub struct BuiltCommitmentTransaction {
        /// The commitment transaction
        pub transaction: Transaction,
        /// The txid for the commitment transaction.
        ///
        /// This is provided as a performance optimization, instead of calling transaction.txid()
        /// multiple times.
        pub txid: Txid,
}

impl_writeable_tlv_based!(BuiltCommitmentTransaction, {
        (0, transaction, required),
        (2, txid, required),
});

impl BuiltCommitmentTransaction {
        /// Get the SIGHASH_ALL sighash value of the transaction.
        ///
        /// This can be used to verify a signature.
        pub fn get_sighash_all(&self, funding_redeemscript: &Script, channel_value_satoshis: u64) -> Message {
                let sighash = &sighash::SighashCache::new(&self.transaction).segwit_signature_hash(0, funding_redeemscript, channel_value_satoshis, EcdsaSighashType::All).unwrap()[..];
                hash_to_message!(sighash)
        }

        /// Sign a transaction, either because we are counter-signing the counterparty's transaction or
        /// because we are about to broadcast a holder transaction.
        pub fn sign<T: secp256k1::Signing>(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1<T>) -> Signature {
                let sighash = self.get_sighash_all(funding_redeemscript, channel_value_satoshis);
                sign(secp_ctx, &sighash, funding_key)
        }
}

/// This class tracks the per-transaction information needed to build a closing transaction and will
/// actually build it and sign.
///
/// This class can be used inside a signer implementation to generate a signature given the relevant
/// secret key.
#[derive(Clone, Hash, PartialEq)]
pub struct ClosingTransaction {
        to_holder_value_sat: u64,
        to_counterparty_value_sat: u64,
        to_holder_script: Script,
        to_counterparty_script: Script,
        built: Transaction,
}

impl ClosingTransaction {
        /// Construct an object of the class
        pub fn new(
                to_holder_value_sat: u64,
                to_counterparty_value_sat: u64,
                to_holder_script: Script,
                to_counterparty_script: Script,
                funding_outpoint: OutPoint,
        ) -> Self {
                let built = build_closing_transaction(
                        to_holder_value_sat, to_counterparty_value_sat,
                        to_holder_script.clone(), to_counterparty_script.clone(),
                        funding_outpoint
                );
                ClosingTransaction {
                        to_holder_value_sat,
                        to_counterparty_value_sat,
                        to_holder_script,
                        to_counterparty_script,
                        built
                }
        }

        /// Trust our pre-built transaction.
        ///
        /// Applies a wrapper which allows access to the transaction.
        ///
        /// This should only be used if you fully trust the builder of this object. It should not
        /// be used by an external signer - instead use the verify function.
        pub fn trust(&self) -> TrustedClosingTransaction {
                TrustedClosingTransaction { inner: self }
        }

        /// Verify our pre-built transaction.
        ///
        /// Applies a wrapper which allows access to the transaction.
        ///
        /// An external validating signer must call this method before signing
        /// or using the built transaction.
        pub fn verify(&self, funding_outpoint: OutPoint) -> Result<TrustedClosingTransaction, ()> {
                let built = build_closing_transaction(
                        self.to_holder_value_sat, self.to_counterparty_value_sat,
                        self.to_holder_script.clone(), self.to_counterparty_script.clone(),
                        funding_outpoint
                );
                if self.built != built {
                        return Err(())
                }
                Ok(TrustedClosingTransaction { inner: self })
        }

        /// The value to be sent to the holder, or zero if the output will be omitted
        pub fn to_holder_value_sat(&self) -> u64 {
                self.to_holder_value_sat
        }

        /// The value to be sent to the counterparty, or zero if the output will be omitted
        pub fn to_counterparty_value_sat(&self) -> u64 {
                self.to_counterparty_value_sat
        }

        /// The destination of the holder's output
        pub fn to_holder_script(&self) -> &Script {
                &self.to_holder_script
        }

        /// The destination of the counterparty's output
        pub fn to_counterparty_script(&self) -> &Script {
                &self.to_counterparty_script
        }
}

/// A wrapper on ClosingTransaction indicating that the built bitcoin
/// transaction is trusted.
///
/// See trust() and verify() functions on CommitmentTransaction.
///
/// This structure implements Deref.
pub struct TrustedClosingTransaction<'a> {
        inner: &'a ClosingTransaction,
}

impl<'a> Deref for TrustedClosingTransaction<'a> {
        type Target = ClosingTransaction;

        fn deref(&self) -> &Self::Target { self.inner }
}

impl<'a> TrustedClosingTransaction<'a> {
        /// The pre-built Bitcoin commitment transaction
        pub fn built_transaction(&self) -> &Transaction {
                &self.inner.built
        }

        /// Get the SIGHASH_ALL sighash value of the transaction.
        ///
        /// This can be used to verify a signature.
        pub fn get_sighash_all(&self, funding_redeemscript: &Script, channel_value_satoshis: u64) -> Message {
                let sighash = &sighash::SighashCache::new(&self.inner.built).segwit_signature_hash(0, funding_redeemscript, channel_value_satoshis, EcdsaSighashType::All).unwrap()[..];
                hash_to_message!(sighash)
        }

        /// Sign a transaction, either because we are counter-signing the counterparty's transaction or
        /// because we are about to broadcast a holder transaction.
        pub fn sign<T: secp256k1::Signing>(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1<T>) -> Signature {
                let sighash = self.get_sighash_all(funding_redeemscript, channel_value_satoshis);
                sign(secp_ctx, &sighash, funding_key)
        }
}

/// This class tracks the per-transaction information needed to build a commitment transaction and will
/// actually build it and sign.  It is used for holder transactions that we sign only when needed
/// and for transactions we sign for the counterparty.
///
/// This class can be used inside a signer implementation to generate a signature given the relevant
/// secret key.
#[derive(Clone)]
pub struct CommitmentTransaction {
        commitment_number: u64,
        to_broadcaster_value_sat: u64,
        to_countersignatory_value_sat: u64,
        feerate_per_kw: u32,
        htlcs: Vec<HTLCOutputInCommitment>,
        // A boolean that is serialization backwards-compatible
        opt_anchors: Option<()>,
        // A cache of the parties' pubkeys required to construct the transaction, see doc for trust()
        keys: TxCreationKeys,
        // For access to the pre-built transaction, see doc for trust()
        built: BuiltCommitmentTransaction,
}

impl PartialEq for CommitmentTransaction {
        fn eq(&self, o: &Self) -> bool {
                let eq = self.commitment_number == o.commitment_number &&
                        self.to_broadcaster_value_sat == o.to_broadcaster_value_sat &&
                        self.to_countersignatory_value_sat == o.to_countersignatory_value_sat &&
                        self.feerate_per_kw == o.feerate_per_kw &&
                        self.htlcs == o.htlcs &&
                        self.opt_anchors == o.opt_anchors &&
                        self.keys == o.keys;
                if eq {
                        debug_assert_eq!(self.built.transaction, o.built.transaction);
                        debug_assert_eq!(self.built.txid, o.built.txid);
                }
                eq
        }
}

impl_writeable_tlv_based!(CommitmentTransaction, {
        (0, commitment_number, required),
        (2, to_broadcaster_value_sat, required),
        (4, to_countersignatory_value_sat, required),
        (6, feerate_per_kw, required),
        (8, keys, required),
        (10, built, required),
        (12, htlcs, vec_type),
        (14, opt_anchors, option),
});

impl CommitmentTransaction {
        /// Construct an object of the class while assigning transaction output indices to HTLCs.
        ///
        /// Populates HTLCOutputInCommitment.transaction_output_index in htlcs_with_aux.
        ///
        /// The generic T allows the caller to match the HTLC output index with auxiliary data.
        /// This auxiliary data is not stored in this object.
        ///
        /// Only include HTLCs that are above the dust limit for the channel.
        ///
        /// (C-not exported) due to the generic though we likely should expose a version without
        pub fn new_with_auxiliary_htlc_data<T>(commitment_number: u64, to_broadcaster_value_sat: u64, to_countersignatory_value_sat: u64, opt_anchors: bool, broadcaster_funding_key: PublicKey, countersignatory_funding_key: PublicKey, keys: TxCreationKeys, feerate_per_kw: u32, htlcs_with_aux: &mut Vec<(HTLCOutputInCommitment, T)>, channel_parameters: &DirectedChannelTransactionParameters) -> CommitmentTransaction {
                // Sort outputs and populate output indices while keeping track of the auxiliary data
                let (outputs, htlcs) = Self::internal_build_outputs(&keys, to_broadcaster_value_sat, to_countersignatory_value_sat, htlcs_with_aux, channel_parameters, opt_anchors, &broadcaster_funding_key, &countersignatory_funding_key).unwrap();

                let (obscured_commitment_transaction_number, txins) = Self::internal_build_inputs(commitment_number, channel_parameters);
                let transaction = Self::make_transaction(obscured_commitment_transaction_number, txins, outputs);
                let txid = transaction.txid();
                CommitmentTransaction {
                        commitment_number,
                        to_broadcaster_value_sat,
                        to_countersignatory_value_sat,
                        feerate_per_kw,
                        htlcs,
                        opt_anchors: if opt_anchors { Some(()) } else { None },
                        keys,
                        built: BuiltCommitmentTransaction {
                                transaction,
                                txid
                        },
                }
        }

        fn internal_rebuild_transaction(&self, keys: &TxCreationKeys, channel_parameters: &DirectedChannelTransactionParameters, broadcaster_funding_key: &PublicKey, countersignatory_funding_key: &PublicKey) -> Result<BuiltCommitmentTransaction, ()> {
                let (obscured_commitment_transaction_number, txins) = Self::internal_build_inputs(self.commitment_number, channel_parameters);

                let mut htlcs_with_aux = self.htlcs.iter().map(|h| (h.clone(), ())).collect();
                let (outputs, _) = Self::internal_build_outputs(keys, self.to_broadcaster_value_sat, self.to_countersignatory_value_sat, &mut htlcs_with_aux, channel_parameters, self.opt_anchors.is_some(), broadcaster_funding_key, countersignatory_funding_key)?;

                let transaction = Self::make_transaction(obscured_commitment_transaction_number, txins, outputs);
                let txid = transaction.txid();
                let built_transaction = BuiltCommitmentTransaction {
                        transaction,
                        txid
                };
                Ok(built_transaction)
        }

        fn make_transaction(obscured_commitment_transaction_number: u64, txins: Vec<TxIn>, outputs: Vec<TxOut>) -> Transaction {
                Transaction {
                        version: 2,
                        lock_time: PackedLockTime(((0x20 as u32) << 8 * 3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32)),
                        input: txins,
                        output: outputs,
                }
        }

        // This is used in two cases:
        // - initial sorting of outputs / HTLCs in the constructor, in which case T is auxiliary data the
        //   caller needs to have sorted together with the HTLCs so it can keep track of the output index
        // - building of a bitcoin transaction during a verify() call, in which case T is just ()
        fn internal_build_outputs<T>(keys: &TxCreationKeys, to_broadcaster_value_sat: u64, to_countersignatory_value_sat: u64, htlcs_with_aux: &mut Vec<(HTLCOutputInCommitment, T)>, channel_parameters: &DirectedChannelTransactionParameters, opt_anchors: bool, broadcaster_funding_key: &PublicKey, countersignatory_funding_key: &PublicKey) -> Result<(Vec<TxOut>, Vec<HTLCOutputInCommitment>), ()> {
                let countersignatory_pubkeys = channel_parameters.countersignatory_pubkeys();
                let contest_delay = channel_parameters.contest_delay();

                let mut txouts: Vec<(TxOut, Option<&mut HTLCOutputInCommitment>)> = Vec::new();

                if to_countersignatory_value_sat > 0 {
                        let script = if opt_anchors {
                            get_to_countersignatory_with_anchors_redeemscript(&countersignatory_pubkeys.payment_point).to_v0_p2wsh()
                        } else {
                            get_p2wpkh_redeemscript(&countersignatory_pubkeys.payment_point)
                        };
                        txouts.push((
                                TxOut {
                                        script_pubkey: script.clone(),
                                        value: to_countersignatory_value_sat,
                                },
                                None,
                        ))
                }

                if to_broadcaster_value_sat > 0 {
                        let redeem_script = get_revokeable_redeemscript(
                                &keys.revocation_key,
                                contest_delay,
                                &keys.broadcaster_delayed_payment_key,
                        );
                        txouts.push((
                                TxOut {
                                        script_pubkey: redeem_script.to_v0_p2wsh(),
                                        value: to_broadcaster_value_sat,
                                },
                                None,
                        ));
                }

                if opt_anchors {
                        if to_broadcaster_value_sat > 0 || !htlcs_with_aux.is_empty() {
                                let anchor_script = get_anchor_redeemscript(broadcaster_funding_key);
                                txouts.push((
                                        TxOut {
                                                script_pubkey: anchor_script.to_v0_p2wsh(),
                                                value: ANCHOR_OUTPUT_VALUE_SATOSHI,
                                        },
                                        None,
                                ));
                        }

                        if to_countersignatory_value_sat > 0 || !htlcs_with_aux.is_empty() {
                                let anchor_script = get_anchor_redeemscript(countersignatory_funding_key);
                                txouts.push((
                                        TxOut {
                                                script_pubkey: anchor_script.to_v0_p2wsh(),
                                                value: ANCHOR_OUTPUT_VALUE_SATOSHI,
                                        },
                                        None,
                                ));
                        }
                }

                let mut htlcs = Vec::with_capacity(htlcs_with_aux.len());
                for (htlc, _) in htlcs_with_aux {
                        let script = chan_utils::get_htlc_redeemscript(&htlc, opt_anchors, &keys);
                        let txout = TxOut {
                                script_pubkey: script.to_v0_p2wsh(),
                                value: htlc.amount_msat / 1000,
                        };
                        txouts.push((txout, Some(htlc)));
                }

                // Sort output in BIP-69 order (amount, scriptPubkey).  Tie-breaks based on HTLC
                // CLTV expiration height.
                sort_outputs(&mut txouts, |a, b| {
                        if let &Some(ref a_htlcout) = a {
                                if let &Some(ref b_htlcout) = b {
                                        a_htlcout.cltv_expiry.cmp(&b_htlcout.cltv_expiry)
                                                // Note that due to hash collisions, we have to have a fallback comparison
                                                // here for fuzzing mode (otherwise at least chanmon_fail_consistency
                                                // may fail)!
                                                .then(a_htlcout.payment_hash.0.cmp(&b_htlcout.payment_hash.0))
                                // For non-HTLC outputs, if they're copying our SPK we don't really care if we
                                // close the channel due to mismatches - they're doing something dumb:
                                } else { cmp::Ordering::Equal }
                        } else { cmp::Ordering::Equal }
                });

                let mut outputs = Vec::with_capacity(txouts.len());
                for (idx, out) in txouts.drain(..).enumerate() {
                        if let Some(htlc) = out.1 {
                                htlc.transaction_output_index = Some(idx as u32);
                                htlcs.push(htlc.clone());
                        }
                        outputs.push(out.0);
                }
                Ok((outputs, htlcs))
        }

        fn internal_build_inputs(commitment_number: u64, channel_parameters: &DirectedChannelTransactionParameters) -> (u64, Vec<TxIn>) {
                let broadcaster_pubkeys = channel_parameters.broadcaster_pubkeys();
                let countersignatory_pubkeys = channel_parameters.countersignatory_pubkeys();
                let commitment_transaction_number_obscure_factor = get_commitment_transaction_number_obscure_factor(
                        &broadcaster_pubkeys.payment_point,
                        &countersignatory_pubkeys.payment_point,
                        channel_parameters.is_outbound(),
                );

                let obscured_commitment_transaction_number =
                        commitment_transaction_number_obscure_factor ^ (INITIAL_COMMITMENT_NUMBER - commitment_number);

                let txins = {
                        let mut ins: Vec<TxIn> = Vec::new();
                        ins.push(TxIn {
                                previous_output: channel_parameters.funding_outpoint(),
                                script_sig: Script::new(),
                                sequence: Sequence(((0x80 as u32) << 8 * 3)
                                        | ((obscured_commitment_transaction_number >> 3 * 8) as u32)),
                                witness: Witness::new(),
                        });
                        ins
                };
                (obscured_commitment_transaction_number, txins)
        }

        /// The backwards-counting commitment number
        pub fn commitment_number(&self) -> u64 {
                self.commitment_number
        }

        /// The value to be sent to the broadcaster
        pub fn to_broadcaster_value_sat(&self) -> u64 {
                self.to_broadcaster_value_sat
        }

        /// The value to be sent to the counterparty
        pub fn to_countersignatory_value_sat(&self) -> u64 {
                self.to_countersignatory_value_sat
        }

        /// The feerate paid per 1000-weight-unit in this commitment transaction.
        pub fn feerate_per_kw(&self) -> u32 {
                self.feerate_per_kw
        }

        /// The non-dust HTLCs (direction, amt, height expiration, hash, transaction output index)
        /// which were included in this commitment transaction in output order.
        /// The transaction index is always populated.
        ///
        /// (C-not exported) as we cannot currently convert Vec references to/from C, though we should
        /// expose a less effecient version which creates a Vec of references in the future.
        pub fn htlcs(&self) -> &Vec<HTLCOutputInCommitment> {
                &self.htlcs
        }

        /// Trust our pre-built transaction and derived transaction creation public keys.
        ///
        /// Applies a wrapper which allows access to these fields.
        ///
        /// This should only be used if you fully trust the builder of this object.  It should not
        /// be used by an external signer - instead use the verify function.
        pub fn trust(&self) -> TrustedCommitmentTransaction {
                TrustedCommitmentTransaction { inner: self }
        }

        /// Verify our pre-built transaction and derived transaction creation public keys.
        ///
        /// Applies a wrapper which allows access to these fields.
        ///
        /// An external validating signer must call this method before signing
        /// or using the built transaction.
        pub fn verify<T: secp256k1::Signing + secp256k1::Verification>(&self, channel_parameters: &DirectedChannelTransactionParameters, broadcaster_keys: &ChannelPublicKeys, countersignatory_keys: &ChannelPublicKeys, secp_ctx: &Secp256k1<T>) -> Result<TrustedCommitmentTransaction, ()> {
                // This is the only field of the key cache that we trust
                let per_commitment_point = self.keys.per_commitment_point;
                let keys = TxCreationKeys::from_channel_static_keys(&per_commitment_point, broadcaster_keys, countersignatory_keys, secp_ctx).unwrap();
                if keys != self.keys {
                        return Err(());
                }
                let tx = self.internal_rebuild_transaction(&keys, channel_parameters, &broadcaster_keys.funding_pubkey, &countersignatory_keys.funding_pubkey)?;
                if self.built.transaction != tx.transaction || self.built.txid != tx.txid {
                        return Err(());
                }
                Ok(TrustedCommitmentTransaction { inner: self })
        }
}

/// A wrapper on CommitmentTransaction indicating that the derived fields (the built bitcoin
/// transaction and the transaction creation keys) are trusted.
///
/// See trust() and verify() functions on CommitmentTransaction.
///
/// This structure implements Deref.
pub struct TrustedCommitmentTransaction<'a> {
        inner: &'a CommitmentTransaction,
}

impl<'a> Deref for TrustedCommitmentTransaction<'a> {
        type Target = CommitmentTransaction;

        fn deref(&self) -> &Self::Target { self.inner }
}

impl<'a> TrustedCommitmentTransaction<'a> {
        /// The transaction ID of the built Bitcoin transaction
        pub fn txid(&self) -> Txid {
                self.inner.built.txid
        }

        /// The pre-built Bitcoin commitment transaction
        pub fn built_transaction(&self) -> &BuiltCommitmentTransaction {
                &self.inner.built
        }

        /// The pre-calculated transaction creation public keys.
        pub fn keys(&self) -> &TxCreationKeys {
                &self.inner.keys
        }

        /// Should anchors be used.
        pub fn opt_anchors(&self) -> bool {
                self.opt_anchors.is_some()
        }

        /// Get a signature for each HTLC which was included in the commitment transaction (ie for
        /// which HTLCOutputInCommitment::transaction_output_index.is_some()).
        ///
        /// The returned Vec has one entry for each HTLC, and in the same order.
        ///
        /// This function is only valid in the holder commitment context, it always uses EcdsaSighashType::All.
        pub fn get_htlc_sigs<T: secp256k1::Signing>(&self, htlc_base_key: &SecretKey, channel_parameters: &DirectedChannelTransactionParameters, secp_ctx: &Secp256k1<T>) -> Result<Vec<Signature>, ()> {
                let inner = self.inner;
                let keys = &inner.keys;
                let txid = inner.built.txid;
                let mut ret = Vec::with_capacity(inner.htlcs.len());
                let holder_htlc_key = derive_private_key(secp_ctx, &inner.keys.per_commitment_point, htlc_base_key).map_err(|_| ())?;

                for this_htlc in inner.htlcs.iter() {
                        assert!(this_htlc.transaction_output_index.is_some());
                        let htlc_tx = build_htlc_transaction(&txid, inner.feerate_per_kw, channel_parameters.contest_delay(), &this_htlc, self.opt_anchors(), &keys.broadcaster_delayed_payment_key, &keys.revocation_key);

                        let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc, self.opt_anchors(), &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key);

                        let sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, EcdsaSighashType::All).unwrap()[..]);
                        ret.push(sign(secp_ctx, &sighash, &holder_htlc_key));
                }
                Ok(ret)
        }

        /// Gets a signed HTLC transaction given a preimage (for !htlc.offered) and the holder HTLC transaction signature.
        pub(crate) fn get_signed_htlc_tx(&self, channel_parameters: &DirectedChannelTransactionParameters, htlc_index: usize, counterparty_signature: &Signature, signature: &Signature, preimage: &Option<PaymentPreimage>) -> Transaction {
                let inner = self.inner;
                let keys = &inner.keys;
                let txid = inner.built.txid;
                let this_htlc = &inner.htlcs[htlc_index];
                assert!(this_htlc.transaction_output_index.is_some());
                // if we don't have preimage for an HTLC-Success, we can't generate an HTLC transaction.
                if !this_htlc.offered && preimage.is_none() { unreachable!(); }
                // Further, we should never be provided the preimage for an HTLC-Timeout transaction.
                if  this_htlc.offered && preimage.is_some() { unreachable!(); }

                let mut htlc_tx = build_htlc_transaction(&txid, inner.feerate_per_kw, channel_parameters.contest_delay(), &this_htlc, self.opt_anchors(), &keys.broadcaster_delayed_payment_key, &keys.revocation_key);

                let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc, self.opt_anchors(), &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key);

                let sighashtype = if self.opt_anchors() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };

                // First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element.
                htlc_tx.input[0].witness.push(Vec::new());

                let mut cp_sig_ser = counterparty_signature.serialize_der().to_vec();
                cp_sig_ser.push(sighashtype as u8);
                htlc_tx.input[0].witness.push(cp_sig_ser);
                let mut holder_sig_ser = signature.serialize_der().to_vec();
                holder_sig_ser.push(EcdsaSighashType::All as u8);
                htlc_tx.input[0].witness.push(holder_sig_ser);

                if this_htlc.offered {
                        // Due to BIP146 (MINIMALIF) this must be a zero-length element to relay.
                        htlc_tx.input[0].witness.push(Vec::new());
                } else {
                        htlc_tx.input[0].witness.push(preimage.unwrap().0.to_vec());
                }

                htlc_tx.input[0].witness.push(htlc_redeemscript.as_bytes().to_vec());
                htlc_tx
        }
}

/// Commitment transaction numbers which appear in the transactions themselves are XOR'd with a
/// shared secret first. This prevents on-chain observers from discovering how many commitment
/// transactions occurred in a channel before it was closed.
///
/// This function gets the shared secret from relevant channel public keys and can be used to
/// "decrypt" the commitment transaction number given a commitment transaction on-chain.
pub fn get_commitment_transaction_number_obscure_factor(
        broadcaster_payment_basepoint: &PublicKey,
        countersignatory_payment_basepoint: &PublicKey,
        outbound_from_broadcaster: bool,
) -> u64 {
        let mut sha = Sha256::engine();

        if outbound_from_broadcaster {
                sha.input(&broadcaster_payment_basepoint.serialize());
                sha.input(&countersignatory_payment_basepoint.serialize());
        } else {
                sha.input(&countersignatory_payment_basepoint.serialize());
                sha.input(&broadcaster_payment_basepoint.serialize());
        }
        let res = Sha256::from_engine(sha).into_inner();

        ((res[26] as u64) << 5 * 8)
                | ((res[27] as u64) << 4 * 8)
                | ((res[28] as u64) << 3 * 8)
                | ((res[29] as u64) << 2 * 8)
                | ((res[30] as u64) << 1 * 8)
                | ((res[31] as u64) << 0 * 8)
}

fn get_p2wpkh_redeemscript(key: &PublicKey) -> Script {
        Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
                .push_slice(&WPubkeyHash::hash(&key.serialize())[..])
                .into_script()
}

#[cfg(test)]
mod tests {
        use super::CounterpartyCommitmentSecrets;
        use ::{hex, chain};
        use prelude::*;
        use ln::chan_utils::{get_htlc_redeemscript, get_to_countersignatory_with_anchors_redeemscript, get_p2wpkh_redeemscript, CommitmentTransaction, TxCreationKeys, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, HTLCOutputInCommitment};
        use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
        use util::test_utils;
        use chain::keysinterface::{KeysInterface, BaseSign};
        use bitcoin::{Network, Txid};
        use bitcoin::hashes::Hash;
        use ln::PaymentHash;
        use bitcoin::hashes::hex::ToHex;

        #[test]
        fn test_anchors() {
                let secp_ctx = Secp256k1::new();

                let seed = [42; 32];
                let network = Network::Testnet;
                let keys_provider = test_utils::TestKeysInterface::new(&seed, network);
                let signer = keys_provider.get_channel_signer(false, 3000);
                let counterparty_signer = keys_provider.get_channel_signer(false, 3000);
                let delayed_payment_base = &signer.pubkeys().delayed_payment_basepoint;
                let per_commitment_secret = SecretKey::from_slice(&hex::decode("1f1e1d1c1b1a191817161514131211100f0e0d0c0b0a09080706050403020100").unwrap()[..]).unwrap();
                let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);
                let htlc_basepoint = &signer.pubkeys().htlc_basepoint;
                let holder_pubkeys = signer.pubkeys();
                let counterparty_pubkeys = counterparty_signer.pubkeys();
                let keys = TxCreationKeys::derive_new(&secp_ctx, &per_commitment_point, delayed_payment_base, htlc_basepoint, &counterparty_pubkeys.revocation_basepoint, &counterparty_pubkeys.htlc_basepoint).unwrap();
                let mut channel_parameters = ChannelTransactionParameters {
                        holder_pubkeys: holder_pubkeys.clone(),
                        holder_selected_contest_delay: 0,
                        is_outbound_from_holder: false,
                        counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: counterparty_pubkeys.clone(), selected_contest_delay: 0 }),
                        funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
                        opt_anchors: None
                };

                let mut htlcs_with_aux: Vec<(_, ())> = Vec::new();

                // Generate broadcaster and counterparty outputs
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 1000, 2000,
                        false,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 2);
                assert_eq!(tx.built.transaction.output[1].script_pubkey, get_p2wpkh_redeemscript(&counterparty_pubkeys.payment_point));

                // Generate broadcaster and counterparty outputs as well as two anchors
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 1000, 2000,
                        true,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 4);
                assert_eq!(tx.built.transaction.output[3].script_pubkey, get_to_countersignatory_with_anchors_redeemscript(&counterparty_pubkeys.payment_point).to_v0_p2wsh());

                // Generate broadcaster output and anchor
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 3000, 0,
                        true,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 2);

                // Generate counterparty output and anchor
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 0, 3000,
                        true,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut htlcs_with_aux, &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 2);

                let received_htlc = HTLCOutputInCommitment {
                        offered: false,
                        amount_msat: 400000,
                        cltv_expiry: 100,
                        payment_hash: PaymentHash([42; 32]),
                        transaction_output_index: None,
                };

                let offered_htlc = HTLCOutputInCommitment {
                        offered: true,
                        amount_msat: 600000,
                        cltv_expiry: 100,
                        payment_hash: PaymentHash([43; 32]),
                        transaction_output_index: None,
                };

                // Generate broadcaster output and received and offered HTLC outputs,  w/o anchors
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 3000, 0,
                        false,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut vec![(received_htlc.clone(), ()), (offered_htlc.clone(), ())],
                        &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 3);
                assert_eq!(tx.built.transaction.output[0].script_pubkey, get_htlc_redeemscript(&received_htlc, false, &keys).to_v0_p2wsh());
                assert_eq!(tx.built.transaction.output[1].script_pubkey, get_htlc_redeemscript(&offered_htlc, false, &keys).to_v0_p2wsh());
                assert_eq!(get_htlc_redeemscript(&received_htlc, false, &keys).to_v0_p2wsh().to_hex(),
                                   "002085cf52e41ba7c099a39df504e7b61f6de122971ceb53b06731876eaeb85e8dc5");
                assert_eq!(get_htlc_redeemscript(&offered_htlc, false, &keys).to_v0_p2wsh().to_hex(),
                                   "002049f0736bb335c61a04d2623a24df878a7592a3c51fa7258d41b2c85318265e73");

                // Generate broadcaster output and received and offered HTLC outputs,  with anchors
                channel_parameters.opt_anchors = Some(());
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(
                        0, 3000, 0,
                        true,
                        holder_pubkeys.funding_pubkey,
                        counterparty_pubkeys.funding_pubkey,
                        keys.clone(), 1,
                        &mut vec![(received_htlc.clone(), ()), (offered_htlc.clone(), ())],
                        &channel_parameters.as_holder_broadcastable()
                );
                assert_eq!(tx.built.transaction.output.len(), 5);
                assert_eq!(tx.built.transaction.output[2].script_pubkey, get_htlc_redeemscript(&received_htlc, true, &keys).to_v0_p2wsh());
                assert_eq!(tx.built.transaction.output[3].script_pubkey, get_htlc_redeemscript(&offered_htlc, true, &keys).to_v0_p2wsh());
                assert_eq!(get_htlc_redeemscript(&received_htlc, true, &keys).to_v0_p2wsh().to_hex(),
                                   "002067114123af3f95405bae4fd930fc95de03e3c86baaee8b2dd29b43dd26cf613c");
                assert_eq!(get_htlc_redeemscript(&offered_htlc, true, &keys).to_v0_p2wsh().to_hex(),
                                   "0020a06e3b0d4fcf704f2b9c41e16a70099e39989466c3142b8573a1154542f28f57");
        }

        #[test]
        fn test_per_commitment_storage() {
                // Test vectors from BOLT 3:
                let mut secrets: Vec<[u8; 32]> = Vec::new();
                let mut monitor;

                macro_rules! test_secrets {
                        () => {
                                let mut idx = 281474976710655;
                                for secret in secrets.iter() {
                                        assert_eq!(monitor.get_secret(idx).unwrap(), *secret);
                                        idx -= 1;
                                }
                                assert_eq!(monitor.get_min_seen_secret(), idx + 1);
                                assert!(monitor.get_secret(idx).is_none());
                        };
                }

                {
                        // insert_secret correct sequence
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c65716add7aa98ba7acb236352d665cab17345fe45b55fb879ff80e6bd0c41dd").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("969660042a28f32d9be17344e09374b379962d03db1574df5a8a5a47e19ce3f2").unwrap());
                        monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("a5a64476122ca0925fb344bdc1854c1c0a59fc614298e50a33e331980a220f32").unwrap());
                        monitor.provide_secret(281474976710649, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("05cde6323d949933f7f7b78776bcc1ea6d9b31447732e3802e1f7ac44b650e17").unwrap());
                        monitor.provide_secret(281474976710648, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();
                }

                {
                        // insert_secret #1 incorrect
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("02a40c85b6f28da08dfdbe0926c53fab2de6d28c10301f8f7c4073d5e42e3148").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        assert!(monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #2 incorrect (#1 derived from incorrect)
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("02a40c85b6f28da08dfdbe0926c53fab2de6d28c10301f8f7c4073d5e42e3148").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("dddc3a8d14fddf2b68fa8c7fbad2748274937479dd0f8930d5ebb4ab6bd866a3").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        assert!(monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #3 incorrect
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c51a18b13e8527e579ec56365482c62f180b7d5760b46e9477dae59e87ed423a").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        assert!(monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #4 incorrect (1,2,3 derived from incorrect)
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("02a40c85b6f28da08dfdbe0926c53fab2de6d28c10301f8f7c4073d5e42e3148").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("dddc3a8d14fddf2b68fa8c7fbad2748274937479dd0f8930d5ebb4ab6bd866a3").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c51a18b13e8527e579ec56365482c62f180b7d5760b46e9477dae59e87ed423a").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("ba65d7b0ef55a3ba300d4e87af29868f394f8f138d78a7011669c79b37b936f4").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c65716add7aa98ba7acb236352d665cab17345fe45b55fb879ff80e6bd0c41dd").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("969660042a28f32d9be17344e09374b379962d03db1574df5a8a5a47e19ce3f2").unwrap());
                        monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("a5a64476122ca0925fb344bdc1854c1c0a59fc614298e50a33e331980a220f32").unwrap());
                        monitor.provide_secret(281474976710649, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("05cde6323d949933f7f7b78776bcc1ea6d9b31447732e3802e1f7ac44b650e17").unwrap());
                        assert!(monitor.provide_secret(281474976710648, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #5 incorrect
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("631373ad5f9ef654bb3dade742d09504c567edd24320d2fcd68e3cc47e2ff6a6").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("969660042a28f32d9be17344e09374b379962d03db1574df5a8a5a47e19ce3f2").unwrap());
                        assert!(monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #6 incorrect (5 derived from incorrect)
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("631373ad5f9ef654bb3dade742d09504c567edd24320d2fcd68e3cc47e2ff6a6").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("b7e76a83668bde38b373970155c868a653304308f9896692f904a23731224bb1").unwrap());
                        monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("a5a64476122ca0925fb344bdc1854c1c0a59fc614298e50a33e331980a220f32").unwrap());
                        monitor.provide_secret(281474976710649, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("05cde6323d949933f7f7b78776bcc1ea6d9b31447732e3802e1f7ac44b650e17").unwrap());
                        assert!(monitor.provide_secret(281474976710648, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #7 incorrect
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c65716add7aa98ba7acb236352d665cab17345fe45b55fb879ff80e6bd0c41dd").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("969660042a28f32d9be17344e09374b379962d03db1574df5a8a5a47e19ce3f2").unwrap());
                        monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("e7971de736e01da8ed58b94c2fc216cb1dca9e326f3a96e7194fe8ea8af6c0a3").unwrap());
                        monitor.provide_secret(281474976710649, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("05cde6323d949933f7f7b78776bcc1ea6d9b31447732e3802e1f7ac44b650e17").unwrap());
                        assert!(monitor.provide_secret(281474976710648, secrets.last().unwrap().clone()).is_err());
                }

                {
                        // insert_secret #8 incorrect
                        monitor = CounterpartyCommitmentSecrets::new();
                        secrets.clear();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                        monitor.provide_secret(281474976710655, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                        monitor.provide_secret(281474976710654, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                        monitor.provide_secret(281474976710653, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                        monitor.provide_secret(281474976710652, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("c65716add7aa98ba7acb236352d665cab17345fe45b55fb879ff80e6bd0c41dd").unwrap());
                        monitor.provide_secret(281474976710651, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("969660042a28f32d9be17344e09374b379962d03db1574df5a8a5a47e19ce3f2").unwrap());
                        monitor.provide_secret(281474976710650, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("a5a64476122ca0925fb344bdc1854c1c0a59fc614298e50a33e331980a220f32").unwrap());
                        monitor.provide_secret(281474976710649, secrets.last().unwrap().clone()).unwrap();
                        test_secrets!();

                        secrets.push([0; 32]);
                        secrets.last_mut().unwrap()[0..32].clone_from_slice(&hex::decode("a7efbc61aac46d34f77778bac22c8a20c6a46ca460addc49009bda875ec88fa4").unwrap());
                        assert!(monitor.provide_secret(281474976710648, secrets.last().unwrap().clone()).is_err());
                }
        }
}