Modify ecdh to take Scalar
[rust-lightning] / lightning / src / chain / keysinterface.rs
index 7be26634916fbaa5268d264528e7099953d6c03d..73b8a1b98224ace7aef2f6db05a82ca2a020e476 100644 (file)
 //! spendable on-chain outputs which the user owns and is responsible for using just as any other
 //! on-chain output which is theirs.
 
-use bitcoin::blockdata::transaction::{Transaction, TxOut, TxIn, SigHashType};
+use bitcoin::blockdata::transaction::{Transaction, TxOut, TxIn, EcdsaSighashType};
 use bitcoin::blockdata::script::{Script, Builder};
 use bitcoin::blockdata::opcodes;
 use bitcoin::network::constants::Network;
 use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber};
-use bitcoin::util::bip143;
+use bitcoin::util::sighash;
 
+use bitcoin::bech32::u5;
 use bitcoin::hashes::{Hash, HashEngine};
 use bitcoin::hashes::sha256::HashEngine as Sha256State;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hash_types::WPubkeyHash;
 
-use bitcoin::secp256k1::key::{SecretKey, PublicKey};
-use bitcoin::secp256k1::{Secp256k1, Signature, Signing};
-use bitcoin::secp256k1::recovery::RecoverableSignature;
-use bitcoin::secp256k1;
+use bitcoin::secp256k1::{SecretKey, PublicKey, Scalar};
+use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature, Signing};
+use bitcoin::secp256k1::ecdh::SharedSecret;
+use bitcoin::secp256k1::ecdsa::RecoverableSignature;
+use bitcoin::{PackedLockTime, secp256k1, Sequence, Witness};
 
 use util::{byte_utils, transaction_utils};
-use util::ser::{Writeable, Writer, Readable};
+use util::crypto::{hkdf_extract_expand_twice, sign};
+use util::ser::{Writeable, Writer, Readable, ReadableArgs};
 
 use chain::transaction::OutPoint;
-use ln::chan_utils;
+use ln::{chan_utils, PaymentPreimage};
 use ln::chan_utils::{HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys, HolderCommitmentTransaction, ChannelTransactionParameters, CommitmentTransaction, ClosingTransaction};
 use ln::msgs::UnsignedChannelAnnouncement;
 use ln::script::ShutdownScript;
@@ -42,6 +45,13 @@ use prelude::*;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use io::{self, Error};
 use ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+use util::invoice::construct_invoice_preimage;
+
+/// Used as initial key material, to be expanded into multiple secret keys (but not to be used
+/// directly). This is used within LDK to encrypt/decrypt inbound payment data.
+/// (C-not exported) as we just use [u8; 32] directly
+#[derive(Hash, Copy, Clone, PartialEq, Eq, Debug)]
+pub struct KeyMaterial(pub [u8; 32]);
 
 /// Information about a spendable output to a P2WSH script. See
 /// SpendableOutputDescriptor::DelayedPaymentOutput for more details on how to spend this.
@@ -218,7 +228,14 @@ pub trait BaseSign {
        /// secret won't leave us without a broadcastable holder transaction.
        /// Policy checks should be implemented in this function, including checking the amount
        /// sent to us and checking the HTLCs.
-       fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) -> Result<(), ()>;
+       ///
+       /// The preimages of outgoing HTLCs that were fulfilled since the last commitment are provided.
+       /// A validating signer should ensure that an HTLC output is removed only when the matching
+       /// preimage is provided, or when the value to holder is restored.
+       ///
+       /// NOTE: all the relevant preimages will be provided, but there may also be additional
+       /// irrelevant or duplicate preimages.
+       fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction, preimages: Vec<PaymentPreimage>) -> Result<(), ()>;
        /// Gets the holder's channel public keys and basepoints
        fn pubkeys(&self) -> &ChannelPublicKeys;
        /// Gets an arbitrary identifier describing the set of keys which are provided back to you in
@@ -232,9 +249,16 @@ pub trait BaseSign {
        ///
        /// Policy checks should be implemented in this function, including checking the amount
        /// sent to us and checking the HTLCs.
+       ///
+       /// The preimages of outgoing HTLCs that were fulfilled since the last commitment are provided.
+       /// A validating signer should ensure that an HTLC output is removed only when the matching
+       /// preimage is provided, or when the value to holder is restored.
+       ///
+       /// NOTE: all the relevant preimages will be provided, but there may also be additional
+       /// irrelevant or duplicate preimages.
        //
        // TODO: Document the things someone using this interface should enforce before signing.
-       fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()>;
+       fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()>;
        /// Validate the counterparty's revocation.
        ///
        /// This is required in order for the signer to make sure that the state has moved
@@ -324,13 +348,17 @@ pub trait BaseSign {
        /// chosen to forgo their output as dust.
        fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
 
-       /// Signs a channel announcement message with our funding key, proving it comes from one
-       /// of the channel participants.
+       /// Signs a channel announcement message with our funding key and our node secret key (aka
+       /// node_id or network_key), proving it comes from one of the channel participants.
+       ///
+       /// The first returned signature should be from our node secret key, the second from our
+       /// funding key.
        ///
        /// Note that if this fails or is rejected, the channel will not be publicly announced and
        /// our counterparty may (though likely will not) close the channel on us for violating the
        /// protocol.
-       fn sign_channel_announcement(&self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
+       fn sign_channel_announcement(&self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>)
+               -> Result<(Signature, Signature), ()>;
 
        /// Set the counterparty static channel data, including basepoints,
        /// counterparty_selected/holder_selected_contest_delay and funding outpoint.
@@ -353,15 +381,36 @@ pub trait BaseSign {
 pub trait Sign: BaseSign + Writeable + Clone {
 }
 
+/// Specifies the recipient of an invoice, to indicate to [`KeysInterface::sign_invoice`] what node
+/// secret key should be used to sign the invoice.
+pub enum Recipient {
+       /// The invoice should be signed with the local node secret key.
+       Node,
+       /// The invoice should be signed with the phantom node secret key. This secret key must be the
+       /// same for all nodes participating in the [phantom node payment].
+       ///
+       /// [phantom node payment]: PhantomKeysManager
+       PhantomNode,
+}
+
 /// A trait to describe an object which can get user secrets and key material.
 pub trait KeysInterface {
        /// A type which implements Sign which will be returned by get_channel_signer.
        type Signer : Sign;
 
-       /// Get node secret key (aka node_id or network_key).
+       /// Get node secret key based on the provided [`Recipient`].
        ///
-       /// This method must return the same value each time it is called.
-       fn get_node_secret(&self) -> SecretKey;
+       /// The node_id/network_key is the public key that corresponds to this secret key.
+       ///
+       /// This method must return the same value each time it is called with a given `Recipient`
+       /// parameter.
+       fn get_node_secret(&self, recipient: Recipient) -> Result<SecretKey, ()>;
+       /// Gets the ECDH shared secret of our [`node secret`] and `other_key`, multiplying by `tweak` if
+       /// one is provided. Note that this tweak can be applied to `other_key` instead of our node
+       /// secret, though this is less efficient.
+       ///
+       /// [`node secret`]: Self::get_node_secret
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&Scalar>) -> Result<SharedSecret, ()>;
        /// Get a script pubkey which we send funds to when claiming on-chain contestable outputs.
        ///
        /// This method should return a different value each time it is called, to avoid linking
@@ -392,11 +441,28 @@ pub trait KeysInterface {
        /// you've read all of the provided bytes to ensure no corruption occurred.
        fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, DecodeError>;
 
-       /// Sign an invoice's preimage (note that this is the preimage of the invoice, not the HTLC's
-       /// preimage). By parameterizing by the preimage instead of the hash, we allow implementors of
+       /// Sign an invoice.
+       /// By parameterizing by the raw invoice bytes instead of the hash, we allow implementors of
        /// this trait to parse the invoice and make sure they're signing what they expect, rather than
        /// blindly signing the hash.
-       fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()>;
+       /// The hrp is ascii bytes, while the invoice data is base32.
+       ///
+       /// The secret key used to sign the invoice is dependent on the [`Recipient`].
+       fn sign_invoice(&self, hrp_bytes: &[u8], invoice_data: &[u5], receipient: Recipient) -> Result<RecoverableSignature, ()>;
+
+       /// Get secret key material as bytes for use in encrypting and decrypting inbound payment data.
+       ///
+       /// If the implementor of this trait supports [phantom node payments], then every node that is
+       /// intended to be included in the phantom invoice route hints must return the same value from
+       /// this method.
+       //  This is because LDK avoids storing inbound payment data by encrypting payment data in the
+       //  payment hash and/or payment secret, therefore for a payment to be receivable by multiple
+       //  nodes, they must share the key that encrypts this payment data.
+       ///
+       /// This method must return the same value each time it is called.
+       ///
+       /// [phantom node payments]: PhantomKeysManager
+       fn get_inbound_payment_key_material(&self) -> KeyMaterial;
 }
 
 #[derive(Clone)]
@@ -419,6 +485,8 @@ pub struct InMemorySigner {
        pub commitment_seed: [u8; 32],
        /// Holder public keys and basepoints
        pub(crate) holder_channel_pubkeys: ChannelPublicKeys,
+       /// Private key of our node secret, used for signing channel announcements
+       node_secret: SecretKey,
        /// Counterparty public keys and counterparty/holder selected_contest_delay, populated on channel acceptance
        channel_parameters: Option<ChannelTransactionParameters>,
        /// The total value of this channel
@@ -431,6 +499,7 @@ impl InMemorySigner {
        /// Create a new InMemorySigner
        pub fn new<C: Signing>(
                secp_ctx: &Secp256k1<C>,
+               node_secret: SecretKey,
                funding_key: SecretKey,
                revocation_base_key: SecretKey,
                payment_key: SecretKey,
@@ -450,6 +519,7 @@ impl InMemorySigner {
                        delayed_payment_base_key,
                        htlc_base_key,
                        commitment_seed,
+                       node_secret,
                        channel_value_satoshis,
                        holder_channel_pubkeys,
                        channel_parameters: None,
@@ -515,7 +585,8 @@ impl InMemorySigner {
        /// described by descriptor, returning the witness stack for the input.
        ///
        /// Returns an Err if the input at input_idx does not exist, has a non-empty script_sig,
-       /// or is not spending the outpoint described by `descriptor.outpoint`.
+       /// is not spending the outpoint described by `descriptor.outpoint`,
+       /// or if an output descriptor script_pubkey does not match the one we can spend.
        pub fn sign_counterparty_payment_input<C: Signing>(&self, spend_tx: &Transaction, input_idx: usize, descriptor: &StaticPaymentOutputDescriptor, secp_ctx: &Secp256k1<C>) -> Result<Vec<Vec<u8>>, ()> {
                // TODO: We really should be taking the SigHashCache as a parameter here instead of
                // spend_tx, but ideally the SigHashCache would expose the transaction's inputs read-only
@@ -526,13 +597,16 @@ impl InMemorySigner {
                if spend_tx.input[input_idx].previous_output != descriptor.outpoint.into_bitcoin_outpoint() { return Err(()); }
 
                let remotepubkey = self.pubkeys().payment_point;
-               let witness_script = bitcoin::Address::p2pkh(&::bitcoin::PublicKey{compressed: true, key: remotepubkey}, Network::Testnet).script_pubkey();
-               let sighash = hash_to_message!(&bip143::SigHashCache::new(spend_tx).signature_hash(input_idx, &witness_script, descriptor.output.value, SigHashType::All)[..]);
-               let remotesig = secp_ctx.sign(&sighash, &self.payment_key);
+               let witness_script = bitcoin::Address::p2pkh(&::bitcoin::PublicKey{compressed: true, inner: remotepubkey}, Network::Testnet).script_pubkey();
+               let sighash = hash_to_message!(&sighash::SighashCache::new(spend_tx).segwit_signature_hash(input_idx, &witness_script, descriptor.output.value, EcdsaSighashType::All).unwrap()[..]);
+               let remotesig = sign(secp_ctx, &sighash, &self.payment_key);
+               let payment_script = bitcoin::Address::p2wpkh(&::bitcoin::PublicKey{compressed: true, inner: remotepubkey}, Network::Bitcoin).unwrap().script_pubkey();
+
+               if payment_script != descriptor.output.script_pubkey  { return Err(()); }
 
                let mut witness = Vec::with_capacity(2);
                witness.push(remotesig.serialize_der().to_vec());
-               witness[0].push(SigHashType::All as u8);
+               witness[0].push(EcdsaSighashType::All as u8);
                witness.push(remotepubkey.serialize().to_vec());
                Ok(witness)
        }
@@ -541,8 +615,9 @@ impl InMemorySigner {
        /// described by descriptor, returning the witness stack for the input.
        ///
        /// Returns an Err if the input at input_idx does not exist, has a non-empty script_sig,
-       /// is not spending the outpoint described by `descriptor.outpoint`, or does not have a
-       /// sequence set to `descriptor.to_self_delay`.
+       /// is not spending the outpoint described by `descriptor.outpoint`, does not have a
+       /// sequence set to `descriptor.to_self_delay`, or if an output descriptor
+       /// script_pubkey does not match the one we can spend.
        pub fn sign_dynamic_p2wsh_input<C: Signing>(&self, spend_tx: &Transaction, input_idx: usize, descriptor: &DelayedPaymentOutputDescriptor, secp_ctx: &Secp256k1<C>) -> Result<Vec<Vec<u8>>, ()> {
                // TODO: We really should be taking the SigHashCache as a parameter here instead of
                // spend_tx, but ideally the SigHashCache would expose the transaction's inputs read-only
@@ -551,18 +626,21 @@ impl InMemorySigner {
                if spend_tx.input.len() <= input_idx { return Err(()); }
                if !spend_tx.input[input_idx].script_sig.is_empty() { return Err(()); }
                if spend_tx.input[input_idx].previous_output != descriptor.outpoint.into_bitcoin_outpoint() { return Err(()); }
-               if spend_tx.input[input_idx].sequence != descriptor.to_self_delay as u32 { return Err(()); }
+               if spend_tx.input[input_idx].sequence.0 != descriptor.to_self_delay as u32 { return Err(()); }
 
                let delayed_payment_key = chan_utils::derive_private_key(&secp_ctx, &descriptor.per_commitment_point, &self.delayed_payment_base_key)
                        .expect("We constructed the payment_base_key, so we can only fail here if the RNG is busted.");
                let delayed_payment_pubkey = PublicKey::from_secret_key(&secp_ctx, &delayed_payment_key);
                let witness_script = chan_utils::get_revokeable_redeemscript(&descriptor.revocation_pubkey, descriptor.to_self_delay, &delayed_payment_pubkey);
-               let sighash = hash_to_message!(&bip143::SigHashCache::new(spend_tx).signature_hash(input_idx, &witness_script, descriptor.output.value, SigHashType::All)[..]);
-               let local_delayedsig = secp_ctx.sign(&sighash, &delayed_payment_key);
+               let sighash = hash_to_message!(&sighash::SighashCache::new(spend_tx).segwit_signature_hash(input_idx, &witness_script, descriptor.output.value, EcdsaSighashType::All).unwrap()[..]);
+               let local_delayedsig = sign(secp_ctx, &sighash, &delayed_payment_key);
+               let payment_script = bitcoin::Address::p2wsh(&witness_script, Network::Bitcoin).script_pubkey();
+
+               if descriptor.output.script_pubkey != payment_script { return Err(()); }
 
                let mut witness = Vec::with_capacity(3);
                witness.push(local_delayedsig.serialize_der().to_vec());
-               witness[0].push(SigHashType::All as u8);
+               witness[0].push(EcdsaSighashType::All as u8);
                witness.push(vec!()); //MINIMALIF
                witness.push(witness_script.clone().into_bytes());
                Ok(witness)
@@ -579,14 +657,14 @@ impl BaseSign for InMemorySigner {
                chan_utils::build_commitment_secret(&self.commitment_seed, idx)
        }
 
-       fn validate_holder_commitment(&self, _holder_tx: &HolderCommitmentTransaction) -> Result<(), ()> {
+       fn validate_holder_commitment(&self, _holder_tx: &HolderCommitmentTransaction, _preimages: Vec<PaymentPreimage>) -> Result<(), ()> {
                Ok(())
        }
 
        fn pubkeys(&self) -> &ChannelPublicKeys { &self.holder_channel_pubkeys }
        fn channel_keys_id(&self) -> [u8; 32] { self.channel_keys_id }
 
-       fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
+       fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, _preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
                let trusted_tx = commitment_tx.trust();
                let keys = trusted_tx.keys();
 
@@ -601,9 +679,10 @@ impl BaseSign for InMemorySigner {
                for htlc in commitment_tx.htlcs() {
                        let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, commitment_tx.feerate_per_kw(), self.holder_selected_contest_delay(), htlc, self.opt_anchors(), &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
                        let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, self.opt_anchors(), &keys);
-                       let htlc_sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, htlc.amount_msat / 1000, SigHashType::All)[..]);
+                       let htlc_sighashtype = if self.opt_anchors() { EcdsaSighashType::SinglePlusAnyoneCanPay } else { EcdsaSighashType::All };
+                       let htlc_sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(0, &htlc_redeemscript, htlc.amount_msat / 1000, htlc_sighashtype).unwrap()[..]);
                        let holder_htlc_key = chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key).map_err(|_| ())?;
-                       htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &holder_htlc_key));
+                       htlc_sigs.push(sign(secp_ctx, &htlc_sighash, &holder_htlc_key));
                }
 
                Ok((commitment_sig, htlc_sigs))
@@ -642,9 +721,9 @@ impl BaseSign for InMemorySigner {
                        let counterparty_delayedpubkey = chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.counterparty_pubkeys().delayed_payment_basepoint).map_err(|_| ())?;
                        chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.holder_selected_contest_delay(), &counterparty_delayedpubkey)
                };
-               let mut sighash_parts = bip143::SigHashCache::new(justice_tx);
-               let sighash = hash_to_message!(&sighash_parts.signature_hash(input, &witness_script, amount, SigHashType::All)[..]);
-               return Ok(secp_ctx.sign(&sighash, &revocation_key))
+               let mut sighash_parts = sighash::SighashCache::new(justice_tx);
+               let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]);
+               return Ok(sign(secp_ctx, &sighash, &revocation_key))
        }
 
        fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
@@ -656,9 +735,9 @@ impl BaseSign for InMemorySigner {
                        let holder_htlcpubkey = chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.pubkeys().htlc_basepoint).map_err(|_| ())?;
                        chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, self.opt_anchors(), &counterparty_htlcpubkey, &holder_htlcpubkey, &revocation_pubkey)
                };
-               let mut sighash_parts = bip143::SigHashCache::new(justice_tx);
-               let sighash = hash_to_message!(&sighash_parts.signature_hash(input, &witness_script, amount, SigHashType::All)[..]);
-               return Ok(secp_ctx.sign(&sighash, &revocation_key))
+               let mut sighash_parts = sighash::SighashCache::new(justice_tx);
+               let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]);
+               return Ok(sign(secp_ctx, &sighash, &revocation_key))
        }
 
        fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
@@ -670,9 +749,9 @@ impl BaseSign for InMemorySigner {
                                        } else { return Err(()) }
                                } else { return Err(()) }
                        } else { return Err(()) };
-                       let mut sighash_parts = bip143::SigHashCache::new(htlc_tx);
-                       let sighash = hash_to_message!(&sighash_parts.signature_hash(input, &witness_script, amount, SigHashType::All)[..]);
-                       return Ok(secp_ctx.sign(&sighash, &htlc_key))
+                       let mut sighash_parts = sighash::SighashCache::new(htlc_tx);
+                       let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]);
+                       return Ok(sign(secp_ctx, &sighash, &htlc_key))
                }
                Err(())
        }
@@ -683,9 +762,10 @@ impl BaseSign for InMemorySigner {
                Ok(closing_tx.trust().sign(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
        }
 
-       fn sign_channel_announcement(&self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
+       fn sign_channel_announcement(&self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>)
+       -> Result<(Signature, Signature), ()> {
                let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
-               Ok(secp_ctx.sign(&msghash, &self.funding_key))
+               Ok((sign(secp_ctx, &msghash, &self.node_secret), sign(secp_ctx, &msghash, &self.funding_key)))
        }
 
        fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
@@ -720,8 +800,8 @@ impl Writeable for InMemorySigner {
        }
 }
 
-impl Readable for InMemorySigner {
-       fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+impl ReadableArgs<SecretKey> for InMemorySigner {
+       fn read<R: io::Read>(reader: &mut R, node_secret: SecretKey) -> Result<Self, DecodeError> {
                let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);
 
                let funding_key = Readable::read(reader)?;
@@ -747,6 +827,7 @@ impl Readable for InMemorySigner {
                        payment_key,
                        delayed_payment_base_key,
                        htlc_base_key,
+                       node_secret,
                        commitment_seed,
                        channel_value_satoshis,
                        holder_channel_pubkeys,
@@ -763,9 +844,16 @@ impl Readable for InMemorySigner {
 /// ChannelMonitor closes may use seed/1'
 /// Cooperative closes may use seed/2'
 /// The two close keys may be needed to claim on-chain funds!
+///
+/// This struct cannot be used for nodes that wish to support receiving phantom payments;
+/// [`PhantomKeysManager`] must be used instead.
+///
+/// Note that switching between this struct and [`PhantomKeysManager`] will invalidate any
+/// previously issued invoices and attempts to pay previous invoices will fail.
 pub struct KeysManager {
        secp_ctx: Secp256k1<secp256k1::All>,
        node_secret: SecretKey,
+       inbound_payment_key: KeyMaterial,
        destination_script: Script,
        shutdown_pubkey: PublicKey,
        channel_master_key: ExtendedPrivKey,
@@ -805,10 +893,10 @@ impl KeysManager {
                // Note that when we aren't serializing the key, network doesn't matter
                match ExtendedPrivKey::new_master(Network::Testnet, seed) {
                        Ok(master_key) => {
-                               let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key.key;
+                               let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key;
                                let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1).unwrap()) {
                                        Ok(destination_key) => {
-                                               let wpubkey_hash = WPubkeyHash::hash(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.to_bytes());
+                                               let wpubkey_hash = WPubkeyHash::hash(&ExtendedPubKey::from_priv(&secp_ctx, &destination_key).to_pub().to_bytes());
                                                Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
                                                              .push_slice(&wpubkey_hash.into_inner())
                                                              .into_script()
@@ -816,11 +904,14 @@ impl KeysManager {
                                        Err(_) => panic!("Your RNG is busted"),
                                };
                                let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2).unwrap()) {
-                                       Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key.key,
+                                       Ok(shutdown_key) => ExtendedPubKey::from_priv(&secp_ctx, &shutdown_key).public_key,
                                        Err(_) => panic!("Your RNG is busted"),
                                };
                                let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3).unwrap()).expect("Your RNG is busted");
                                let rand_bytes_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4).unwrap()).expect("Your RNG is busted");
+                               let inbound_payment_key: SecretKey = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(5).unwrap()).expect("Your RNG is busted").private_key;
+                               let mut inbound_pmt_key_bytes = [0; 32];
+                               inbound_pmt_key_bytes.copy_from_slice(&inbound_payment_key[..]);
 
                                let mut rand_bytes_unique_start = Sha256::engine();
                                rand_bytes_unique_start.input(&byte_utils::be64_to_array(starting_time_secs));
@@ -830,6 +921,7 @@ impl KeysManager {
                                let mut res = KeysManager {
                                        secp_ctx,
                                        node_secret,
+                                       inbound_payment_key: KeyMaterial(inbound_pmt_key_bytes),
 
                                        destination_script,
                                        shutdown_pubkey,
@@ -868,7 +960,7 @@ impl KeysManager {
                // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
                // starting_time provided in the constructor) to be unique.
                let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(chan_id as u32).expect("key space exhausted")).expect("Your RNG is busted");
-               unique_start.input(&child_privkey.private_key.key[..]);
+               unique_start.input(&child_privkey.private_key[..]);
 
                let seed = Sha256::from_engine(unique_start).into_inner();
 
@@ -895,6 +987,7 @@ impl KeysManager {
 
                InMemorySigner::new(
                        &self.secp_ctx,
+                       self.node_secret,
                        funding_key,
                        revocation_base_key,
                        payment_key,
@@ -910,8 +1003,9 @@ impl KeysManager {
        /// output to the given change destination (if sufficient change value remains). The
        /// transaction will have a feerate, at least, of the given value.
        ///
-       /// Returns `Err(())` if the output value is greater than the input value minus required fee or
-       /// if a descriptor was duplicated.
+       /// Returns `Err(())` if the output value is greater than the input value minus required fee,
+       /// if a descriptor was duplicated, or if an output descriptor `script_pubkey`
+       /// does not match the one we can spend.
        ///
        /// We do not enforce that outputs meet the dust limit or that any output scripts are standard.
        ///
@@ -928,8 +1022,8 @@ impl KeysManager {
                                        input.push(TxIn {
                                                previous_output: descriptor.outpoint.into_bitcoin_outpoint(),
                                                script_sig: Script::new(),
-                                               sequence: 0,
-                                               witness: Vec::new(),
+                                               sequence: Sequence::ZERO,
+                                               witness: Witness::new(),
                                        });
                                        witness_weight += StaticPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
                                        input_value += descriptor.output.value;
@@ -939,8 +1033,8 @@ impl KeysManager {
                                        input.push(TxIn {
                                                previous_output: descriptor.outpoint.into_bitcoin_outpoint(),
                                                script_sig: Script::new(),
-                                               sequence: descriptor.to_self_delay as u32,
-                                               witness: Vec::new(),
+                                               sequence: Sequence(descriptor.to_self_delay as u32),
+                                               witness: Witness::new(),
                                        });
                                        witness_weight += DelayedPaymentOutputDescriptor::MAX_WITNESS_LENGTH;
                                        input_value += descriptor.output.value;
@@ -950,8 +1044,8 @@ impl KeysManager {
                                        input.push(TxIn {
                                                previous_output: outpoint.into_bitcoin_outpoint(),
                                                script_sig: Script::new(),
-                                               sequence: 0,
-                                               witness: Vec::new(),
+                                               sequence: Sequence::ZERO,
+                                               witness: Witness::new(),
                                        });
                                        witness_weight += 1 + 73 + 34;
                                        input_value += output.value;
@@ -962,7 +1056,7 @@ impl KeysManager {
                }
                let mut spend_tx = Transaction {
                        version: 2,
-                       lock_time: 0,
+                       lock_time: PackedLockTime(0),
                        input,
                        output: outputs,
                };
@@ -979,7 +1073,7 @@ impl KeysManager {
                                                        self.derive_channel_keys(descriptor.channel_value_satoshis, &descriptor.channel_keys_id),
                                                        descriptor.channel_keys_id));
                                        }
-                                       spend_tx.input[input_idx].witness = keys_cache.as_ref().unwrap().0.sign_counterparty_payment_input(&spend_tx, input_idx, &descriptor, &secp_ctx).unwrap();
+                                       spend_tx.input[input_idx].witness = Witness::from_vec(keys_cache.as_ref().unwrap().0.sign_counterparty_payment_input(&spend_tx, input_idx, &descriptor, &secp_ctx)?);
                                },
                                SpendableOutputDescriptor::DelayedPaymentOutput(descriptor) => {
                                        if keys_cache.is_none() || keys_cache.as_ref().unwrap().1 != descriptor.channel_keys_id {
@@ -987,7 +1081,7 @@ impl KeysManager {
                                                        self.derive_channel_keys(descriptor.channel_value_satoshis, &descriptor.channel_keys_id),
                                                        descriptor.channel_keys_id));
                                        }
-                                       spend_tx.input[input_idx].witness = keys_cache.as_ref().unwrap().0.sign_dynamic_p2wsh_input(&spend_tx, input_idx, &descriptor, &secp_ctx).unwrap();
+                                       spend_tx.input[input_idx].witness = Witness::from_vec(keys_cache.as_ref().unwrap().0.sign_dynamic_p2wsh_input(&spend_tx, input_idx, &descriptor, &secp_ctx)?);
                                },
                                SpendableOutputDescriptor::StaticOutput { ref output, .. } => {
                                        let derivation_idx = if output.script_pubkey == self.destination_script {
@@ -1007,25 +1101,30 @@ impl KeysManager {
                                                        Err(_) => panic!("Your rng is busted"),
                                                }
                                        };
-                                       let pubkey = ExtendedPubKey::from_private(&secp_ctx, &secret).public_key;
+                                       let pubkey = ExtendedPubKey::from_priv(&secp_ctx, &secret).to_pub();
                                        if derivation_idx == 2 {
-                                               assert_eq!(pubkey.key, self.shutdown_pubkey);
+                                               assert_eq!(pubkey.inner, self.shutdown_pubkey);
                                        }
                                        let witness_script = bitcoin::Address::p2pkh(&pubkey, Network::Testnet).script_pubkey();
-                                       let sighash = hash_to_message!(&bip143::SigHashCache::new(&spend_tx).signature_hash(input_idx, &witness_script, output.value, SigHashType::All)[..]);
-                                       let sig = secp_ctx.sign(&sighash, &secret.private_key.key);
-                                       spend_tx.input[input_idx].witness.push(sig.serialize_der().to_vec());
-                                       spend_tx.input[input_idx].witness[0].push(SigHashType::All as u8);
-                                       spend_tx.input[input_idx].witness.push(pubkey.key.serialize().to_vec());
+                                       let payment_script = bitcoin::Address::p2wpkh(&pubkey, Network::Testnet).expect("uncompressed key found").script_pubkey();
+
+                                       if payment_script != output.script_pubkey { return Err(()); };
+
+                                       let sighash = hash_to_message!(&sighash::SighashCache::new(&spend_tx).segwit_signature_hash(input_idx, &witness_script, output.value, EcdsaSighashType::All).unwrap()[..]);
+                                       let sig = sign(secp_ctx, &sighash, &secret.private_key);
+                                       let mut sig_ser = sig.serialize_der().to_vec();
+                                       sig_ser.push(EcdsaSighashType::All as u8);
+                                       spend_tx.input[input_idx].witness.push(sig_ser);
+                                       spend_tx.input[input_idx].witness.push(pubkey.inner.serialize().to_vec());
                                },
                        }
                        input_idx += 1;
                }
 
-               debug_assert!(expected_max_weight >= spend_tx.get_weight());
+               debug_assert!(expected_max_weight >= spend_tx.weight());
                // Note that witnesses with a signature vary somewhat in size, so allow
                // `expected_max_weight` to overshoot by up to 3 bytes per input.
-               debug_assert!(expected_max_weight <= spend_tx.get_weight() + descriptors.len() * 3);
+               debug_assert!(expected_max_weight <= spend_tx.weight() + descriptors.len() * 3);
 
                Ok(spend_tx)
        }
@@ -1034,8 +1133,23 @@ impl KeysManager {
 impl KeysInterface for KeysManager {
        type Signer = InMemorySigner;
 
-       fn get_node_secret(&self) -> SecretKey {
-               self.node_secret.clone()
+       fn get_node_secret(&self, recipient: Recipient) -> Result<SecretKey, ()> {
+               match recipient {
+                       Recipient::Node => Ok(self.node_secret.clone()),
+                       Recipient::PhantomNode => Err(())
+               }
+       }
+
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&Scalar>) -> Result<SharedSecret, ()> {
+               let mut node_secret = self.get_node_secret(recipient)?;
+               if let Some(tweak) = tweak {
+                       node_secret = node_secret.mul_tweak(tweak).map_err(|_| ())?;
+               }
+               Ok(SharedSecret::new(other_key, &node_secret))
+       }
+
+       fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+               self.inbound_payment_key.clone()
        }
 
        fn get_destination_script(&self) -> Script {
@@ -1061,18 +1175,131 @@ impl KeysInterface for KeysManager {
 
                let child_ix = self.rand_bytes_child_index.fetch_add(1, Ordering::AcqRel);
                let child_privkey = self.rand_bytes_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
-               sha.input(&child_privkey.private_key.key[..]);
+               sha.input(&child_privkey.private_key[..]);
 
                sha.input(b"Unique Secure Random Bytes Salt");
                Sha256::from_engine(sha).into_inner()
        }
 
        fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, DecodeError> {
-               InMemorySigner::read(&mut io::Cursor::new(reader))
+               InMemorySigner::read(&mut io::Cursor::new(reader), self.node_secret.clone())
+       }
+
+       fn sign_invoice(&self, hrp_bytes: &[u8], invoice_data: &[u5], recipient: Recipient) -> Result<RecoverableSignature, ()> {
+               let preimage = construct_invoice_preimage(&hrp_bytes, &invoice_data);
+               let secret = match recipient {
+                       Recipient::Node => self.get_node_secret(Recipient::Node)?,
+                       Recipient::PhantomNode => return Err(()),
+               };
+               Ok(self.secp_ctx.sign_ecdsa_recoverable(&hash_to_message!(&Sha256::hash(&preimage)), &secret))
+       }
+}
+
+/// Similar to [`KeysManager`], but allows the node using this struct to receive phantom node
+/// payments.
+///
+/// A phantom node payment is a payment made to a phantom invoice, which is an invoice that can be
+/// paid to one of multiple nodes. This works because we encode the invoice route hints such that
+/// LDK will recognize an incoming payment as destined for a phantom node, and collect the payment
+/// itself without ever needing to forward to this fake node.
+///
+/// Phantom node payments are useful for load balancing between multiple LDK nodes. They also
+/// provide some fault tolerance, because payers will automatically retry paying other provided
+/// nodes in the case that one node goes down.
+///
+/// Note that multi-path payments are not supported in phantom invoices for security reasons.
+//  In the hypothetical case that we did support MPP phantom payments, there would be no way for
+//  nodes to know when the full payment has been received (and the preimage can be released) without
+//  significantly compromising on our safety guarantees. I.e., if we expose the ability for the user
+//  to tell LDK when the preimage can be released, we open ourselves to attacks where the preimage
+//  is released too early.
+//
+/// Switching between this struct and [`KeysManager`] will invalidate any previously issued
+/// invoices and attempts to pay previous invoices will fail.
+pub struct PhantomKeysManager {
+       inner: KeysManager,
+       inbound_payment_key: KeyMaterial,
+       phantom_secret: SecretKey,
+}
+
+impl KeysInterface for PhantomKeysManager {
+       type Signer = InMemorySigner;
+
+       fn get_node_secret(&self, recipient: Recipient) -> Result<SecretKey, ()> {
+               match recipient {
+                       Recipient::Node => self.inner.get_node_secret(Recipient::Node),
+                       Recipient::PhantomNode => Ok(self.phantom_secret.clone()),
+               }
+       }
+
+       fn ecdh(&self, recipient: Recipient, other_key: &PublicKey, tweak: Option<&Scalar>) -> Result<SharedSecret, ()> {
+               let mut node_secret = self.get_node_secret(recipient)?;
+               if let Some(tweak) = tweak {
+                       node_secret = node_secret.mul_tweak(tweak).map_err(|_| ())?;
+               }
+               Ok(SharedSecret::new(other_key, &node_secret))
+       }
+
+       fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+               self.inbound_payment_key.clone()
+       }
+
+       fn get_destination_script(&self) -> Script {
+               self.inner.get_destination_script()
+       }
+
+       fn get_shutdown_scriptpubkey(&self) -> ShutdownScript {
+               self.inner.get_shutdown_scriptpubkey()
+       }
+
+       fn get_channel_signer(&self, inbound: bool, channel_value_satoshis: u64) -> Self::Signer {
+               self.inner.get_channel_signer(inbound, channel_value_satoshis)
+       }
+
+       fn get_secure_random_bytes(&self) -> [u8; 32] {
+               self.inner.get_secure_random_bytes()
+       }
+
+       fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, DecodeError> {
+               self.inner.read_chan_signer(reader)
        }
 
-       fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
-               Ok(self.secp_ctx.sign_recoverable(&hash_to_message!(&Sha256::hash(&invoice_preimage)), &self.get_node_secret()))
+       fn sign_invoice(&self, hrp_bytes: &[u8], invoice_data: &[u5], recipient: Recipient) -> Result<RecoverableSignature, ()> {
+               let preimage = construct_invoice_preimage(&hrp_bytes, &invoice_data);
+               let secret = self.get_node_secret(recipient)?;
+               Ok(self.inner.secp_ctx.sign_ecdsa_recoverable(&hash_to_message!(&Sha256::hash(&preimage)), &secret))
+       }
+}
+
+impl PhantomKeysManager {
+       /// Constructs a `PhantomKeysManager` given a 32-byte seed and an additional `cross_node_seed`
+       /// that is shared across all nodes that intend to participate in [phantom node payments] together.
+       ///
+       /// See [`KeysManager::new`] for more information on `seed`, `starting_time_secs`, and
+       /// `starting_time_nanos`.
+       ///
+       /// `cross_node_seed` must be the same across all phantom payment-receiving nodes and also the
+       /// same across restarts, or else inbound payments may fail.
+       ///
+       /// [phantom node payments]: PhantomKeysManager
+       pub fn new(seed: &[u8; 32], starting_time_secs: u64, starting_time_nanos: u32, cross_node_seed: &[u8; 32]) -> Self {
+               let inner = KeysManager::new(seed, starting_time_secs, starting_time_nanos);
+               let (inbound_key, phantom_key) = hkdf_extract_expand_twice(b"LDK Inbound and Phantom Payment Key Expansion", cross_node_seed);
+               Self {
+                       inner,
+                       inbound_payment_key: KeyMaterial(inbound_key),
+                       phantom_secret: SecretKey::from_slice(&phantom_key).unwrap(),
+               }
+       }
+
+       /// See [`KeysManager::spend_spendable_outputs`] for documentation on this method.
+       pub fn spend_spendable_outputs<C: Signing>(&self, descriptors: &[&SpendableOutputDescriptor], outputs: Vec<TxOut>, change_destination_script: Script, feerate_sat_per_1000_weight: u32, secp_ctx: &Secp256k1<C>) -> Result<Transaction, ()> {
+               self.inner.spend_spendable_outputs(descriptors, outputs, change_destination_script, feerate_sat_per_1000_weight, secp_ctx)
+       }
+
+       /// See [`KeysManager::derive_channel_keys`] for documentation on this method.
+       pub fn derive_channel_keys(&self, channel_value_satoshis: u64, params: &[u8; 32]) -> InMemorySigner {
+               self.inner.derive_channel_keys(channel_value_satoshis, params)
        }
 }