1 //! keysinterface provides keys into rust-lightning and defines some useful enums which describe
2 //! spendable on-chain outputs which the user owns and is responsible for using just as any other
3 //! on-chain output which is theirs.
5 use bitcoin::blockdata::transaction::{Transaction, OutPoint, TxOut};
6 use bitcoin::blockdata::script::{Script, Builder};
7 use bitcoin::blockdata::opcodes;
8 use bitcoin::network::constants::Network;
9 use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber};
10 use bitcoin::util::bip143;
12 use bitcoin_hashes::{Hash, HashEngine};
13 use bitcoin_hashes::sha256::HashEngine as Sha256State;
14 use bitcoin_hashes::sha256::Hash as Sha256;
15 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
16 use bitcoin_hashes::hash160::Hash as Hash160;
18 use secp256k1::key::{SecretKey, PublicKey};
19 use secp256k1::{Secp256k1, Signature, Signing};
23 use util::logger::Logger;
24 use util::ser::{Writeable, Writer, Readable};
27 use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys};
31 use std::sync::atomic::{AtomicUsize, Ordering};
33 use ln::msgs::DecodeError;
35 /// When on-chain outputs are created by rust-lightning (which our counterparty is not able to
36 /// claim at any point in the future) an event is generated which you must track and be able to
37 /// spend on-chain. The information needed to do this is provided in this enum, including the
38 /// outpoint describing which txid and output index is available, the full output which exists at
39 /// that txid/index, and any keys or other information required to sign.
40 pub enum SpendableOutputDescriptor {
41 /// An output to a script which was provided via KeysInterface, thus you should already know
42 /// how to spend it. No keys are provided as rust-lightning was never given any keys - only the
43 /// script_pubkey as it appears in the output.
44 /// These may include outputs from a transaction punishing our counterparty or claiming an HTLC
45 /// on-chain using the payment preimage or after it has timed out.
47 /// The outpoint which is spendable
49 /// The output which is referenced by the given outpoint.
52 /// An output to a P2WSH script which can be spent with a single signature after a CSV delay.
53 /// The private key which should be used to sign the transaction is provided, as well as the
54 /// full witness redeemScript which is hashed in the output script_pubkey.
55 /// The witness in the spending input should be:
56 /// <BIP 143 signature generated with the given key> <one zero byte aka OP_0>
57 /// <witness_script as provided>
58 /// Note that the nSequence field in the input must be set to_self_delay (which corresponds to
59 /// the transaction not being broadcastable until at least to_self_delay blocks after the input
61 /// These are generally the result of a "revocable" output to us, spendable only by us unless
62 /// it is an output from us having broadcast an old state (which should never happen).
64 /// The outpoint which is spendable
66 /// The secret key which must be used to sign the spending transaction
68 /// The witness redeemScript which is hashed to create the script_pubkey in the given output
69 witness_script: Script,
70 /// The nSequence value which must be set in the spending input to satisfy the OP_CSV in
71 /// the witness_script.
73 /// The output which is referenced by the given outpoint
76 /// An output to a P2WPKH, spendable exclusively by the given private key.
77 /// The witness in the spending input, is, thus, simply:
78 /// <BIP 143 signature generated with the given key> <public key derived from the given key>
79 /// These are generally the result of our counterparty having broadcast the current state,
80 /// allowing us to claim the non-HTLC-encumbered outputs immediately.
82 /// The outpoint which is spendable
84 /// The secret key which must be used to sign the spending transaction
86 /// The output which is reference by the given outpoint
91 /// A trait to describe an object which can get user secrets and key material.
92 pub trait KeysInterface: Send + Sync {
93 /// A type which implements ChannelKeys which will be returned by get_channel_keys.
94 type ChanKeySigner : ChannelKeys;
96 /// Get node secret key (aka node_id or network_key)
97 fn get_node_secret(&self) -> SecretKey;
98 /// Get destination redeemScript to encumber static protocol exit points.
99 fn get_destination_script(&self) -> Script;
100 /// Get shutdown_pubkey to use as PublicKey at channel closure
101 fn get_shutdown_pubkey(&self) -> PublicKey;
102 /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you
103 /// restarted with some stale data!
104 fn get_channel_keys(&self, inbound: bool, channel_value_satoshis: u64) -> Self::ChanKeySigner;
105 /// Get a secret and PRNG seed for construting an onion packet
106 fn get_onion_rand(&self) -> (SecretKey, [u8; 32]);
107 /// Get a unique temporary channel id. Channels will be referred to by this until the funding
108 /// transaction is created, at which point they will use the outpoint in the funding
110 fn get_channel_id(&self) -> [u8; 32];
113 /// Set of lightning keys needed to operate a channel as described in BOLT 3.
115 /// Signing services could be implemented on a hardware wallet. In this case,
116 /// the current ChannelKeys would be a front-end on top of a communication
117 /// channel connected to your secure device and lightning key material wouldn't
118 /// reside on a hot server. Nevertheless, a this deployment would still need
119 /// to trust the ChannelManager to avoid loss of funds as this latest component
120 /// could ask to sign commitment transaction with HTLCs paying to attacker pubkeys.
122 /// A more secure iteration would be to use hashlock (or payment points) to pair
123 /// invoice/incoming HTLCs with outgoing HTLCs to implement a no-trust-ChannelManager
124 /// at the price of more state and computation on the hardware wallet side. In the future,
125 /// we are looking forward to design such interface.
127 /// In any case, ChannelMonitor or fallback watchtowers are always going to be trusted
128 /// to act, as liveness and breach reply correctness are always going to be hard requirements
129 /// of LN security model, orthogonal of key management issues.
131 /// If you're implementing a custom signer, you almost certainly want to implement
132 /// Readable/Writable to serialize out a unique reference to this set of keys so
133 /// that you can serialize the full ChannelManager object.
135 /// (TODO: We shouldn't require that, and should have an API to get them at deser time, due mostly
136 /// to the possibility of reentrancy issues by calling the user's code during our deserialization
138 /// TODO: We should remove Clone by instead requesting a new ChannelKeys copy when we create
139 /// ChannelMonitors instead of expecting to clone the one out of the Channel into the monitors.
140 pub trait ChannelKeys : Send+Clone {
141 /// Gets the private key for the anchor tx
142 fn funding_key<'a>(&'a self) -> &'a SecretKey;
143 /// Gets the local secret key for blinded revocation pubkey
144 fn revocation_base_key<'a>(&'a self) -> &'a SecretKey;
145 /// Gets the local secret key used in to_remote output of remote commitment tx
146 /// (and also as part of obscured commitment number)
147 fn payment_base_key<'a>(&'a self) -> &'a SecretKey;
148 /// Gets the local secret key used in HTLC-Success/HTLC-Timeout txn and to_local output
149 fn delayed_payment_base_key<'a>(&'a self) -> &'a SecretKey;
150 /// Gets the local htlc secret key used in commitment tx htlc outputs
151 fn htlc_base_key<'a>(&'a self) -> &'a SecretKey;
152 /// Gets the commitment seed
153 fn commitment_seed<'a>(&'a self) -> &'a [u8; 32];
154 /// Gets the local channel public keys and basepoints
155 fn pubkeys<'a>(&'a self) -> &'a ChannelPublicKeys;
157 /// Create a signature for a remote commitment transaction and associated HTLC transactions.
159 /// Note that if signing fails or is rejected, the channel will be force-closed.
161 /// TODO: Document the things someone using this interface should enforce before signing.
162 /// TODO: Add more input vars to enable better checking (preferably removing commitment_tx and
163 /// making the callee generate it via some util function we expose)!
164 fn sign_remote_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()>;
166 /// Create a signature for a (proposed) closing transaction.
168 /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
169 /// chosen to forgo their output as dust.
170 fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
172 /// Signs a channel announcement message with our funding key, proving it comes from one
173 /// of the channel participants.
175 /// Note that if this fails or is rejected, the channel will not be publicly announced and
176 /// our counterparty may (though likely will not) close the channel on us for violating the
178 fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
180 /// Set the remote channel basepoints. This is done immediately on incoming channels
181 /// and as soon as the channel is accepted on outgoing channels.
183 /// Will be called before any signatures are applied.
184 fn set_remote_channel_pubkeys(&mut self, channel_points: &ChannelPublicKeys);
188 /// A simple implementation of ChannelKeys that just keeps the private keys in memory.
189 pub struct InMemoryChannelKeys {
190 /// Private key of anchor tx
191 funding_key: SecretKey,
192 /// Local secret key for blinded revocation pubkey
193 revocation_base_key: SecretKey,
194 /// Local secret key used in commitment tx htlc outputs
195 payment_base_key: SecretKey,
196 /// Local secret key used in HTLC tx
197 delayed_payment_base_key: SecretKey,
198 /// Local htlc secret key used in commitment tx htlc outputs
199 htlc_base_key: SecretKey,
201 commitment_seed: [u8; 32],
202 /// Local public keys and basepoints
203 pub(crate) local_channel_pubkeys: ChannelPublicKeys,
204 /// Remote public keys and base points
205 pub(crate) remote_channel_pubkeys: Option<ChannelPublicKeys>,
206 /// The total value of this channel
207 channel_value_satoshis: u64,
210 impl InMemoryChannelKeys {
211 /// Create a new InMemoryChannelKeys
212 pub fn new<C: Signing>(
213 secp_ctx: &Secp256k1<C>,
214 funding_key: SecretKey,
215 revocation_base_key: SecretKey,
216 payment_base_key: SecretKey,
217 delayed_payment_base_key: SecretKey,
218 htlc_base_key: SecretKey,
219 commitment_seed: [u8; 32],
220 channel_value_satoshis: u64) -> InMemoryChannelKeys {
221 let local_channel_pubkeys =
222 InMemoryChannelKeys::make_local_keys(secp_ctx, &funding_key, &revocation_base_key,
223 &payment_base_key, &delayed_payment_base_key,
225 InMemoryChannelKeys {
229 delayed_payment_base_key,
232 channel_value_satoshis,
233 local_channel_pubkeys,
234 remote_channel_pubkeys: None,
238 fn make_local_keys<C: Signing>(secp_ctx: &Secp256k1<C>,
239 funding_key: &SecretKey,
240 revocation_base_key: &SecretKey,
241 payment_base_key: &SecretKey,
242 delayed_payment_base_key: &SecretKey,
243 htlc_base_key: &SecretKey) -> ChannelPublicKeys {
244 let from_secret = |s: &SecretKey| PublicKey::from_secret_key(secp_ctx, s);
246 funding_pubkey: from_secret(&funding_key),
247 revocation_basepoint: from_secret(&revocation_base_key),
248 payment_basepoint: from_secret(&payment_base_key),
249 delayed_payment_basepoint: from_secret(&delayed_payment_base_key),
250 htlc_basepoint: from_secret(&htlc_base_key),
255 impl ChannelKeys for InMemoryChannelKeys {
256 fn funding_key(&self) -> &SecretKey { &self.funding_key }
257 fn revocation_base_key(&self) -> &SecretKey { &self.revocation_base_key }
258 fn payment_base_key(&self) -> &SecretKey { &self.payment_base_key }
259 fn delayed_payment_base_key(&self) -> &SecretKey { &self.delayed_payment_base_key }
260 fn htlc_base_key(&self) -> &SecretKey { &self.htlc_base_key }
261 fn commitment_seed(&self) -> &[u8; 32] { &self.commitment_seed }
262 fn pubkeys<'a>(&'a self) -> &'a ChannelPublicKeys { &self.local_channel_pubkeys }
264 fn sign_remote_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
265 if commitment_tx.input.len() != 1 { return Err(()); }
267 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
268 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
269 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
271 let commitment_sighash = hash_to_message!(&bip143::SighashComponents::new(&commitment_tx).sighash_all(&commitment_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
272 let commitment_sig = secp_ctx.sign(&commitment_sighash, &self.funding_key);
274 let commitment_txid = commitment_tx.txid();
276 let mut htlc_sigs = Vec::with_capacity(htlcs.len());
277 for ref htlc in htlcs {
278 if let Some(_) = htlc.transaction_output_index {
279 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, feerate_per_kw, to_self_delay, htlc, &keys.a_delayed_payment_key, &keys.revocation_key);
280 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys);
281 let htlc_sighash = hash_to_message!(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]);
282 let our_htlc_key = match chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key) {
284 Err(_) => return Err(()),
286 htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &our_htlc_key));
290 Ok((commitment_sig, htlc_sigs))
293 fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
294 if closing_tx.input.len() != 1 { return Err(()); }
295 if closing_tx.input[0].witness.len() != 0 { return Err(()); }
296 if closing_tx.output.len() > 2 { return Err(()); }
298 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
299 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
300 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
302 let sighash = hash_to_message!(&bip143::SighashComponents::new(closing_tx)
303 .sighash_all(&closing_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
304 Ok(secp_ctx.sign(&sighash, &self.funding_key))
307 fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
308 let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
309 Ok(secp_ctx.sign(&msghash, &self.funding_key))
312 fn set_remote_channel_pubkeys(&mut self, channel_pubkeys: &ChannelPublicKeys) {
313 assert!(self.remote_channel_pubkeys.is_none(), "Already set remote channel pubkeys");
314 self.remote_channel_pubkeys = Some(channel_pubkeys.clone());
318 impl Writeable for InMemoryChannelKeys {
319 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
320 self.funding_key.write(writer)?;
321 self.revocation_base_key.write(writer)?;
322 self.payment_base_key.write(writer)?;
323 self.delayed_payment_base_key.write(writer)?;
324 self.htlc_base_key.write(writer)?;
325 self.commitment_seed.write(writer)?;
326 self.remote_channel_pubkeys.write(writer)?;
327 self.channel_value_satoshis.write(writer)?;
333 impl<R: ::std::io::Read> Readable<R> for InMemoryChannelKeys {
334 fn read(reader: &mut R) -> Result<Self, DecodeError> {
335 let funding_key = Readable::read(reader)?;
336 let revocation_base_key = Readable::read(reader)?;
337 let payment_base_key = Readable::read(reader)?;
338 let delayed_payment_base_key = Readable::read(reader)?;
339 let htlc_base_key = Readable::read(reader)?;
340 let commitment_seed = Readable::read(reader)?;
341 let remote_channel_pubkeys = Readable::read(reader)?;
342 let channel_value_satoshis = Readable::read(reader)?;
343 let secp_ctx = Secp256k1::signing_only();
344 let local_channel_pubkeys =
345 InMemoryChannelKeys::make_local_keys(&secp_ctx, &funding_key, &revocation_base_key,
346 &payment_base_key, &delayed_payment_base_key,
349 Ok(InMemoryChannelKeys {
353 delayed_payment_base_key,
356 channel_value_satoshis,
357 local_channel_pubkeys,
358 remote_channel_pubkeys
363 /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key
364 /// and derives keys from that.
366 /// Your node_id is seed/0'
367 /// ChannelMonitor closes may use seed/1'
368 /// Cooperative closes may use seed/2'
369 /// The two close keys may be needed to claim on-chain funds!
370 pub struct KeysManager {
371 secp_ctx: Secp256k1<secp256k1::SignOnly>,
372 node_secret: SecretKey,
373 destination_script: Script,
374 shutdown_pubkey: PublicKey,
375 channel_master_key: ExtendedPrivKey,
376 channel_child_index: AtomicUsize,
377 session_master_key: ExtendedPrivKey,
378 session_child_index: AtomicUsize,
379 channel_id_master_key: ExtendedPrivKey,
380 channel_id_child_index: AtomicUsize,
382 unique_start: Sha256State,
387 /// Constructs a KeysManager from a 32-byte seed. If the seed is in some way biased (eg your
388 /// RNG is busted) this may panic (but more importantly, you will possibly lose funds).
389 /// starting_time isn't strictly required to actually be a time, but it must absolutely,
390 /// without a doubt, be unique to this instance. ie if you start multiple times with the same
391 /// seed, starting_time must be unique to each run. Thus, the easiest way to achieve this is to
392 /// simply use the current time (with very high precision).
394 /// The seed MUST be backed up safely prior to use so that the keys can be re-created, however,
395 /// obviously, starting_time should be unique every time you reload the library - it is only
396 /// used to generate new ephemeral key data (which will be stored by the individual channel if
399 /// Note that the seed is required to recover certain on-chain funds independent of
400 /// ChannelMonitor data, though a current copy of ChannelMonitor data is also required for any
401 /// channel, and some on-chain during-closing funds.
403 /// Note that until the 0.1 release there is no guarantee of backward compatibility between
404 /// versions. Once the library is more fully supported, the docs will be updated to include a
405 /// detailed description of the guarantee.
406 pub fn new(seed: &[u8; 32], network: Network, logger: Arc<Logger>, starting_time_secs: u64, starting_time_nanos: u32) -> KeysManager {
407 let secp_ctx = Secp256k1::signing_only();
408 match ExtendedPrivKey::new_master(network.clone(), seed) {
410 let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key.key;
411 let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1).unwrap()) {
412 Ok(destination_key) => {
413 let pubkey_hash160 = Hash160::hash(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.key.serialize()[..]);
414 Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
415 .push_slice(&pubkey_hash160.into_inner())
418 Err(_) => panic!("Your RNG is busted"),
420 let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2).unwrap()) {
421 Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key.key,
422 Err(_) => panic!("Your RNG is busted"),
424 let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3).unwrap()).expect("Your RNG is busted");
425 let session_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4).unwrap()).expect("Your RNG is busted");
426 let channel_id_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(5).unwrap()).expect("Your RNG is busted");
428 let mut unique_start = Sha256::engine();
429 unique_start.input(&byte_utils::be64_to_array(starting_time_secs));
430 unique_start.input(&byte_utils::be32_to_array(starting_time_nanos));
431 unique_start.input(seed);
439 channel_child_index: AtomicUsize::new(0),
441 session_child_index: AtomicUsize::new(0),
442 channel_id_master_key,
443 channel_id_child_index: AtomicUsize::new(0),
449 Err(_) => panic!("Your rng is busted"),
454 impl KeysInterface for KeysManager {
455 type ChanKeySigner = InMemoryChannelKeys;
457 fn get_node_secret(&self) -> SecretKey {
458 self.node_secret.clone()
461 fn get_destination_script(&self) -> Script {
462 self.destination_script.clone()
465 fn get_shutdown_pubkey(&self) -> PublicKey {
466 self.shutdown_pubkey.clone()
469 fn get_channel_keys(&self, _inbound: bool, channel_value_satoshis: u64) -> InMemoryChannelKeys {
470 // We only seriously intend to rely on the channel_master_key for true secure
471 // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
472 // starting_time provided in the constructor) to be unique.
473 let mut sha = self.unique_start.clone();
475 let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
476 let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
477 sha.input(&child_privkey.private_key.key[..]);
479 let seed = Sha256::from_engine(sha).into_inner();
481 let commitment_seed = {
482 let mut sha = Sha256::engine();
484 sha.input(&b"commitment seed"[..]);
485 Sha256::from_engine(sha).into_inner()
487 macro_rules! key_step {
488 ($info: expr, $prev_key: expr) => {{
489 let mut sha = Sha256::engine();
491 sha.input(&$prev_key[..]);
492 sha.input(&$info[..]);
493 SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("SHA-256 is busted")
496 let funding_key = key_step!(b"funding key", commitment_seed);
497 let revocation_base_key = key_step!(b"revocation base key", funding_key);
498 let payment_base_key = key_step!(b"payment base key", revocation_base_key);
499 let delayed_payment_base_key = key_step!(b"delayed payment base key", payment_base_key);
500 let htlc_base_key = key_step!(b"HTLC base key", delayed_payment_base_key);
502 InMemoryChannelKeys::new(
507 delayed_payment_base_key,
510 channel_value_satoshis
514 fn get_onion_rand(&self) -> (SecretKey, [u8; 32]) {
515 let mut sha = self.unique_start.clone();
517 let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel);
518 let child_privkey = self.session_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
519 sha.input(&child_privkey.private_key.key[..]);
521 let mut rng_seed = sha.clone();
522 // Not exactly the most ideal construction, but the second value will get fed into
523 // ChaCha so it is another step harder to break.
524 rng_seed.input(b"RNG Seed Salt");
525 sha.input(b"Session Key Salt");
526 (SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted"),
527 Sha256::from_engine(rng_seed).into_inner())
530 fn get_channel_id(&self) -> [u8; 32] {
531 let mut sha = self.unique_start.clone();
533 let child_ix = self.channel_id_child_index.fetch_add(1, Ordering::AcqRel);
534 let child_privkey = self.channel_id_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
535 sha.input(&child_privkey.private_key.key[..]);
537 (Sha256::from_engine(sha).into_inner())