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refactor/rework key derivation (#652)

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seed -> ext_key -> many child_keys
This commit is contained in:
Antioch Peverell 2018-01-25 15:19:32 -05:00 committed by GitHub
parent 2def215553
commit 5a7d22977e
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 105 additions and 93 deletions
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4
core/src/core/transaction.rs
View file

@ -1057,7 +1057,7 @@ mod test {
).unwrap();
let short_id = input.short_id(&block_hash);
assert_eq!(short_id, ShortId::from_hex("102864956811").unwrap());
assert_eq!(short_id, ShortId::from_hex("3e1262905b7a").unwrap());
// now generate the short_id for a *very* similar output (single feature flag different)
// and check it generates a different short_id
@ -1072,6 +1072,6 @@ mod test {
).unwrap();
let short_id = input.short_id(&block_hash);
assert_eq!(short_id, ShortId::from_hex("b8c189165df1").unwrap());
assert_eq!(short_id, ShortId::from_hex("90653c1c870a").unwrap());
}
}

148
keychain/src/extkey.rs
View file

@ -126,12 +126,20 @@ impl Identifier {
Identifier(identifier)
}
pub fn from_key_id(secp: &Secp256k1, pubkey: &PublicKey) -> Identifier {
pub fn from_pubkey(secp: &Secp256k1, pubkey: &PublicKey) -> Identifier {
let bytes = pubkey.serialize_vec(secp, true);
let identifier = blake2b(IDENTIFIER_SIZE, &[], &bytes[..]);
Identifier::from_bytes(&identifier.as_bytes())
}
/// Return the identifier of the secret key
/// which is the blake2b (10 byte) digest of the PublicKey
/// corresponding to the secret key provided.
fn from_secret_key(secp: &Secp256k1, key: &SecretKey) -> Result<Identifier, Error> {
let key_id = PublicKey::from_secret_key(secp, key)?;
Ok(Identifier::from_pubkey(secp, &key_id))
}
fn from_hex(hex: &str) -> Result<Identifier, Error> {
let bytes = util::from_hex(hex.to_string()).unwrap();
Ok(Identifier::from_bytes(&bytes))
@ -162,6 +170,20 @@ impl fmt::Display for Identifier {
}
}
#[derive(Debug, Clone)]
pub struct ChildKey {
/// Child number of the key (n derivations)
pub n_child: u32,
/// Root key id
pub root_key_id: Identifier,
/// Key id
pub key_id: Identifier,
/// The private key
pub key: SecretKey,
/// The key used for generating the associated switch_commit_hash
pub switch_key: [u8; 32],
}
/// An ExtendedKey is a secret key which can be used to derive new
/// secret keys to blind the commitment of a transaction output.
/// To be usable, a secret key should have an amount assigned to it,
@ -169,20 +191,20 @@ impl fmt::Display for Identifier {
/// given.
#[derive(Debug, Clone)]
pub struct ExtendedKey {
/// Depth of the extended key
pub depth: u8,
/// Child number of the key
/// Child number of the extended key
pub n_child: u32,
/// Root key identifier
/// Root key id
pub root_key_id: Identifier,
/// Actual private key
/// Key id
pub key_id: Identifier,
/// The secret key
pub key: SecretKey,
/// Code of the derivation chain
pub chaincode: [u8; 32],
/// The bytes of the key used for generating the associated switch_commit_hash
/// The chain code for the key derivation chain
pub chain_code: [u8; 32],
/// The key used for generating the associated switch_commit_hash
pub switch_key: [u8; 32],
/// Code of the derivation chain for the switch_commit_hash key
pub switch_chaincode: [u8; 32],
/// The chain code for the switch key derivation chain
pub switch_chain_code: [u8; 32],
}
impl ExtendedKey {
@ -196,14 +218,15 @@ impl ExtendedKey {
let derived = blake2b(64, b"Grin/MW Seed", seed);
let slice = derived.as_bytes();
// TODO Error handling
let key = SecretKey::from_slice(&secp, &slice[0..32])
.expect("Error generating from seed");
.expect("Error deriving key (from_slice)");
let mut chaincode: [u8; 32] = Default::default();
(&mut chaincode).copy_from_slice(&slice[32..64]);
let mut chain_code: [u8; 32] = Default::default();
(&mut chain_code).copy_from_slice(&slice[32..64]);
// Now derive the switch_key and switch_chaincode in a similar fashion
let key_id = Identifier::from_secret_key(secp, &key)?;
// Now derive the switch_key and switch_chain_code in a similar fashion
// but using a different key to ensure there is nothing linking
// the secret key and the switch commit hash key for any extended key
// we subsequently derive
@ -212,75 +235,67 @@ impl ExtendedKey {
let mut switch_key: [u8; 32] = Default::default();
(&mut switch_key).copy_from_slice(&switch_slice[0..32]);
let mut switch_chaincode: [u8; 32] = Default::default();
(&mut switch_chaincode).copy_from_slice(&switch_slice[32..64]);
let mut ext_key = ExtendedKey {
depth: 0,
root_key_id: Identifier::zero(),
let mut switch_chain_code: [u8; 32] = Default::default();
(&mut switch_chain_code).copy_from_slice(&switch_slice[32..64]);
let ext_key = ExtendedKey {
n_child: 0,
key,
chaincode,
switch_key,
switch_chaincode,
};
root_key_id: key_id.clone(),
key_id: key_id.clone(),
ext_key.root_key_id = ext_key.identifier(secp)?;
// key and extended chain code for the key itself
key,
chain_code,
// key and extended chain code for the key for hashed switch commitments
switch_key,
switch_chain_code,
};
Ok(ext_key)
}
/// Return the identifier of the key
/// which is the blake2b (10 byte) digest of the PublicKey
// corresponding to the underlying SecretKey
pub fn identifier(&self, secp: &Secp256k1) -> Result<Identifier, Error> {
let key_id = PublicKey::from_secret_key(secp, &self.key)?;
Ok(Identifier::from_key_id(secp, &key_id))
}
/// Derive an extended key from an extended key
pub fn derive(&self, secp: &Secp256k1, n: u32) -> Result<ExtendedKey, Error> {
/// Derive a child key from this extended key
pub fn derive(&self, secp: &Secp256k1, n: u32) -> Result<ChildKey, Error> {
let mut n_bytes: [u8; 4] = [0; 4];
BigEndian::write_u32(&mut n_bytes, n);
let mut seed = self.key[..].to_vec();
seed.extend_from_slice(&n_bytes);
let derived = blake2b(64, &self.chaincode[..], &seed[..]);
let slice = derived.as_bytes();
// only need a 32 byte digest here as we only need the bytes for the key itself
// we do not need additional bytes for a derived (and unused) chain code
let derived = blake2b(32, &self.chain_code[..], &seed[..]);
let mut key = SecretKey::from_slice(&secp, &slice[0..32])
.expect("Error deriving key");
let mut key = SecretKey::from_slice(&secp, &derived.as_bytes()[..])
.expect("Error deriving key (from_slice)");
key.add_assign(secp, &self.key)
.expect("Error deriving key");
.expect("Error deriving key (add_assign)");
let mut chaincode: [u8; 32] = Default::default();
(&mut chaincode).copy_from_slice(&slice[32..64]);
let key_id = Identifier::from_secret_key(secp, &key)?;
// Now derive the switch_key and switch_chaincode in a similar fashion
let mut switch_seed = self.switch_key[..].to_vec();
switch_seed.extend_from_slice(&n_bytes);
let switch_derived = blake2b(64, &self.switch_chaincode[..], &switch_seed[..]);
let switch_slice = switch_derived.as_bytes();
// only need a 32 byte digest here as we only need the bytes for the key itself
// we do not need additional bytes for a derived (and unused) chain code
let switch_derived = blake2b(32, &self.switch_chain_code[..], &switch_seed[..]);
let mut switch_key: [u8; 32] = Default::default();
(&mut switch_key).copy_from_slice(&switch_slice[0..32]);
let mut switch_chaincode: [u8; 32] = Default::default();
(&mut switch_chaincode).copy_from_slice(&switch_slice[32..64]);
(&mut switch_key).copy_from_slice(&switch_derived.as_bytes()[..]);
// TODO check if key != 0 ?
Ok(ExtendedKey {
depth: self.depth + 1,
root_key_id: self.identifier(&secp)?,
Ok(ChildKey {
n_child: n,
root_key_id: self.root_key_id.clone(),
key_id,
key,
chaincode,
switch_key,
switch_chaincode,
})
}
}
#[cfg(test)]
mod test {
use serde_json;
@ -321,22 +336,20 @@ mod test {
let extk = ExtendedKey::from_seed(&s, &seed.as_slice()).unwrap();
let sec = from_hex("2878a92133b0a7c2fbfb0bd4520ed2e55ea3fa2913200f05c30077d30b193480");
let secret_key = SecretKey::from_slice(&s, sec.as_slice()).unwrap();
let chaincode =
let chain_code =
from_hex("3ad40dd836c5ce25dfcbdee5044d92cf6b65bd5475717fa7a56dd4a032cca7c0");
let identifier = from_hex("6f7c1a053ca54592e783");
let depth = 0;
let n_child = 0;
assert_eq!(extk.key, secret_key);
assert_eq!(
extk.identifier(&s).unwrap(),
extk.key_id,
Identifier::from_bytes(identifier.as_slice())
);
assert_eq!(
extk.root_key_id,
Identifier::from_bytes(identifier.as_slice())
);
assert_eq!(extk.chaincode, chaincode.as_slice());
assert_eq!(extk.depth, depth);
assert_eq!(extk.chain_code, chain_code.as_slice());
assert_eq!(extk.n_child, n_child);
}
@ -346,25 +359,20 @@ mod test {
let seed = from_hex("000102030405060708090a0b0c0d0e0f");
let extk = ExtendedKey::from_seed(&s, &seed.as_slice()).unwrap();
let derived = extk.derive(&s, 0).unwrap();
let sec = from_hex("2676a3ab2ded7c79cbd0bd26d448698de5da5af8e809080d3cacfa2ee31a9aa7");
let sec = from_hex("55f1a2b67ec58933bf954fdc721327afe486e8989af923c3ae298e45a84ef597");
let secret_key = SecretKey::from_slice(&s, sec.as_slice()).unwrap();
let chaincode =
from_hex("9bc90b148f4c9478205d6ca72c58bbda2902be1e5082de05d56339a74a5314a3");
let root_key_id = from_hex("6f7c1a053ca54592e783");
let identifier = from_hex("5f2ec8ee00e8bca002fa");
let depth = 1;
let identifier = from_hex("8fa188b56cefe66be154");
let n_child = 0;
assert_eq!(derived.key, secret_key);
assert_eq!(
derived.identifier(&s).unwrap(),
derived.key_id,
Identifier::from_bytes(identifier.as_slice())
);
assert_eq!(
derived.root_key_id,
Identifier::from_bytes(root_key_id.as_slice())
);
assert_eq!(derived.chaincode, chaincode.as_slice());
assert_eq!(derived.depth, depth);
assert_eq!(derived.n_child, n_child);
}
}

46
keychain/src/keychain.rs
View file

@ -106,9 +106,8 @@ impl Keychain {
}
pub fn derive_key_id(&self, derivation: u32) -> Result<Identifier, Error> {
let extkey = self.extkey.derive(&self.secp, derivation)?;
let key_id = extkey.identifier(&self.secp)?;
Ok(key_id)
let child_key = self.extkey.derive(&self.secp, derivation)?;
Ok(child_key.key_id)
}
fn derived_key(&self, key_id: &Identifier) -> Result<SecretKey, Error> {
@ -118,11 +117,11 @@ impl Keychain {
return Ok(*key);
}
let extkey = self.derived_extended_key(key_id)?;
Ok(extkey.key)
let child_key = self.derived_child_key(key_id)?;
Ok(child_key.key)
}
fn derived_extended_key(&self, key_id: &Identifier) -> Result<extkey::ExtendedKey, Error> {
fn derived_child_key(&self, key_id: &Identifier) -> Result<extkey::ChildKey, Error> {
trace!(LOGGER, "Derived Key by key_id: {}", key_id);
// then check the derivation cache to see if we have previously derived this key
@ -142,22 +141,27 @@ impl Keychain {
{
let mut cache = self.key_derivation_cache.write().unwrap();
for i in 1..100_000 {
let extkey = self.extkey.derive(&self.secp, i)?;
let extkey_id = extkey.identifier(&self.secp)?;
let child_key = self.extkey.derive(&self.secp, i)?;
// let child_key_id = extkey.identifier(&self.secp)?;
if !cache.contains_key(&extkey_id) {
trace!(LOGGER, "... Derived Key (cache miss) key_id: {}, derivation: {}", extkey_id, extkey.n_child);
cache.insert(extkey_id.clone(), extkey.n_child);
if !cache.contains_key(&child_key.key_id) {
trace!(
LOGGER,
"... Derived Key (cache miss) key_id: {}, derivation: {}",
child_key.key_id,
child_key.n_child,
);
cache.insert(child_key.key_id.clone(), child_key.n_child);
}
if extkey_id == *key_id {
return Ok(extkey);
if child_key.key_id == *key_id {
return Ok(child_key);
}
}
}
Err(Error::KeyDerivation(
format!("cannot find extkey for {:?}", key_id),
format!("failed to derive child_key for {:?}", key_id),
))
}
@ -165,10 +169,10 @@ impl Keychain {
fn derived_key_from_index(
&self,
derivation: u32,
) -> Result<extkey::ExtendedKey, Error> {
) -> Result<extkey::ChildKey, Error> {
trace!(LOGGER, "Derived Key (fast) by derivation: {}", derivation);
let extkey = self.extkey.derive(&self.secp, derivation)?;
return Ok(extkey)
let child_key = self.extkey.derive(&self.secp, derivation)?;
return Ok(child_key)
}
pub fn commit(&self, amount: u64, key_id: &Identifier) -> Result<Commitment, Error> {
@ -182,8 +186,8 @@ impl Keychain {
amount: u64,
derivation: u32,
) -> Result<Commitment, Error> {
let extkey = self.derived_key_from_index(derivation)?;
let commit = self.secp.commit(amount, extkey.key)?;
let child_key = self.derived_key_from_index(derivation)?;
let commit = self.secp.commit(amount, child_key.key)?;
Ok(commit)
}
@ -210,8 +214,8 @@ impl Keychain {
return Ok(key);
}
let extkey = self.derived_extended_key(key_id)?;
Ok(extkey.switch_key)
let child_key = self.derived_child_key(key_id)?;
Ok(child_key.switch_key)
}
pub fn range_proof(