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Refactor universal hash function

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Dankrad Feist 2020-06-12 12:04:30 +01:00
parent 65c3417f90
commit 59b35afcd9
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1 changed files with 16 additions and 9 deletions
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specs/phase1/custody-game.md
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@ -256,19 +256,26 @@ def get_custody_secrets(key: BLSSignature) -> Sequence[int]:
return secrets return secrets
``` ```
### `universal_hash_function`
```python
def universal_hash_function(data_chunks: Sequence[bytes], secrets: Sequence[int]) -> int:
n = len(data_chunks)
return (
sum(
secrets[i % CUSTODY_SECRETS]**i * int.from_bytes(atom, "little") % CUSTODY_PRIME
for i, atom in enumerate(data_chunks)
) + secrets[n % CUSTODY_SECRETS]**n
) % CUSTODY_PRIME
```
### `compute_custody_bit` ### `compute_custody_bit`
```python ```python
def compute_custody_bit(key: BLSSignature, data: ByteList[MAX_SHARD_BLOCK_SIZE]) -> bit: def compute_custody_bit(key: BLSSignature, data: ByteList[MAX_SHARD_BLOCK_SIZE]) -> bit:
secrets = get_custody_secrets(key)
custody_atoms = get_custody_atoms(data) custody_atoms = get_custody_atoms(data)
n = len(custody_atoms) secrets = get_custody_secrets(key)
uhf = ( uhf = universal_hash_function(custody_atoms, secrets)
sum(
secrets[i % CUSTODY_SECRETS]**i * int.from_bytes(atom, "little") % CUSTODY_PRIME
for i, atom in enumerate(custody_atoms)
) + secrets[n % CUSTODY_SECRETS]**n
) % CUSTODY_PRIME
return legendre_bit(uhf + secrets[0], CUSTODY_PRIME) return legendre_bit(uhf + secrets[0], CUSTODY_PRIME)
``` ```
@ -579,7 +586,7 @@ def process_challenge_deadlines(state: BeaconState) -> None:
for custody_chunk_challenge in state.custody_chunk_challenge_records: for custody_chunk_challenge in state.custody_chunk_challenge_records:
if get_current_epoch(state) > custody_chunk_challenge.inclusion_epoch + CUSTODY_RESPONSE_DEADLINE: if get_current_epoch(state) > custody_chunk_challenge.inclusion_epoch + CUSTODY_RESPONSE_DEADLINE:
slash_validator(state, custody_chunk_challenge.responder_index, custody_chunk_challenge.challenger_index) slash_validator(state, custody_chunk_challenge.responder_index, custody_chunk_challenge.challenger_index)
index_in_records = records.index(custody_chunk_challenge) index_in_records = state.custody_chunk_challenge_records.index(custody_chunk_challenge)
state.custody_chunk_challenge_records[index_in_records] = CustodyChunkChallengeRecord() state.custody_chunk_challenge_records[index_in_records] = CustodyChunkChallengeRecord()
``` ```