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Update 1_custody-game.md

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Justin 2019-05-20 09:29:09 +01:00 committed by GitHub
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specs/core/1_custody-game.md
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@ -254,12 +254,10 @@ The `empty` function accepts and SSZ type as input and returns an object of that
### `get_crosslink_chunk_count` ### `get_crosslink_chunk_count`
```python ```python
def get_custody_chunk_count(attestation: Attestation) -> int: def get_custody_chunk_count(crosslink: Crosslink) -> int:
crosslink_start_epoch = attestation.data.latest_crosslink.start_epoch crosslink_length = min(MAX_EPOCHS_PER_CROSSLINK, crosslink.end_epoch - crosslink.start_epoch)
crosslink_end_epoch = attestation.data.latest_crosslink.end_epoch
crosslink_crosslink_length = min(MAX_EPOCHS_PER_CROSSLINK, end_epoch - start_epoch)
chunks_per_epoch = 2 * BYTES_PER_SHARD_BLOCK * SLOTS_PER_EPOCH // BYTES_PER_CUSTODY_CHUNK chunks_per_epoch = 2 * BYTES_PER_SHARD_BLOCK * SLOTS_PER_EPOCH // BYTES_PER_CUSTODY_CHUNK
return crosslink_crosslink_length * chunks_per_epoch return crosslink_length * chunks_per_epoch
``` ```
### `get_custody_chunk_bit` ### `get_custody_chunk_bit`
@ -470,7 +468,7 @@ def process_chunk_challenge(state: BeaconState,
record.chunk_index != challenge.chunk_index record.chunk_index != challenge.chunk_index
) )
# Verify depth # Verify depth
depth = math.log2(next_power_of_two(get_custody_chunk_count(challenge.attestation))) depth = math.log2(next_power_of_two(get_custody_chunk_count(challenge.attestation.data.crosslink)))
assert challenge.chunk_index < 2**depth assert challenge.chunk_index < 2**depth
# Add new chunk challenge record # Add new chunk challenge record
new_record = CustodyChunkChallengeRecord( new_record = CustodyChunkChallengeRecord(
@ -544,7 +542,7 @@ def process_bit_challenge(state: BeaconState,
) )
# Verify the chunk count # Verify the chunk count
chunk_count = get_custody_chunk_count(challenge.attestation) chunk_count = get_custody_chunk_count(challenge.attestation.data.crosslink)
assert verify_bitfield(challenge.chunk_bits, chunk_count) assert verify_bitfield(challenge.chunk_bits, chunk_count)
# Verify the first bit of the hash of the chunk bits does not equal the custody bit # Verify the first bit of the hash of the chunk bits does not equal the custody bit
custody_bit = get_bitfield_bit(attestation.custody_bitfield, attesters.index(responder_index)) custody_bit = get_bitfield_bit(attestation.custody_bitfield, attesters.index(responder_index))