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Merge pull request #1660 from ethereum/dankrad-fix-custody

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Fix error in custody bit computation
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Danny Ryan 2020-03-16 09:55:28 -06:00 committed by GitHub
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1 changed files with 4 additions and 4 deletions
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specs/phase1/custody-game.md
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@ -192,10 +192,10 @@ def get_custody_atoms(bytez: bytes) -> Sequence[bytes]:
def compute_custody_bit(key: BLSSignature, data: bytes) -> bit: def compute_custody_bit(key: BLSSignature, data: bytes) -> bit:
full_G2_element = bls.signature_to_G2(key) full_G2_element = bls.signature_to_G2(key)
s = full_G2_element[0].coeffs s = full_G2_element[0].coeffs
bits = [legendre_bit(sum(s[i % 2]**i * int.from_bytes(atom, "little")), BLS12_381_Q) custody_atoms = get_custody_atoms(data)
for i, atom in enumerate(get_custody_atoms(data))] n = len(custody_atoms)
# XOR all atom bits a = sum(s[i % 2]**i * int.from_bytes(atom, "little") for i, atom in enumerate(custody_atoms) + s[n % 2]**n)
return bit(sum(bits) % 2) return legendre_bit(a, BLS12_381_Q)
``` ```
### `get_randao_epoch_for_custody_period` ### `get_randao_epoch_for_custody_period`