def signature2(m, sk):
assert len(sk) == 32
h = H(sk[:32])
a_bytes, inter = h[:32], h[32:]
a = bytes_to_clamped_scalar(a_bytes)
r = Hint(inter + m)
R = Base.scalarmult(r)
R_bytes = R.to_bytes()
S = r + Hint(R_bytes + m) * a
return R_bytes + scalar_to_bytes(S)
def signature(m,sk,pk):
assert len(sk) == 32 # seed
assert len(pk) == 32
h = H(sk[:32])
a_bytes, inter = h[:32], h[32:]
a = bytes_to_clamped_scalar(a_bytes)
r = Hint(inter + m)
R = Base.scalarmult(r)
R_bytes = R.to_bytes()
S = r + Hint(R_bytes + pk + m) * a
return R_bytes + scalar_to_bytes(S)
def sign_ed25519(f: BinaryIO, private_key: bytes) -> bytes:
"""
Signs file-like object using a private key, defined in a very special way, compatible to crypto library, used by sign_update in Sparkle
:param f: file-like object to be signed
:param private_key: 96 bytes, concatenated private_scalar=a, sha512_right_half=RH, pubkey=A
:return: signature
"""
from pure25519.basic import bytes_to_clamped_scalar, Base, scalar_to_bytes
assert len(private_key) == 96
a_bytes, RH, public_key = private_key[:32], private_key[
32:64], private_key[64:]
a = bytes_to_clamped_scalar(a_bytes)
r = hashlib.sha512()
r.update(RH)
f.seek(0)
for block in iter(partial(f.read, FILE_BLOCK_SIZE), b""):
r.update(block)
r = int.from_bytes(r.digest(), "little")
R = Base.scalarmult(r)
R_bytes = R.to_bytes()
RAM_hashed = hashlib.sha512()
RAM_hashed.update(R_bytes)
RAM_hashed.update(public_key)
f.seek(0)
for block in iter(partial(f.read, FILE_BLOCK_SIZE), b""):
RAM_hashed.update(block)
RAM_hashed = int.from_bytes(RAM_hashed.digest(), "little")
S = r + RAM_hashed * a
return R_bytes + scalar_to_bytes(S)
def publickey(seed):
# turn first half of SHA512(seed) into scalar, then into point
assert len(seed) == 32
a = bytes_to_clamped_scalar(H(seed)[:32])
A = Base.scalarmult(a)
return A.to_bytes()
def _get_private_key_as_scalar(priv):
h = dhh(priv.sk_s[:32]) # Hash the seed (the first 32 bytes of sk_s)
a_bytes = h[:32] # The first 32 bytes of the hash is used as the secret key
return bytes_to_clamped_scalar(a_bytes) # return key as a scalar
def publickey(seed):
# turn first half of SHA512(seed) into scalar, then into point
assert len(seed) == 32
a = bytes_to_clamped_scalar(H(seed)[:32])
A = Base.scalarmult(a)
return A.to_bytes()
