def derive_subaddress_public_key(out_key, derivation, output_index):
"""
out_key - H_s(derivation || varint(output_index))G
"""
crypto.check_ed25519point(out_key)
scalar = crypto.derivation_to_scalar(derivation, output_index)
point2 = crypto.scalarmult_base(scalar)
point4 = crypto.point_sub(out_key, point2)
return point4
def generate_ring_signature(
prefix_hash: bytes,
image: Ge25519,
pubs: list[Ge25519],
sec: Sc25519,
sec_idx: int,
test: bool = False,
) -> Sig:
"""
Generates ring signature with key image.
void crypto_ops::generate_ring_signature()
"""
from trezor.utils import memcpy
if test:
t = crypto.scalarmult_base(sec)
if not crypto.point_eq(t, pubs[sec_idx]):
raise ValueError("Invalid sec key")
k_i = monero.generate_key_image(crypto.encodepoint(pubs[sec_idx]), sec)
if not crypto.point_eq(k_i, image):
raise ValueError("Key image invalid")
for k in pubs:
crypto.check_ed25519point(k)
buff_off = len(prefix_hash)
buff = bytearray(buff_off + 2 * 32 * len(pubs))
memcpy(buff, 0, prefix_hash, 0, buff_off)
mvbuff = memoryview(buff)
sum = crypto.sc_0()
k = crypto.sc_0()
sig = []
for _ in range(len(pubs)):
sig.append([crypto.sc_0(), crypto.sc_0()]) # c, r
for i in range(len(pubs)):
if i == sec_idx:
k = crypto.random_scalar()
tmp3 = crypto.scalarmult_base(k)
crypto.encodepoint_into(mvbuff[buff_off:buff_off + 32], tmp3)
buff_off += 32
tmp3 = crypto.hash_to_point(crypto.encodepoint(pubs[i]))
tmp2 = crypto.scalarmult(tmp3, k)
crypto.encodepoint_into(mvbuff[buff_off:buff_off + 32], tmp2)
buff_off += 32
else:
sig[i] = [crypto.random_scalar(), crypto.random_scalar()]
tmp3 = pubs[i]
tmp2 = crypto.ge25519_double_scalarmult_base_vartime(
sig[i][0], tmp3, sig[i][1])
crypto.encodepoint_into(mvbuff[buff_off:buff_off + 32], tmp2)
buff_off += 32
tmp3 = crypto.hash_to_point(crypto.encodepoint(tmp3))
tmp2 = crypto.ge25519_double_scalarmult_vartime2(
sig[i][1], tmp3, sig[i][0], image)
crypto.encodepoint_into(mvbuff[buff_off:buff_off + 32], tmp2)
buff_off += 32
sum = crypto.sc_add(sum, sig[i][0])
h = crypto.hash_to_scalar(buff)
sig[sec_idx][0] = crypto.sc_sub(h, sum)
sig[sec_idx][1] = crypto.sc_mulsub(sig[sec_idx][0], sec, k)
return sig