def generate_tx_spend_and_key_image(
ack: AccountCreds,
out_key: Ge25519,
recv_derivation: Ge25519,
real_output_index: int,
received_index: Tuple[int, int],
) -> Optional[Tuple[Sc25519, Ge25519]]:
"""
Generates UTXO spending key and key image.
Corresponds to generate_key_image_helper_precomp() in the Monero codebase.
:param ack: sender credentials
:type ack: apps.monero.xmr.credentials.AccountCreds
:param out_key: real output (from input RCT) destination key
:param recv_derivation:
:param real_output_index:
:param received_index: subaddress index this payment was received to
:return:
"""
if not crypto.sc_isnonzero(ack.spend_key_private):
raise ValueError("Watch-only wallet not supported")
# derive secret key with subaddress - step 1: original CN derivation
scalar_step1 = crypto.derive_secret_key(
recv_derivation, real_output_index, ack.spend_key_private
)
# step 2: add Hs(SubAddr || a || index_major || index_minor)
subaddr_sk = None
if received_index == (0, 0):
scalar_step2 = scalar_step1
else:
subaddr_sk = get_subaddress_secret_key(
ack.view_key_private, major=received_index[0], minor=received_index[1]
)
scalar_step2 = crypto.sc_add(scalar_step1, subaddr_sk)
# When not in multisig, we know the full spend secret key, so the output pubkey can be obtained by scalarmultBase
pub_ver = crypto.scalarmult_base(scalar_step2)
# <Multisig>, branch deactivated until implemented
# # When in multisig, we only know the partial spend secret key. But we do know the full spend public key,
# # so the output pubkey can be obtained by using the standard CN key derivation.
# pub_ver = crypto.derive_public_key(
# recv_derivation, real_output_index, ack.spend_key_public
# )
#
# # Add the contribution from the subaddress part
# if received_index != (0, 0):
# subaddr_pk = crypto.scalarmult_base(subaddr_sk)
# pub_ver = crypto.point_add(pub_ver, subaddr_pk)
# </Multisig>
if not crypto.point_eq(pub_ver, out_key):
raise ValueError(
"key image helper precomp: given output pubkey doesn't match the derived one"
)
ki = generate_key_image(crypto.encodepoint(pub_ver), scalar_step2)
return scalar_step2, ki
def check_ring_singature(prefix_hash, image, pubs, sig):
"""
Checks ring signature generated with generate_ring_signature
:param prefix_hash:
:param image:
:param pubs:
:param sig:
:return:
"""
from apps.monero.xmr.common import memcpy
image_unp = crypto.ge_frombytes_vartime(image)
image_pre = crypto.ge_dsm_precomp(image_unp)
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()
for i in range(len(pubs)):
if crypto.sc_check(sig[i][0]) != 0 or crypto.sc_check(sig[i][1]) != 0:
return False
tmp3 = crypto.ge_frombytes_vartime(pubs[i])
tmp2 = crypto.ge_double_scalarmult_base_vartime(
sig[i][0], tmp3, sig[i][1])
crypto.encodepoint_into(tmp2, mvbuff[buff_off:buff_off + 32])
buff_off += 32
tmp3 = crypto.hash_to_ec(crypto.encodepoint(pubs[i]))
tmp2 = crypto.ge_double_scalarmult_precomp_vartime(
sig[i][1], tmp3, sig[i][0], image_pre)
crypto.encodepoint_into(tmp2, mvbuff[buff_off:buff_off + 32])
buff_off += 32
sum = crypto.sc_add(sum, sig[i][0])
h = crypto.hash_to_scalar(buff)
h = crypto.sc_sub(h, sum)
return crypto.sc_isnonzero(h) == 0