def _ecdh_encode(amount: int, amount_key: bytes) -> EcdhTuple:
"""
Output recipients decode amounts from EcdhTuple structure.
"""
from apps.monero.xmr.serialize_messages.tx_ecdh import EcdhTuple
ecdh_info = EcdhTuple(mask=crypto.NULL_KEY_ENC, amount=bytearray(32))
amnt = crypto.sc_init(amount)
crypto.encodeint_into(ecdh_info.amount, amnt)
crypto.xor8(ecdh_info.amount, _ecdh_hash(amount_key))
return ecdh_info
def ecdh_decode(masked, receiver_sk=None, derivation=None):
"""
Elliptic Curve Diffie-Helman: encodes and decodes the amount b and mask a
where C= aG + bH
:param masked:
:param receiver_sk:
:param derivation:
:return:
"""
from apps.monero.xmr.serialize_messages.tx_ecdh import EcdhTuple
rv = EcdhTuple()
if derivation is None:
derivation = crypto.scalarmult(masked.senderPk, receiver_sk)
sharedSec1 = crypto.hash_to_scalar(derivation)
sharedSec2 = crypto.hash_to_scalar(crypto.encodeint(sharedSec1))
rv.mask = crypto.sc_sub(masked.mask, sharedSec1)
rv.amount = crypto.sc_sub(masked.amount, sharedSec2)
return rv
def _ecdh_encode(mask, amount, amount_key):
"""
Output recipients need be able to reconstruct the amount commitments.
This means the blinding factor `mask` and `amount` must be communicated
to the receiver somehow.
The mask and amount are stored as:
- mask = mask + Hs(amount_key)
- amount = amount + Hs(Hs(amount_key))
Because the receiver can derive the `amount_key` they can
easily derive both mask and amount as well.
"""
from apps.monero.xmr.serialize_messages.tx_ecdh import EcdhTuple
ecdh_info = EcdhTuple(mask=mask, amount=crypto.sc_init(amount))
amount_key_hash_single = crypto.hash_to_scalar(amount_key)
amount_key_hash_double = crypto.hash_to_scalar(
crypto.encodeint(amount_key_hash_single))
ecdh_info.mask = crypto.sc_add(ecdh_info.mask, amount_key_hash_single)
ecdh_info.amount = crypto.sc_add(ecdh_info.amount, amount_key_hash_double)
return _recode_ecdh(ecdh_info)
def _ecdh_encode(mask, amount, amount_key, v2=False):
"""
Output recipients need be able to reconstruct the amount commitments.
This means the blinding factor `mask` and `amount` must be communicated
to the receiver somehow.
The mask and amount are stored as:
- mask = mask + Hs(amount_key)
- amount = amount + Hs(Hs(amount_key))
Because the receiver can derive the `amount_key` they can
easily derive both mask and amount as well.
"""
from apps.monero.xmr.serialize_messages.tx_ecdh import EcdhTuple
ecdh_info = EcdhTuple(mask=mask, amount=crypto.sc_init(amount))
if v2:
amnt = ecdh_info.amount
ecdh_info.mask = crypto.NULL_KEY_ENC
ecdh_info.amount = bytearray(32)
crypto.encodeint_into(ecdh_info.amount, amnt)
crypto.xor8(ecdh_info.amount, _ecdh_hash(amount_key))
return ecdh_info
else:
amount_key_hash_single = crypto.hash_to_scalar(amount_key)
amount_key_hash_double = crypto.hash_to_scalar(
crypto.encodeint(amount_key_hash_single))
# Not modifying passed mask, is reused in BP.
ecdh_info.mask = crypto.sc_add(ecdh_info.mask, amount_key_hash_single)
crypto.sc_add_into(ecdh_info.amount, ecdh_info.amount,
amount_key_hash_double)
ecdh_info.mask = crypto.encodeint(ecdh_info.mask)
ecdh_info.amount = crypto.encodeint(ecdh_info.amount)
return ecdh_info
