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 _encrypt_payment_id(payment_id, public_key, secret_key):
"""
Encrypts payment_id hex.
Used in the transaction extra. Only recipient is able to decrypt.
"""
derivation_p = crypto.generate_key_derivation(public_key, secret_key)
derivation = bytearray(33)
derivation = crypto.encodepoint_into(derivation, derivation_p)
derivation[32] = 0x8D # ENCRYPTED_PAYMENT_ID_TAIL
hash = crypto.cn_fast_hash(derivation)
pm_copy = bytearray(payment_id)
return crypto.xor8(pm_copy, hash)
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
