def decrypt_message(bip32, address_n, nonce_pub, payload, msg_hmac):
priv_node = bip32.get_private_node(address_n)
priv_key = tools.EcKey(priv_node.private_key)
shared_secret_point = tools.public_key_to_point(nonce_pub) * priv_key.privkey.secret_multiplier
shared_secret = tools.point_to_public_key(shared_secret_point, True)
keying_bytes = PBKDF2(shared_secret, "Bitcoin Secure Message" + nonce_pub, iterations=2048, macmodule=hmac, digestmodule=sha256).read(80)
aes_key = keying_bytes[:32]
hmac_key = keying_bytes[32:64]
aes_iv = keying_bytes[64:]
msg_hmac_new = hmac.HMAC(key=hmac_key, msg=payload, digestmod=sha256).digest()[:8]
if msg_hmac_new != msg_hmac:
raise Exception('Message_HMAC does not match')
decrypter = pyaes.Decrypter(pyaes.AESModeOfOperationCFB(key=aes_key, iv=aes_iv, segment_size=16))
payload = decrypter.feed(payload) + decrypter.feed()
if not ord(payload[0]) in [0x00, 0x01, 0x80, 0x81]:
raise Exception('AES decryption failed')
signing = (ord(payload[0]) & 0x01) > 0
display_only = (ord(payload[0]) & 0x80) > 0
if signing:
message = tools.deser_length_string(payload[1:-(21+65)])
address_bin = payload[-(21+65):-65]
signature = payload[-65:]
address = tools.hash_160_to_bc_address(address_bin[1:], ord(address_bin[0]))
verify_message(address, signature, message)
else:
message = tools.deser_length_string(payload[1:])
address = None
return (message, address, display_only)
def encrypt_message(pubkey, message, display_only, bip32, coin, address_n):
if len(address_n) > 0:
priv_node = bip32.get_private_node(address_n)
priv_key = tools.EcKey(priv_node.private_key)
signing = True
else:
signing = False
if signing:
if display_only:
payload = chr(0x80 + 1)
else:
payload = chr(1)
address, signature = sign_message(bip32, coin, address_n, message)
address_bin = tools.bc_address_decode(address)[:21]
payload += tools.ser_length(len(message)) + message + address_bin + signature
else:
if display_only:
payload = chr(0x80)
else:
payload = chr(0)
payload += tools.ser_length(len(message)) + message
nonce = tools.get_local_entropy()
nonce_key = tools.EcKey(nonce)
nonce_pub = binascii.unhexlify(nonce_key.get_public_key(True))
dest_pub = tools.public_key_to_point(pubkey)
shared_secret_point = dest_pub * nonce_key.privkey.secret_multiplier
shared_secret = tools.point_to_public_key(shared_secret_point, True)
keying_bytes = PBKDF2(shared_secret, "Bitcoin Secure Message" + nonce_pub, iterations=2048, macmodule=hmac, digestmodule=sha256).read(80)
aes_key = keying_bytes[:32]
hmac_key = keying_bytes[32:64]
aes_iv = keying_bytes[64:]
encrypter = pyaes.Encrypter(pyaes.AESModeOfOperationCFB(key=aes_key, iv=aes_iv, segment_size=16))
payload = encrypter.feed(payload) + encrypter.feed()
msg_hmac = hmac.HMAC(key=hmac_key, msg=payload, digestmod=sha256).digest()[:8]
return (nonce_pub, payload, msg_hmac)
