bhive.memo module

class bhive.memo.Memo(from_account=None, to_account=None, hive_instance=None)

Bases: object

Deals with Memos that are attached to a transfer

Parameters
  • from_account (Account) – Account that has sent the memo

  • to_account (Account) – Account that has received the memo

  • hive_instance (Hive) – Hive instance

A memo is encrypted with a shared secret derived from a private key of the sender and a public key of the receiver. Due to the underlying mathematics, the same shared secret can be derived by the private key of the receiver and the public key of the sender. The encrypted message is perturbed by a nonce that is part of the transmitted message.

from bhive.memo import Memo
m = Memo("hiveeu", "wallet.xeroc")
m.hive.wallet.unlock("secret")
enc = (m.encrypt("foobar"))
print(enc)
>> {'nonce': '17329630356955254641', 'message': '8563e2bb2976e0217806d642901a2855'}
print(m.decrypt(enc))
>> foobar

To decrypt a memo, simply use

from bhive.memo import Memo
m = Memo()
m.hive.wallet.unlock("secret")
print(m.decrypt(op_data["memo"]))

if op_data being the payload of a transfer operation.

Memo Keys

In Hive, memos are AES-256 encrypted with a shared secret between sender and receiver. It is derived from the memo private key of the sender and the memo public key of the receiver.

In order for the receiver to decode the memo, the shared secret has to be derived from the receiver’s private key and the senders public key.

The memo public key is part of the account and can be retrieved with the get_account call:

get_account <accountname>
{
  [...]
  "options": {
    "memo_key": "GPH5TPTziKkLexhVKsQKtSpo4bAv5RnB8oXcG4sMHEwCcTf3r7dqE",
    [...]
  },
  [...]
}

while the memo private key can be dumped with dump_private_keys

Memo Message

The take the following form:

{
  "from": "GPH5mgup8evDqMnT86L7scVebRYDC2fwAWmygPEUL43LjstQegYCC",
  "to": "GPH5Ar4j53kFWuEZQ9XhxbAja4YXMPJ2EnUg5QcrdeMFYUNMMNJbe",
  "nonce": "13043867485137706821",
  "message": "d55524c37320920844ca83bb20c8d008"
}

The fields from and to contain the memo public key of sender and receiver. The nonce is a random integer that is used for the seed of the AES encryption of the message.

Encrypting a memo

The high level memo class makes use of the bhive wallet to obtain keys for the corresponding accounts.

from bhive.memo import Memo
from bhive.account import Account

memoObj = Memo(
    from_account=Account(from_account),
    to_account=Account(to_account)
)
encrypted_memo = memoObj.encrypt(memo)

Decoding of a received memo

from getpass import getpass
from bhive.block import Block
from bhive.memo import Memo

# Obtain a transfer from the blockchain
block = Block(23755086)                   # block
transaction = block["transactions"][3]    # transactions
op = transaction["operations"][0]         # operation
op_id = op[0]                             # operation type
op_data = op[1]                           # operation payload

# Instantiate Memo for decoding
memo = Memo()

# Unlock wallet
memo.unlock_wallet(getpass())

# Decode memo
# Raises exception if required keys not available in the wallet
print(memo.decrypt(op_data["transfer"]))
decrypt(memo)

Decrypt a memo

Parameters

memo (str) – encrypted memo message

Returns

encrypted memo

Return type

str

encrypt(memo, bts_encrypt=False)

Encrypt a memo

Parameters

memo (str) – clear text memo message

Returns

encrypted memo

Return type

str

unlock_wallet(*args, **kwargs)

Unlock the library internal wallet