Memo Keys

In BitShares, 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 publick 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 retreived 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 pysteem wallet to obtain keys for the corresponding accounts.

from beem.memo import Memo
from beem.account import Account

memoObj = Memo(
encrypted_memo = memoObj.encrypt(memo)

Decoding of a received memo

from getpass import getpass
from beem.block import Block
from beem.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

# Decode memo
# Raises exception if required keys not available in the wallet