Salt transcoding

salt_transcoding.py

import string
import base64

# bcrypt uses a strange base64 encoding, which is incompatible with the common one, go figure...
B64_CHARS = ''.join((string.ascii_uppercase, string.ascii_lowercase, string.digits, '+/')).encode("utf-8")
B64_CHARS_BCRYPT = ''.join(('./', string.ascii_uppercase, string.ascii_lowercase, string.digits)).encode("UTF-8")

B64_TO_BCRYPT = bytes.maketrans(B64_CHARS, B64_CHARS_BCRYPT)
B64_FROM_BCRYPT = bytes.maketrans(B64_CHARS_BCRYPT, B64_CHARS)


def decode_b64(data):
    return base64.b64encode(data).translate(B64_TO_BCRYPT, b'=')


def translate_salt(rounds: int, salt: bytes) -> bytes:
    return b"$" + b"2b" + b"$" + ("%2.2u" % rounds).encode("ascii") + b"$" + decode_b64(salt)


if __name__ == '__main__':
    print(translate_salt(10, b"abcdefghabcdefgh").decode("utf-8"))