Tripwire style base64 encoding.

twb64.py

#!/usr/bin/env python3
#
# Tripwire style base64 encoding. 
# It makes sense only for 4 byte aligned sequences and is slow.
# See: https://github.com/Tripwire/tripwire-open-source/blob/master/src/fco/signature.cpp#L201
#
# Example usage for MD5 sum of files as appearing in tripwire reports:
#
#  md5sum * | python twb64.py
#

from struct import unpack
from binascii import unhexlify
from functools import reduce
import sys

twb64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

def to_twb64(data):
    bitseq_orig    = reduce(lambda x,y: x+format(y, '032b'), unpack(f'!{int(len(data) / 4)}I', data), '')
    offs           = len(bitseq_orig) % 6
    head           = [int(bitseq_orig[:offs], 2)] if offs > 0 else []
    tail_bits      = bitseq_orig[offs:]
    tail_6bit_list = [int(tail_bits[x:x+6],2) for x in range(0,len(tail_bits),6)]
    return reduce(lambda x,y: x+y, [twb64chars[x] for x in head + tail_6bit_list], '')

if __name__ == '__main__':
    for l in sys.stdin.read().splitlines():
        (h, f) = l.split()
        print(to_twb64(unhexlify(h)), f)