BSidesDC Badge

Tue, Oct 29, 2013

I recently attended my first security conference: BSidesDC. This isn’t a write up of that experience, although it was quite interesting and I learned a lot via some great sessions. One talk I really enjoyed by @grecs was Malware Analysis 101. Very well presented with lots of great getting started material.

Anyways, the badges. Pretty cool badges; bottle openers in fact, with fourteen binary bytes all with leading zeroes around the circumference: ascii encoded binary. The message is trivially found via google, but where’s the fun in that? And wanting to play around with Python some more I decided to write something that could decode the binary. My first stab looks like this.

#!/usr/bin/python
# This was a quick and dirty excercise in Python without googling the answer. 
# No error checking, etc... Check out the Python unicode page and the BitManipulation
# page for more info and probably the proper way to do this. 

import argparse

def main():

    #argparse is overkill for this, but was fun to play around with
    parser = argparse.ArgumentParser(description="Convert between ascii and binary "
                                                  and vice verse.")
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument('--to_binary', action="store", dest="ascii", nargs="+")
    group.add_argument('--to_ascii', action="store", dest="bin", nargs="+")
    args = parser.parse_args()

    #Sends user input to the appropriate function
    if args.ascii is not None:
        to_binary(args.ascii)
    elif args.bin is not None:
        to_ascii(args.bin)

def to_binary(args):
    chars_bin = [bin(ord(each)) for each in [item for sublist in args for item in \
                sublist]] 
    print " ".join([each[2:].zfill(8) for each in chars_bin])
    ### The Stack Overflow way
    ### print ''.join('{:08b}'.format(ord(each)) for each in args) 

def to_ascii(args):
    print "".join([(chr(int(str(each),2))) for each in args])
    ### The Stack Overflow way
    ### print "".join(chr(args[i:i+8],2)) for i in xrange(0, len(args), 8)) 

if __name__ == "__main__": main()

And running this with our badge’s binary:

python binary_ascii.py --to_ascii 01101001 01101110 01100010 01100101 01100101 \
01110010 01110111 01100101 01110100 01101000 01101001 01110010 01110011 01110100 
inbeerwethirst

python binary_ascii.py --to_ascii 01100010 01110011 01101001 01100100 01100101 \
01110011 01110011 01100101 01100011 01110101 01110010 01101001 01110100 01111001 
bsidessecurity

Much cleverness by the organizers. One side says “BSides Security” and the other “In Beer We Thirst”…