Cryptopals Set 1 Walkthrough - Challenge 1

The Challenge

The first challenge involves converting the following hex string to base64:

49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d

The result should be:

SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t

With an important clue of “Always operate on raw bytes, never on encoded strings.” Which of course I didn’t comprehend until after using b'' and I even used .encode(utf-8). When I used either function it did not convert the string to raw bytes it just added a b’ in front of the string b"49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d". I got a different output when I switched to the bytes.fromhex() method after a few minutes on StackOverflow and Python Doc page on the method.

>>> bytes.fromhex('49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d')
b"I'm killing your brain like a poisonous mushroom"

Now we’re getting somewhere! After that I slapped together this piece of code:

import base64

hex_str = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d"

byte_str = bytes.fromhex(hex_str)  # b"I'm killing your brain like a poisonous mushroom"
base64_str = base64.b64encode(byte_str)  # {bytes} b'SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t'
ascii_string = base64_str.decode("ASCII")  # {str} 'SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t'
print(ascii_string)