gistfile1.py

VALID_CHARS = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'

def cipher_string(token, pad, decipher=False):
    result = []
    for token_char, pad_char in zip(token, pad):
        token_index = VALID_CHARS.index(token_char)
        pad_index = VALID_CHARS.index(pad_char)
        if decipher:
            result_index = (token_index - pad_index) % len(VALID_CHARS)
        else:
            result_index = (token_index + pad_index) % len(VALID_CHARS)
        result.append(VALID_CHARS[result_index])
    return ''.join(result)