攻防世界 misc Exercise 刷题记录

1、base64stego

1、zip伪加密
2、base64文件隐写，在网上找一个脚本

def get_base64_diff_value(s1, s2):
    base64chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
    res = 0
    for i in xrange(len(s1)):
        if s1[i] != s2[i]:
            return abs(base64chars.index(s1[i]) - base64chars.index(s2[i]))
    return res
def solve_stego():
    with open('stego.txt', 'rb') as f:
        file_lines = f.readlines()
    bin_str = ''
    for line in file_lines:
        steg_line = line.replace('\n', '')
        norm_line = line.replace('\n', '').decode('base64').encode('base64').replace('\n', '')
        diff = get_base64_diff_value(steg_line, norm_line)
        pads_num = steg_line.count('=')
        if diff:
            bin_str += bin(diff)[2:].zfill(pads_num * 2)
        else:
            bin_str += '0' * pads_num * 2
    res_str = ''
    for i in xrange(0, len(bin_str), 8):
        res_str += chr(int(bin_str[i:i+8], 2))
    print res_str
solve_stego()