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于 2020-08-02 22:09:56 发布

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分类专栏： Crypto

本文链接：https://blog.csdn.net/pondzhang/article/details/107752517

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from Crypto.Random import random
from Crypto.Util import number

def convert(m):
    m = m ^ m >> 13
    m = m ^ m << 9 & 2029229568
    m = m ^ m << 17 & 2245263360
    m = m ^ m >> 19
    return m

def transform(message):
    assert len(message) % 4 == 0
    new_message = ''
    for i in range(len(message) / 4):
        block = message[i * 4 : i * 4 +4]
        block = number.bytes_to_long(block)
        block = convert(block)
        block = number.long_to_bytes(block, 4)
        new_message += block
    return new_message

#transformed_flag = transform(flag[5:-1].decode('hex')).encode('hex')
#print 'transformed_flag:', transformed_flag
# transformed_flag: 641460a9e3953b1aaa21f3a2

transformed_flag = "641460a9e3953b1aaa21f3a2"


def decodef(flag):
    t = flag
    while 1:
        x = t
        t = transform(t)
        if (t == flag):
            return x
            break
        
print decodef(transformed_flag.decode('hex')).encode('hex')