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SHA-256实现的输出不正确

  •  0
  • user2508324  · 技术社区  · 8 年前

    对于个人项目,我正在Python 3中实现SHA-256,而不使用 hashlib 模块(因为这会破坏学习SHA-256工作原理的目的)。我一直在 Wikipedia pseudocode ,但我的代码给出了错误的输出(与 哈希库 输出)。我盯着代码看了一个小时,除了头痛之外,我还没有发现自己做错了什么。

    代码:

    #!/usr/bin/env python3
    
    import hashlib
    import sys
    
    # ror function taken from http://stackoverflow.com/a/27229191/2508324
    def ror(val, r_bits, max_bits=32):
        return ((val & (2**max_bits-1)) >> r_bits%max_bits)|(val << (max_bits-(r_bits%max_bits)) & (2**max_bits-1))
    
    h = [0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19]
    
    k = [0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
       0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
       0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
       0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
       0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
       0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
       0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
       0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2]
    
    s = sys.stdin.read().encode()
    msg = [int(x,2) for c in s for x in '{:08b}'.format(c)]
    msg.append(1)
    while len(msg) % 512 != 448:
        msg.append(0)
    msg.extend([int(x,2) for x in '{:064b}'.format(len(s))])
    
    for i in range(len(msg)//512):
        chunk = msg[512*i:512*(i+1)] # sloth love chunk
        w = [0 for _ in range(64)]
        for j in range(16):
            w[j] = int(''.join(str(x) for x in chunk[32*j:32*(j+1)]),2)
        for j in range(16, 64):
            s0 = ror(w[j-15], 7) ^ ror(w[j-15], 18) ^ (w[j-15] >> 3)
            s1 = ror(w[j-2], 17) ^ ror(w[j-2], 19) ^ (w[j-2] >> 10)
            w[j] = (w[j-16] + s0 + w[j-7] + s1) % 2**32
        work = h[:]
        for j in range(64):
            S1 = ror(work[4], 6) ^ ror(work[4], 11) ^ ror(work[4], 25)
            ch = (work[4] & work[5]) ^ (~work[4] & work[6])
            temp1 = (work[7] + S1 + ch + k[j] + w[j]) % 2**32
            S0 = ror(work[0], 2) ^ ror(work[0], 13) ^ ror(work[0], 22)
            maj = (work[0] & work[1]) ^ (work[0] & work[2]) ^ (work[1] & work[2])
            temp2 = (S0 + maj) % 2**32
            work = [(temp1 + temp2) % 2**32] + work[:-1]
            work[4] = (work[4] + temp1) % 2**32
        h = [(H+W)%2**32 for H,W in zip(h,work)]
    
    print(''.join('{:08x}'.format(H) for H in h))
    print(hashlib.sha256(s).hexdigest())
    

    如果实现正确,两个输出将匹配。相反,我得到了这个(输入 abc ):

    $ echo -n abc | ./sha256.py
    203b1d9016060802fe5ef80436611159de1868b58d44940e3d3979eab5f4d193
    ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad
    

    我已经彻底检查了代码,但我看不出它与维基百科伪代码有什么区别。我怀疑错误在压缩循环中( for j in range(64): ). 我已经通过初始化 w 数组,它全部检出。

    任何帮助都将不胜感激!

    1 回复  |  直到 8 年前
        1
  •  0
  •   phihag    8 年前

    SHA1工作在位上,而不是字节上。因此,填充末尾的64位长度也用位表示;错误就在这条线上

    msg.extend([int(x,2) for x in '{:064b}'.format(len(s))])
    

    应该是

    msg.extend([int(x,2) for x in '{:064b}'.format(len(s) * 8)])