DES子秘钥生成算法实现

子密钥生成算法是DES加密算法中的一个重要流程，用于生成16个48位的子密钥，用于后续的轮加密操作。下面是一个简单的Python实现：

def generate_subkeys(key):
    # 生成16个48位子密钥
    pc1_table = [57, 49, 41, 33, 25, 17, 9, 1,
                 58, 50, 42, 34, 26, 18, 10, 2,
                 59, 51, 43, 35, 27, 19, 11, 3,
                 60, 52, 44, 36, 63, 55, 47, 39,
                 31, 23, 15, 7, 62, 54, 46, 38,
                 30, 22, 14, 6, 61, 53, 45, 37,
                 29, 21, 13, 5, 28, 20, 12, 4]
    pc2_table = [14, 17, 11, 24, 1, 5, 3, 28,
                 15, 6, 21, 10, 23, 19, 12, 4,
                 26, 8, 16, 7, 27, 20, 13, 2,
                 41, 52, 31, 37, 47, 55, 30, 40,
                 51, 45, 33, 48, 44, 49, 39, 56,
                 34, 53, 46, 42, 50, 36, 29, 32]
    shifts = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]
    key_bits = ''.join([f'{ord(c):08b}' for c in key])
    permuted_key = ''.join([key_bits[i - 1] for i in pc1_table])
    left_half = permuted_key[:28]
    right_half = permuted_key[28:]
    subkeys = []
    for round_num in range(1, 17):
        left_half = shift_left(left_half, round_num)
        right_half = shift_left(right_half, round_num)
        shifted_key = left_half + right_half
        subkey = ''.join([shifted_key[i - 1] for i in pc2_table])
        subkeys.append(subkey)
    return subkeys

这段代码首先将原始密钥按照表pc1_table进行置换，得到56位的密钥。然后将56位密钥分成左右两部分，每部分28位。接下来，对左右两部分分别进行16轮循环左移，并将左右两部分合并成一个56位的密钥。最后，对56位密钥再次进行置换，得到一个48位的子密钥。这样，就可以得到16个48位的子密钥，用于后续的轮加密操作。