python手动实现des算法

DES算法是一种对称密钥加密算法，它使用相同的密钥进行加密和解密。下面是Python手动实现DES算法的示例代码：

# DES算法实现

# IP置换矩阵
IP_table = [
    58, 50, 42, 34, 26, 18, 10, 2,
    60, 52, 44, 36, 28, 20, 12, 4,
    62, 54, 46, 38, 30, 22, 14, 6,
    64, 56, 48, 40, 32, 24, 16, 8,
    57, 49, 41, 33, 25, 17, 9, 1,
    59, 51, 43, 35, 27, 19, 11, 3,
    61, 53, 45, 37, 29, 21, 13, 5,
    63, 55, 47, 39, 31, 23, 15, 7
]

# IP逆置换矩阵
IP_inverse_table = [
    40, 8, 48, 16, 56, 24, 64, 32,
    39, 7, 47, 15, 55, 23, 63, 31,
    38, 6, 46, 14, 54, 22, 62, 30,
    37, 5, 45, 13, 53, 21, 61, 29,
    36, 4, 44, 12, 52, 20, 60, 28,
    35, 3, 43, 11, 51, 19, 59, 27,
    34, 2, 42, 10, 50, 18, 58, 26,
    33, 1, 41, 9, 49, 17, 57, 25
]

# E扩展矩阵
E_table = [
    32, 1, 2, 3, 4, 5, 4, 5,
    6, 7, 8, 9, 8, 9, 10, 11,
    12, 13, 12, 13, 14, 15, 16, 17,
    16, 17, 18, 19, 20, 21, 20, 21,
    22, 23, 24, 25, 24, 25, 26, 27,
    28, 29, 28, 29, 30, 31, 32, 1
]

# S盒子
S_box = [
    # S1
    [
        [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7],
        [0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8],
        [4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0],
        [15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13]
    ],
    # S2
    [
        [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10],
        [3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5],
        [0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15],
        [13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9]
    ],
    # S3
    [
        [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8],
        [13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1],
        [13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7],
        [1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12]
    ],
    # S4
    [
        [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15],
        [13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9],
        [10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4],
        [3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14]
    ],
    # S5
    [
        [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9],
        [14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6],
        [4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14],
        [11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3]
    ],
    # S6
    [
        [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11],
        [10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8],
        [9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6],
        [4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13]
    ],
    # S7
    [
        [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1],
        [13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6],
        [1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2],
        [6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12]
    ],
    # S8
    [
        [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7],
        [1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2],
        [7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8],
        [2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11]
    ]
]

# P置换矩阵
P_table = [
    16, 7, 20, 21,
    29, 12, 28, 17,
    1, 15, 23, 26,
    5, 18, 31, 10,
    2, 8, 24, 14,
    32, 27, 3, 9,
    19, 13, 30, 6,
    22, 11, 4, 25
]

# 置换选择1（PC-1）矩阵
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
]

# 置换选择2（PC-2）矩阵
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
]

# 左移位数表
shift_table = [
    1, 1, 2, 2, 2, 2, 2, 2,
    1, 2, 2, 2, 2, 2, 2, 1
]

# 初始密钥生成
def init_key(key):
    # 置换选择1
    key_56 = [key[PC1_table[i] - 1] for i in range(56)]

    # 循环左移
    sub_keys = [key_56]
    for i in range(16):
        sub_key = sub_keys[-1][:]
        for j in range(shift_table[i]):
            sub_key.append(sub_key.pop(0))
            sub_key[28:] = sub_key[28:]
        sub_keys.append(sub_key)

    # 置换选择2
    keys = []
    for i in range(1, 17):
        key_48 = [sub_keys[i][PC2_table[j] - 1] for j in range(48)]
        keys.append(key_48)

    return keys

# IP置换
def IP(plain_text):
    return [plain_text[IP_table[i] - 1] for i in range(64)]

# IP逆置换
def IP_inverse(cipher_text):
    return [cipher_text[IP_inverse_table[i] - 1] for i in range(64)]

# F函数
def F(R, key):
    # E扩展
    R_48 = [R[E_table[i] - 1] for i in range(48)]

    # 异或
    xor_result = [R_48[i] ^ key[i] for i in range(48)]

    # S盒子
    s_result = []
    for i in range(8):
        s_input = xor_result[i * 6:i * 6 + 6]
        s_row = (s_input[0] << 1) + s_input[-1]
        s_col = (s_input[1] << 3) + (s_input[2] << 2) + (s_input[3] << 1) + s_input[4]
        s_output = S_box[i][s_row][s_col]
        s_result.extend([(s_output >> j) & 1 for j in range(3, -1, -1)])

    # P置换
    p_result = [s_result[P_table[i] - 1] for i in range(32)]

    return p_result

# 加密函数
def encrypt(plain_text, key):
    # 初始密钥生成
    keys = init_key(key)

    # IP置换
    plain_text = IP(plain_text)

    # 分组
    L = plain_text[:32]
    R = plain_text[32:]

    # 16轮迭代
    for i in range(16):
        L, R = R, [L[j] ^ F(R, keys[i])[j] for j in range(32)]

    # 合并
    cipher_text = L + R

    # IP逆置换
    cipher_text = IP_inverse(cipher_text)

    return cipher_text

# 解密函数
def decrypt(cipher_text, key):
    # 初始密钥生成
    keys = init_key(key)

    # IP置换
    cipher_text = IP(cipher_text)

    # 分组
    L = cipher_text[:32]
    R = cipher_text[32:]

    # 16轮迭代
    for i in range(15, -1, -1):
        L, R = [R[j] ^ F(L, keys[i])[j] for j in range(32)], L

    # 合并
    plain_text = L + R

    # IP逆置换
    plain_text = IP_inverse(plain_text)

    return plain_text

需要注意的是，DES算法使用的是64位密钥，因此在实际使用中需要对密钥进行长度检查和填充等操作。此外，为了提高加密效率，也可以考虑使用其他加密算法来保护DES密钥的安全性。