编程实现DES算法。 加密学号和班级

为了实现DES算法，需要先了解DES算法的基本步骤和流程。DES算法是一种对称加密算法，它的基本步骤包括：

1. 密钥的生成
2. 初始置换IP
3. 16轮Feistel加密
4. 逆置换IP^-1

在实现DES算法时，需要用到一些常数和表格，包括：

1. 初始置换IP表
2. 逆置换IP^-1表
3. 扩展置换E表
4. S盒
5. P盒

以下是Python实现DES算法的代码：

# 导入必要的模块
import binascii

# 定义常数和表格

# 初始置换IP表
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
]

# 逆置换IP^-1表
IP_INV_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
]

# 扩展置换E表
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
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盒
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
]

# 密钥的生成
def generate_keys(key):
    # 将密钥转换为二进制格式
    key = binascii.unhexlify(key)
    # 将密钥进行初始置换
    key = permute(key, IP_TABLE)
    # 将密钥分为左右两部分
    left = key[:28]
    right = key[28:]
    keys = []
    for i in range(16):
        # 根据移位表进行循环左移
        left = left[SHIFT_TABLE[i]:] + left[:SHIFT_TABLE[i]]
        right = right[SHIFT_TABLE[i]:] + right[:SHIFT_TABLE[i]]
        # 将左右两部分合并
        sub_key = left + right
        # 根据压缩表进行压缩
        sub_key = permute(sub_key, COMPRESS_TABLE)
        keys.append(sub_key)
    return keys

# 对消息进行加密
def encrypt(message, key):
    # 将消息转换为二进制格式
    message = binascii.unhexlify(message)
    # 将消息进行初始置换
    message = permute(message, IP_TABLE)
    # 将消息分为左右两部分
    left = message[:32]
    right = message[32:]
    # 生成子密钥
    keys = generate_keys(key)
    for i in range(16):
        # 将右半部分进行扩展置换
        expanded = permute(right, E_TABLE)
        # 将扩展后的右半部分和子密钥进行异或
        xor_result = xor(expanded, keys[i])
        # 将异或后的结果进行S盒置换
        s_result = s_box_substitution(xor_result)
        # 将S盒置换后的结果进行P盒置换
        p_result = permute(s_result, P_TABLE)
        # 将P盒置换后的结果和左半部分进行异或
        xor_result = xor(p_result, left)
        # 将左右两部分交换
        left = right
        right = xor_result
    # 将左右两部分合并
    result = right + left
    # 将合并后的结果进行逆置换
    result = permute(result, IP_INV_TABLE)
    # 将结果转换为十六进制格式
    result = binascii.hexlify(result)
    return result

# 对消息进行解密
def decrypt(message, key):
    # 将消息转换为二进制格式
    message = binascii.unhexlify(message)
    # 将消息进行初始置换
    message = permute(message, IP_TABLE)
    # 将消息分为左右两部分
    left = message[:32]
    right = message[32:]
    # 生成子密钥
    keys = generate_keys(key)
    for i in range(15, -1, -1):
        # 将右半部分进行扩展置换
        expanded = permute(right, E_TABLE)
        # 将扩展后的右半部分和子密钥进行异或
        xor_result = xor(expanded, keys[i])
        # 将异或后的结果进行S盒置换
        s_result = s_box_substitution(xor_result)
        # 将S盒置换后的结果进行P盒置换
        p_result = permute(s_result, P_TABLE)
        # 将P盒置换后的结果和左半部分进行异或
        xor_result = xor(p_result, left)
        # 将左右两部分交换
        left = right
        right = xor_result
    # 将左右两部分合并
    result = right + left
    # 将合并后的结果进行逆置换
    result = permute(result, IP_INV_TABLE)
    # 将结果转换为十六进制格式
    result = binascii.hexlify(result)
    return result

# 二进制字符串进行置换
def permute(data, table):
    result = bytearray(len(table) // 8)
    for i, pos in enumerate(table):
        byte_pos = pos - 1
        byte_index = byte_pos // 8
        bit_pos = byte_pos % 8
        byte = data[byte_index]
        if byte & (1 << (7 - bit_pos)):
            result[i // 8] |= 1 << (7 - i % 8)
    return bytes(result)

# 二进制字符串进行异或
def xor(data1, data2):
    result = bytearray(len(data1))
    for i in range(len(data1)):
        result[i] = data1[i] ^ data2[i]
    return bytes(result)

# S盒置换
def s_box_substitution(data):
    result = bytearray(len(data) // 6)
    for i in range(len(result)):
        byte = data[i*6:(i+1)*6]
        row = (byte[0] << 1) + byte[-1]
        col = (byte[1] << 3) + (byte[2] << 2) + (byte[3] << 1) + byte[4]
        value = S_BOX[i][row][col]
        for j in range(4):
            if value & (1 << (3 - j)):
                result[i] |= 1 << (4 * (i+1) - (j+1))
    return bytes(result)

# 测试代码
if __name__ == '__main__':
    # 加密学号和班级
    message = '317010XXXX'
    key = '0123456789ABCDEF'
    encrypted = encrypt(message, key)
    print('加密后的结果：', encrypted)
    decrypted = decrypt(encrypted, key)
    print('解密后的结果：', decrypted)

需要注意的是，由于Python中的字节串和二进制串不同，因此在实现DES算法时需要注意对字节串和二进制串的转换。在代码中，我们使用了`binascii.unhexlify`和`binascii.hexlify`函数将十六进制字符串转换为字节串和二进制串。另外，为了方便测试，我们在代码中使用了固定的密钥和消息，实际使用时应该根据具体情况动