DES加密算法实现

编写DES算法实现程序，运行DES程序，演示DES加密与解密的过程。

DES算法的完整过程：

每一步实现的过程参考：DES算法过程

完整代码：

import binascii
import os
 
 
class DES():
    ip = [
        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置换表
    ip1 = [
        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
    ]  # IP逆置换表
    E = [
        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
    ]  # E扩展置换表
    P = [
        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,
    ]  # P盒置换表
    K = '0111011101101000011010010111001101101001011100110110100001110010'
    k1 = [
        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,
    ]  # 密钥初始置换表
    k2 = [
        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,
    ]
    k0 = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, ]  # 循环左移表
    S = [  # S盒的8个盒
        # 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],
    ]
 
    def replace(self, string: str, self_table: list):
        """
        :param string: 需要进行置换的列表,是一个01字符串
        :param self_table: 置换表
        """
        rep_result = ""
        for i in self_table:
            rep_result += string[i - 1]
        return rep_result
 
    def bit_encode(self, string: str):
        """
        将明文转为二进制字符串
        """
        plaintext_list = list(bytes(string, 'utf8'))  # 将字符串转成bytes类型，再转成list
        result = []
        for num in plaintext_list:
            result.append(bin(num)[2:].zfill(8))  # 将列表的每个元素转成二进制字符串，8位宽度
        return "".join(result)
 
    def str_encode(self, binary: str):
        """
        二进制字符串转成字符串
        """
        list_bin = [binary[i:i + 8] for i in range(0, len(binary), 8)]  # 对二进制字符串进行切分，每8位为一组
        list_int = []
        for b in list_bin:
            list_int.append(int(b, 2))  # 二进制转成int
        result = bytes(list_int).decode()  # 将列表转成bytes，解码，得到字符串
        return result
 
    def __bin2int(self, binary: str):
        """
        将二进制字符串每8位转成int型号列表->bytes->hex
        """
        list_bin = [binary[i:i + 8] for i in range(0, len(binary), 8)]  # 对二进制字符串进行分组，每8位为一组
        list_int = []
        for b in list_bin:
            list_int.append(int(b, 2))
        return list_int
 
    def __int2bin(self, list_int: list):
        result = []
        for num in list_int:
            result.append(bin(num)[2:].zfill(8))
        return ''.join(result)
 
    def group_by_64bit(self, binary: str):
        """
        对01字符串进行分组，64位一组，不够的在末位补0
        """
        len_binary = len(binary)
        if len_binary % 64 != 0:
            binary_block = binary + ("0" * (64 - (len_binary % 64)))
            return [binary_block[i:i + 64] for i in range(0, len(binary_block), 64)]
        else:
            return [binary[j:j + 64] for j in range(0, len(binary), 64)]
 
    def modify_default_k(self):
        """
        修改默认密钥函数
        """
        print(f'默认密钥的01字符串为：{self.K}', '  ', len(self.K), '位')
        print(f'默认密钥的字符串为：{self.str_encode(self.K)}')
        newkey = input('输入新的长度为8的密钥：')
        if len(newkey) != 8:
            print('密钥长度不合法，请重新输入：')
            self.modify_default_k()
        else:
            bin_key = self.bit_encode(newkey)
            self.K = bin_key
            print(f'当前密钥的01字符串为：{self.K}', '  ', len(self.K), '位')
 
    def f_func(self, right: str, key: str):
        """
        :param right: 明文二进制的字符串加密过程的右半部分
        :param key: 当前轮数的密钥
        """
        e_result = self.replace(right, self.E)  # E扩展置换，对right
        xor_result = self.xor_func(e_result, key)  # 与本轮子密钥key异或
        s_result = self.s_box(xor_result)  # 进行S盒压缩置换
        p_result = self.replace(s_result, self.P)  # P盒置换
        return p_result
 
    def get_key_list(self):
        key = self.replace(self.K, self.k1)
        left_key = key[0:28]
        right_key = key[28:56]
        keys = []
        for i in range(1, 17):
            move = self.k0[i - 1]
            move_left = left_key[move:28] + left_key[0:move]
            move_right = right_key[move:28] + right_key[0:move]
            left_key = move_left
            right_key = move_right
            move_key = left_key + right_key
            ki = self.replace(move_key, self.k2)
            keys.append(ki)
            # print(f'第{i}轮的子密钥为：{ki}')
        return keys
 
    def xor_func(self, xor1: str, xor2: str):
        """
        :return: 异或操作返回的结果
        """
        size = len(xor1)
        result = ""
        for i in range(0, size):
            result += '0' if xor1[i] == xor2[i] else '1'
        return result
 
    def s_box(self, xor_result: str):
        """
        :param xor_result: 48位01字符串
        :return: 48位比特串分为8组，每组6位，将6位变4位，每6位首尾做行号，其余4位做列号，在表中查找对应数值
        """
        result = ""
        for i in range(0, 8):  # 将48位数据分为6组，循环进行
            block = xor_result[i * 6:(i + 1) * 6]  # 切片
            line = int(block[0] + block[5], 2)
            colmn = int(block[1:4], 2)
            res = bin(self.S[i][line * 16 + colmn])[2:]
            if len(res) < 4:
                res = '0' * (4 - len(res)) + res
            result += res
        return result
 
    def iteration(self, bin_plaintext: str, key_list: list):
        """
        :param bin_plaintext: 待加密的64位01字符串
        :param key_list: 子密钥列表，共有16个48bit的
        """
        left = bin_plaintext[0:32]
        right = bin_plaintext[32:64]
        for i in range(0, 16):
            next_lift = right  # 本轮的right为下一轮的left
            f_result = self.f_func(right, key_list[i])
            next_right = self.xor_func(left, f_result)  # 下一轮的right由本轮的left与f函数结果异或所得
            left = next_lift
            right = next_right
            print(f'第{i + 1}轮加密/解密的结果为：{left + right}')
        bin_plaintext_result = left + right  # 准备进行下一轮
        return bin_plaintext_result[32:] + bin_plaintext_result[:32]
 
    def encode(self, plaintext):
        """
        :param plaintext: 明文字符串
        :return: 密文字符串
        """
        bin_plaintext = self.bit_encode(plaintext)
        bin_plaintext_block = self.group_by_64bit(bin_plaintext)
        ciphertext_bin_list = []
        key_list = self.get_key_list()
        for i in range(16):
            print(f'第{i + 1}轮的加密子密钥为：{key_list[i]}', '  ', len(key_list[i]), '位')
        for block in bin_plaintext_block:
            # 初代ip置换
            sub_ip = self.replace(block, self.ip)
            ite_result = self.iteration(sub_ip, key_list)
            # ip逆置换
            sub_ip1 = self.replace(ite_result, self.ip1)
            ciphertext_bin_list.append(sub_ip1)
        ciphertext_bin = ''.join(ciphertext_bin_list)
        result = self.__bin2int(ciphertext_bin)
        return bytes(result).hex().upper()
 
    def decode(self, ciphertext):
        '''
        :param ciphertext: 密文字符串
        :return: 明文字符串
        '''
        b_ciphertext = binascii.a2b_hex(ciphertext)
        bin_ciphertext = self.__int2bin(list(b_ciphertext))
        bin_plaintext_list = []
        key_list = self.get_key_list()
        key_list = key_list[::-1]
        for i in range(16):
            print(f'第{i + 1}轮的解密子密钥为：{key_list[i]}', '  ', len(key_list[i]), '位')
        bin_ciphertext_block = [bin_ciphertext[i:i + 64] for i in range(0, len(bin_ciphertext), 64)]
        for block in bin_ciphertext_block:
            sub_ip = self.replace(block, self.ip)
            ite = self.iteration(sub_ip, key_list)
            sub_ip1 = self.replace(ite, self.ip1)
            bin_plaintext_list.append(sub_ip1)
        bin_plaintext = ''.join(bin_plaintext_list).replace('00000000', '')
        return self.str_encode(bin_plaintext)
 
    def main(self):
        select = input('请选择想要进行的操作：\n1、加密\t 2、解密\t 3、退出程序\n选择：')
        if select == '1':
            plaintext = input('请输入要加密的明文：')
            ciphertext = self.encode(plaintext)
            print(f'生成的密文为：{ciphertext}')
        elif select == '2':
            plaintext = input('请输入要解密的密文：')
            plaintext = self.decode(plaintext)
            print(f'对应的明文为：{plaintext}')
            # print(len(plaintext))
        elif select == '3':
            raise SystemExit(0)  # 退出程序，返回状态码0
        else:
            input('输入不合法，请重新选择！')
            self.main()
 
 
if __name__ == '__main__':
    MyDes = DES()
    MyDes.modify_default_k()
    while True:
        MyDes.main()
        print("")
 

实验结果展示：

可以改进的地方：DES算法加密和解密的过程是一样的，因此在encode（）与decode（）两个代码块中出现了大量的重合，可以把重合的部分单独写一个公共部分的函数，在加密解密时直接调用。