DES算法Python实现源码

﹏ヽ暗。殇╰゛Y 2024-03-24 08:31 56阅读 0赞

## DES介绍 ##

DES是一种对称密钥加密算法，最初由IBM在1970年代开发。DES使用一个56位密钥和一系列置换、替换和异或操作来加密和解密数据。尽管DES被认为是一个强大的加密算法，但是由于其密钥长度较短，目前已经被认为是不安全的，并且已经被更强大的算法如AES所替代。

## 算法实现流程图 ##

### 加密算法 ###

![DES流程图][DES]

### 密钥扩展算法 ###

64位子密钥通过置换选择1、循环左移以及置换选择2，生成16个48bit的子密钥  
![密钥扩展算法][47b0dfde9926448fb16ece74321f9cb0.png]  
其中**循环左移位数与迭代的轮数相关**,第1、2、9、16轮循环左移1比特，其余循环左移2比特

## 源代码 ##

### 加密算法 ###

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_table_reverse = [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_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_boxs = [
    # 定义8个S盒
        # S1盒
        [
            [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盒
        [
            [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盒
        [
            [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盒
    [
        [ 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盒
    [
        [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盒
    [
        [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盒
    [
        [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 = [
        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
    ]
    PC1 = [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 = [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]
    
    
    def input_binary(ls, str, length):
        while True:  # input key
            s = input("please input {}(length is {} bit):".format(str, length))
            if len(s) != length:
                print("the length of {} should be {},please input again:".format(str, length))
            else:
                break;
        for c in s:
            ls.append(int(c))
    
    
    def output_ls(ls, s):
        print(s+":")
        space = 0
        for i in ls:
            print(i, end="")
            space += 1
            if space == 8:
                space = 0
                print(" ", end="")
        print("\n")
    
    
    
    
    def product_transformation(ls, k, od):
        """
    
        :param ls: 乘积变换输入
        :param k: 每一轮的轮密钥
        :param od: 判断是不是第16轮
        :return:
        """
        l = ls[0:32]
        r = ls[32:64]
        s = []
        s2 = [0]*32
        temp = []
        for i in range(0,48):                # 选择运算扩展位数
            temp.append(r[E_table[i]-1])
        temp = [a^b for a,b in zip(temp,k)]  # 结果与轮密钥k异或
        for i in range(0,8):                 # 查S盒
            index = i*6
            row =2*temp[index]+temp[index+5]
            col = 8*temp[index+1]+4*temp[index+2]+2*temp[index+3]+temp[index+4]
            s_box = S_boxs[i]
            a = s_box[row][col]
            st = bin(a)[2:]
            binary_list = [int(bit) for bit in st]
            s1=[0]*(4-len(binary_list))+binary_list
            s.extend(s1)
            # 置换运算P
        for i in range(0,32):
            s2[i] = s[P[i]-1]
            # 异或运算
        xor_list = [a ^ b for a, b in zip(l, s2)]    # 结果与Li异或
        lis = [0]*32
        for i in range(0, 32):
            lis[i] = ls[i+32]
        ls = ls[32:]+xor_list
        return ls
    
    
    def generate_round_key(ls, round_key):
        bit_num = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]
        ls1 = [0]*56
        k = [0]*48
        for i in range(0, 56):
           ls1[i] = ls[PC1[i]-1]      # PC1置换
        for i in range(0, 16):
            ls1 = ls1[bit_num[i]:28]+ls1[0:bit_num[i]]+ls1[28+bit_num[i]:]+ls1[28:28+bit_num[i]]  # 循环左移
            for j in range(0, 48):
                k[j] = ls1[PC2[j]-1] # PC2置换
            round_key.append(k.copy())
    
    
    def des_encode():
        key = [] # 0011000100110010001100110011010000110101001101100011011100111000
        M = []  #  0011000000110001001100100011001100110100001101010011011000110111
        round_key = []
        temp_list = [0]*64
        ciphertext = [0]*64
        input_binary(M, "plaintext", 64)  # 输入明文
        input_binary(key, "key", 64)        # input 密钥
    
        # sk = "0011000100110010001100110011010000110101001101100011011100111000"  # private key
        # sm = "0011000000110001001100100011001100110100001101010011011000110111"   # plaintext
        # for c in sk:
        #     key.append(int(c))
        # for c in sm:
        #         M.append(int(c))
    
        generate_round_key(key, round_key)
        for i in range(0, 64):                   # IP 置换
            temp_list[i] = M[IP_table[i]-1]
        for i in range(0, 16):
            if i != 15:
                od = 0
            else:od = 1
            temp_list=product_transformation(temp_list,round_key[i],od)   # od=1 第16轮特殊处理
        temp_list=temp_list[32:]+temp_list[0:32]
        for i in range(0, 64):
            ciphertext[i] = temp_list[IP_table_reverse[i]-1]
        output_ls(ciphertext,"ciphertext:")
    
    
    des_encode()

### 解密算法 ###

if i != 15:
                od = 0
            else: od = 1
            temp_list = product_transformation(temp_list, round_key[15-i], od)

*相应位置做替换即可*  
由于DES的运算是**对合运算**，所以加解密算法相同，只是轮密钥的使用顺序相反，即第一次迭代使用round\_key16…第16次使用round\_key1。

### 运行结果 ###

please input plaintext(length is 64 bit):0011000000110001001100100011001100110100001101010011011000110111
    please input key(length is 64 bit):0011000100110010001100110011010000110101001101100011011100111000
    ciphertext::
    10001011 10110100 01111010 00001100 11110000 10101001 01100010 01101101

[DES]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/24/1575c7223820445391f3ec867d3b9747.png
[47b0dfde9926448fb16ece74321f9cb0.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/24/a5bdf20b39a0444ab37d44f6337e4568.png