加密流程

首先说一下置换的意思，比如说有5678这个字符串，置换表为2143，置换表中的数表示的是位置，所以字符串变成6587。所有的置换表在程序中。（S盒置换不一样，会另外说明）

密钥部分

• 把8位字符串密钥变成2进制（好像密钥只可以是8位，这一块我也没有搞太清楚）
• 64位密钥进行PC1置换，变成56位，因为以前DES是用硬件实现的，所以8，16，24，32，40，48，56，64位为校验位，不记入密钥部分。但是我们现在是用软件实现，所以这8位需要去掉，再打乱顺序。
• 将56位密钥对半分L0和R0、分别对L0和R0进行左循环移位，（当轮数为第1、2、9、16轮时，移动1位，其余时候移动两位）L0,R0移动1位后得到L1，R1。L1和R0继续进行下一轮，进行16轮。
• 上面移位得到的所以Li+Ri进行PC2置换得到16个子密钥（PC2置换把56位数据变成了48位）。
  

明文部分

• 先进行明文填充，采用PKCS #5规则，如果刚好满足每组有8个字节，则再添加一组，每个字节为000010000，如果最后一组没有8个字节，则把这一组填充成8个字节，填充的字节为少掉的字节的数目，比如有7个字节，则填充00000001。
• 再进行初始置换，把64位明文打乱。
• 进行16轮feistel函数后在进行逆初始运算
  

feistel函数

​以一组为例子来说明，一组明文8个字节，64位。有16轮迭代，要运行16次feistel函数。注意在16轮迭代前要把明文进行初始置换，迭代后把左右两边数据合并成64位再进行逆初始运算。

• 把64位明文左右对半分成两份。
• 右边的先进行部分进行扩展置换，32位变成48位。
• 再和对应轮数的子密钥进行异或运算。
• 再进行S盒运算，48位变成32位。S盒运算具体操作方法是，把48位数据分成8份，每份就有6位数据，比如010110，把头和尾结合位00，变成十进制就是0，中间四位的十进制为11，所以(x,y)为（0,11）

[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]

在上面这个表中表示的就是12，在把12变成2进制就是1100，所以6位就变成了4位。总共有8份数据，也有8个表。每份对应的运算的表都不一样。

• 再进行P盒运算。
• 最后和左边的32位进行异或运算。

解密

解密部分除了在feistel函数中调用子密钥的顺序相反外，其他都一样。加密调用的顺序是1-16，解密是16-1。

代码

#################################辅助函数####################################### 十进制转成二进制def INT_BIN(NUM): i = bin(NUM)[2:] if len(i) != 8: i = ((8 - len(i)) * '0') + i return i# 置换函数def Replace(ARR,change): ARR1 = [] for i in ARR: a = '' for j in change: a += i[j-1] ARR1.append(a) return ARR1# 异或运算def XOR(a,b): c="" for i,j in zip(a,b): if i==j: c+='0' else: c+='1' return [c]# 二进制转字符def ASCII(A): text = '' for i in A: for j in range(8): b = i[j*8:(j+1)*8] text += chr(int(b,2)) return text###############################################################################################################密钥生成####################################### 先PC1置换、将56位密钥对半分L0和R0、分别对L0和R0进行左循环移位，# （当轮数为第1、2、9、16轮时，移动1位，其余时候移动两位）L0,R0移动1位# 后得到L1，R1，L1+R0进行PC2置换得到密钥K1，L1和R0继续进行下一轮，直到生成16个子密钥# PC-1置换表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]# PC-2置换表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]# 生成子密钥函数def GenerateSubkey(Key): # 字符串转二进制 K = "" i_byte = bytes(Key, encoding='utf-8') for i_bin in i_byte: K += INT_BIN(i_bin) # PC1置换 ReplacePc1 = Replace([K],PC1) # 生成16组子密钥 Lmi = [] Rmi = [] Lmi.append(ReplacePc1[0][:28]) Rmi.append(ReplacePc1[0][28:]) for i in range(1,17): if i in (1, 2, 9, 16): Lmi.append(Lmi[i-1][1:]+Lmi[i-1][:1]) Rmi.append(Rmi[i-1][1:]+Rmi[i-1][:1]) else: Lmi.append(Lmi[i-1][2:]+Lmi[i-1][:2]) Rmi.append(Rmi[i-1][2:]+Rmi[i-1][:2]) del Lmi[0] del Rmi[0] del ReplacePc1[0] for i in range(16): ReplacePc1.append(Lmi[i]+Rmi[i]) # PC2置换 return Replace(ReplacePc1,PC2)############################################################################################################明文处理#################################### 明文填充，采用PKCS #5规则，如果刚好满足每组有8个字节，则再添加一组，每个字节为# 000010000，如果最后一组没有8个字节，则把这一组填充成8个字节，填充的字节为少掉的# 字节的数目，比如有7个字节，则填充00000001# 对明文进行填充，分组def InitPlaintext(Plaintext): DecimalList = [] BytesList = [] BinList = [] # 字符串转成10机制 i_byte = bytes(Plaintext, encoding='utf-8') for i_bin in i_byte: DecimalList.append(i_bin) # 刚好满足分组 if len(DecimalList) % 8 == 0: for i in range(8): DecimalList.append(8) for i in range(int(len(DecimalList)/8)): BytesList.append(DecimalList[i*8:(i+1)*8]) # 不满足分组 else: INT = 8 - len(DecimalList) % 8 for i in range(INT): DecimalList.append(INT) for i in range(int(len(DecimalList)/8)): BytesList.append(DecimalList[i*8:(i+1)*8]) # 10进制转2进制 for i in BytesList: TMP = '' for j in i: TMP += INT_BIN(j) BinList.append(TMP) return BinList###########################################################################################################feistel函数#################################ip初始置换表IPINIT = [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]#扩展E置换表EExten = [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]#P盒置换表PBOX = [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]#逆初始置换表P1 = [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]#8个s盒S_1 = [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] S_2 = [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] S_3 = [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] S_4 = [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] S_5 = [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] S_6 = [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] S_7 = [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] S_8 = [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]S_9 = []S_9.append(S_1)S_9.append(S_2)S_9.append(S_3)S_9.append(S_4)S_9.append(S_5)S_9.append(S_6)S_9.append(S_7)S_9.append(S_8)# S盒置换def S(R): s = '' for i in range(8): a = R[i*6:(i+1)*6] x = int(a[0]+a[-1],2) y = int(a[1:5],2) s += INT_BIN(S_9[i][x*15+y])[4:] return[s]# feistel函数def feistel(L, R, K): # 扩展置换 Expand = Replace(R,EExten) # 异或运算 Expand = XOR(Expand[0],K) # S盒运算 Expand = S(Expand[0]) # P盒 Expand = Replace(Expand,PBOX) # 异或运算 Expand = XOR(L[0],Expand[0]) return Expand[0]###########################################################################################################加、解密函数################################# 加密def Encrypt(PlanText,Key): # 初始置换 IP1 = Replace(InitPlaintext(PlanText),IPINIT) # 生成子密钥 SubkeyList = GenerateSubkey(Key) # 16轮迭代 Ciphertext = [] for i in IP1: L = i[:32] R = i[32:] for k in SubkeyList: TMP = feistel([L],[R],k) L = R R = TMP # 逆初始置换 Ciphertext.append(Replace([R+L],P1)[0]) return Ciphertext,SubkeyList# 解密def Decrypt(Ciphertext,Key): # 初始置换 IP1 = Replace(Ciphertext,IPINIT) # 16轮迭代 PlanText = [] for i in IP1: L = i[:32] R = i[32:] for k in Key[::-1]: TMP = feistel([L],[R],k) L = R R = TMP # 逆初始置换 PlanText.append(Replace([R+L],P1)[0]) return PlanText###########################################################################if __name__ == "__main__": miwen,miyao = Encrypt('computer','networks') print(miwen) print(ASCII(Decrypt(miwen,miyao)))

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