python如何实现DES加密
程序员文章站
2022-04-10 09:09:45
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...
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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