网络管理及网络安全

DES 加密解密

软件1801 孙嘉成

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) FP = (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 = (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 = (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) S = [[[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]], [[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]], [[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]], [[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]], [[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]], [[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]], [[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]], [[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]]] PC_1L = (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) PC_1R = (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 = (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) 

讯享网def Permute(block, b_len, PP): # 通过置换矩阵PP对block进行置换,b_len是块长度(位，bit) res = 0 for i in PP: res = res << 1 # 第i-1的位置 即倒数第 res |= (block >> (b_len - i)) & 0x01 return res 

def bytesToblocks(m): # 字节序列转换位blocks b'\x00\x01\x02\x03\xff\xff\xff\xff' -> [0x00010203,0xffffffff] while len(m) % 8 != 0: m += b'\x00' blocks = [] for i in range(len(m) // 4): blocks.append((m[4 * i] << 24) | (m[4 * i + 1] << 16) | (m[4 * i + 2] << 8) | (m[4 * i + 3])) return blocks 

讯享网def blocksTobytes(blocks): # blocks转换为字节序列 [0x00010203,0xffffffff] -> b'\x00\x01\x02\x03\xff\xff\xff\xff' res = b'' for i in blocks: res += i.to_bytes(4, byteorder="big") return res 

L = lambda x, n: ((x << n) | (x >> (28 - n))) & 0x0fffffff # 对一个28bits的数x进行循环左移n位 

讯享网class DES(object): def F(self, block, subKeyid): temp = Permute(block, 32, E) ^ self.subKs[subKeyid] res = 0 for i in range(8): res = res << 4 yxxxxy = (temp >> 6 * (7 - i)) & 0x3f xxxx = (yxxxxy & 0x1f) >> 1 yy = ((yxxxxy >> 5) << 1) | (yxxxxy & 0x01) res |= S[i][yy][xxxx] res = Permute(res, 32, P) return res & 0xffffffff def __init__(self, K: bytes): # 通过密钥K生成实例 self.K = K self.K_blocks = bytesToblocks(K)[:2] # 生成字密钥self.subKs[16] self.subKs = None self.generate_subKs() def Encrypt(self, m: bytes) -> bytes: # 加密 blocks = bytesToblocks(m) cblocks = [] for i in range(len(blocks) // 2): # 每个64bits的高32bits，低32bits high, low = blocks[2 * i], blocks[2 * i + 1] # 第一步：初始置换IP temp = Permute((high << 32) | low, 64, IP) & 0xffffffffffffffff # 第二步：获取 Li 和 Ri high, low = temp >> 32, temp & 0xffffffff # 第三步：共16轮迭代 for j in range(16): high, low = low, (high ^ self.F(low, j)) # 第四步：合并L16和R16，注意合并为 R16L16 high, low = low, high # 第五步：末尾置换FP temp = Permute((high << 32) | low, 64, FP) & 0xffffffffffffffff high, low = temp >> 32, temp & 0xffffffff cblocks.append(high) cblocks.append(low) return blocksTobytes(cblocks) def Decrypt(self, e: bytes) -> bytes: # 解密 blocks = bytesToblocks(e) cblocks = [] for i in range(len(blocks) // 2): # 每个64bits的高32bits，低32bits high, low = blocks[2 * i], blocks[2 * i + 1] # 第一步：初始置换IP temp = Permute((high << 32) | low, 64, IP) & 0xffffffffffffffff # 第二步：获取 Li 和 Ri high, low = temp >> 32, temp & 0xffffffff # 第三步：共16轮迭代, 子密钥逆序 for j in range(16): high, low = low, (high ^ self.F(low, 15 - j)) # 第四步：合并L16和R16，注意合并为 R16L16 high, low = low, high # 第五步：末尾置换FP temp = Permute((high << 32) | low, 64, FP) & 0xffffffffffffffff high, low = temp >> 32, temp & 0xffffffff cblocks.append(high) cblocks.append(low) return blocksTobytes(cblocks) def generate_subKs(self): # print(bin((self.K_blocks[0] << 32) | self.K_blocks[1])[2:].rjust(32, '0')) C = Permute((self.K_blocks[0] << 32) | self.K_blocks[1], 64, PC_1L) & 0x0fffffff D = Permute((self.K_blocks[0] << 32) | self.K_blocks[1], 64, PC_1R) & 0x0fffffff # print(bin(C)[2:].rjust(28, '0')) # print(bin(D)[2:].rjust(28, '0')) self.subKs = [] for i in range(16): if i in (0, 1, 8, 15): C, D = L(C, 1), L(D, 1) else: C, D = L(C, 2), L(D, 2) self.subKs.append(Permute((C << 28) | D, 56, PC_2)) # print(hex(self.subKs[i])) def getK(self) -> bytes: # 返回密钥K return self.K def generateK(self) -> bytes: # 随机产生密钥K pass 

def print_bytes_hex(m): for i in m: print(hex(i)[2:].rjust(2, '0'), end='') print() 

讯享网# 密钥不足64bits 添零，多于64bits 使用前64bits # messages 不足64bits的倍数 补零 m = b'https://jwc.xauat.edu.cn' # 明文 k = b'' # 密钥  a = DES(k) cc = a.Encrypt(m) mm = a.Decrypt(cc) print("明文:", end='') print(m) print("密钥:", end='') print(a.K) print("密文:", end='') print_bytes_hex(cc) # 以bytes输出 print("解密:", end='') print(mm) 

明文:b'https://jwc.xauat.edu.cn' 密钥:b'' 密文:dfeafeea8a39fb0e46129b09c46df4016 解密:b'https://jwc.xauat.edu.cn'