DES加密算法分析实验报告

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1、中北大学软件学院信息安全技术实验报告课程名称：信息安全原理与实践实验名称：DES加密算法指导教师：学生姓名：组 号：实验日期：20160415实验地点：软件学院实验成绩：一、实验目的通过用DES算法对实际数据进行加密和解密来深刻了解DES的运行原理，进而加深对对称加密算法的理解与认识。二、实验环境1) 合天网按实验平台2) 操作系统：运行Windows ，VS2010编译环境。3) 验证软件：CAP(Cryptographic Analysis Program v4)软件，该软件位于桌面“cap4”文件夹内。三、实验内容与实验要求1) 使用cap实现DES算法的加解密2) 根据对DES算法的介

2、绍，自己创建明文信息，并选择一个密钥，编写DES密码算法的实现程序，实现加密和解密操作，并算结果将CAP4的运进行比较DES加解密算法的原理DES算法的加密流程图及参数：DES的参数： 1.密钥长度：56比特 2.输入：64比特 3.输出：64比特 4.运算轮数：16DES解密过程与加密过程完全相似，只不过将16次迭代的子密钥顺序倒过来，即 m = DES-1(c) = IP-1 T1T2.T15 T16 IP(c) 可以证明， DES-1 (DES (m) )=m使用cap实现DES算法的加解密 在“plaintext”框内输入需要加密的字符，本例输入“beijing”，在Ciphers菜单

3、中选择“des”，出现des Cipher对话框，在密钥框中输入8位密钥：“12345678”，点击“Encipher”,如下图： 可以在上图看到加密成功，在“ciphertest”框出现二进制的密文。 加密操作完成。解密操作如下：将密文复制到Ciphertext中，选择“Ciphers”菜单，选择“DES”算法，输入正确的数值产生密钥，点击“Decipher”进行解密，结果返回明文。尝试不同的值，观察返回的明文。四、实验过程与分析加密解密时主要用到的五个函数进行分析：1）初始置换表，逆初始置换表，S-Box/初始置换表IPint IP_Table64 = 57,49,41,33,25,17,

4、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, 56,48,40,32,24,16,8,0, 58,50,42,34,26,18,10,2, 60,52,44,36,28,20,12,4, 62,54,46,38,30,22,14,6;/逆初始置换表IP-1 int IP_1_Table64 = 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

5、,3,43,11,51,19,59,27, 34,2,42,10,50,18,58,26, 33,1,41,9,49,17,57,25, 32,0,40,8,48,16,56,24; /扩充置换表E int E_Table48 = 31, 0, 1, 2, 3, 4, 3,4, 5, 6, 7, 8,7,8, 9, 10,11,12,11,12,13,14,15,16,15,16,17,18,19,20,19,20,21,22,23,24,23,24,25,26,27,28,27,28,29,30,31, 0; /置换函数P int P_Table32 = 15,6,19,20,28,11,2

6、7,16,0,14,22,25, 4,17,30, 9,1, 7,23,13,31,26, 2, 8,18,12,29,5,21,10, 3,24;/S盒int S8416 =/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,

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 7,13,14,3,0,6,9,10,1,2,8,5,1

8、1,12,4,15, 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,

9、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,

10、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;/置换选择1int PC_156 = 56,48,40,32,24,16,8, 0,57,49,41,33,25,17, 9,1,58,50,42,34,26, 18,10,2,59,51,43,35, 62,54,46,38,30,22,14, 6,61,53,4

11、5,37,29,21, 13,5,60,52,44,36,28, 20,12,4,27,19,11,3;/置换选择2int PC_248 = 13,16,10,23,0,4,2,27, 14,5,20,9,22,18,11,3, 25,7,15,6,26,19,12,1, 40,51,30,36,46,54,29,39, 50,44,32,46,43,48,38,55, 33,52,45,41,49,35,28,31; /对左移次数的规定 intMOVE_TIMES16=1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1; 2）移位操作函数/字节转换成二进制int ByteToBi

12、t(ElemType ch, ElemType bit8) int cnt; for(cnt = 0;cnt cnt)&1; return 0; /二进制转换成字节int BitToByte(ElemType bit8,ElemType *ch) int cnt; for(cnt = 0;cnt 8; cnt+) *ch |= *(bit + cnt)cnt; return 0;/将长度为8的字符串转为二进制位串int Char8ToBit64(ElemType ch8,ElemType bit64) int cnt; for(cnt = 0; cnt 8; cnt+) ByteToBit(*

13、(ch+cnt),bit+(cnt3); return 0;/将二进制位串转为长度为8的字符串int Bit64ToChar8(ElemType bit64,ElemType ch8) int cnt; memset(ch,0,8); for(cnt = 0; cnt 8; cnt+) BitToByte(bit+(cnt3),ch+cnt); return 0;3）密钥相关的函数/生成子密钥int DES_MakeSubKeys(ElemType key64,ElemType subKeys1648) ElemType temp56; int cnt; DES_PC1_Transform(k

14、ey,temp); /PC1置换 for(cnt = 0; cnt 16; cnt+) /16轮跌代，产生16个子密钥 DES_ROL(temp,MOVE_TIMEScnt);/循环左移 DES_PC2_Transform(temp,subKeyscnt);/PC2置换，产生子密钥 return 0;/密钥置换1int DES_PC1_Transform(ElemType key64, ElemType tempbts56) int cnt; for(cnt = 0; cnt 56; cnt+) tempbtscnt = keyPC_1cnt; return 0;/密钥置换2int DES_P

15、C2_Transform(ElemType key56, ElemType tempbts48) int cnt; for(cnt = 0; cnt 48; cnt+) tempbtscnt = keyPC_2cnt; return 0;/循环左移int DES_ROL(ElemType data56, int time) ElemType temp56; /保存将要循环移动到右边的位 memcpy(temp,data,time); memcpy(temp+time,data+28,time); /前28位移动 memcpy(data,data+time,28-time); memcpy(da

16、ta+28-time,temp,time); /后28位移动 memcpy(data+28,data+28+time,28-time); memcpy(data+56-time,temp+time,time); return 0;4）IP置换相关函数/IP置换int DES_IP_Transform(ElemType data64) int cnt; ElemType temp64; for(cnt = 0; cnt 64; cnt+) tempcnt = dataIP_Tablecnt; memcpy(data,temp,64); return 0;/IP逆置换int DES_IP_1_Tr

17、ansform(ElemType data64) int cnt; ElemType temp64; for(cnt = 0; cnt 64; cnt+) tempcnt = dataIP_1_Tablecnt; memcpy(data,temp,64); return 0;/扩展置换int DES_E_Transform(ElemType data48) int cnt; ElemType temp48; for(cnt = 0; cnt 48; cnt+) tempcnt = dataE_Tablecnt; memcpy(data,temp,48); return 0;/P置换int DE

18、S_P_Transform(ElemType data32) int cnt; ElemType temp32; for(cnt = 0; cnt 32; cnt+) tempcnt = dataP_Tablecnt; memcpy(data,temp,32); return 0;/异或int DES_XOR(ElemType R48, ElemType L48 ,int count) int cnt; for(cnt = 0; cnt count; cnt+) Rcnt = Lcnt; return 0;/S盒置换int DES_SBOX(ElemType data48) int cnt;

19、int line,row,output; int cur1,cur2; for(cnt = 0; cnt 8; cnt+) cur1 = cnt*6; cur2 = cnt2; /计算在S盒中的行与列 line = (datacur11) + datacur1+5; row = (datacur1+13) + (datacur1+22) + (datacur1+33; datacur2+1 = (output&0X04)2; datacur2+2 = (output&0X02)1; datacur2+3 = output&0x01; return 0;/交换int DES_Swap(ElemT

20、ype left32, ElemType right32) ElemType temp32; memcpy(temp,left,32); memcpy(left,right,32); memcpy(right,temp,32); return 0; 5）加解密函数/加密单个分组int DES_EncryptBlock(ElemType plainBlock8, ElemType subKeys1648, ElemType cipherBlock8) ElemType plainBits64; ElemType copyRight48; int cnt; Char8ToBit64(plainBl

21、ock,plainBits); /初始置换（IP置换） DES_IP_Transform(plainBits); /16轮迭代 for(cnt = 0; cnt = 0; cnt-) memcpy(copyRight,cipherBits+32,32); /将右半部分进行扩展置换，从32位扩展到48位 DES_E_Transform(copyRight); /将右半部分与子密钥进行异或操作 DES_XOR(copyRight,subKeyscnt,48); /异或结果进入S盒，输出32位结果 DES_SBOX(copyRight); /P置换 DES_P_Transform(copyRight

22、); /将明文左半部分与右半部分进行异或 DES_XOR(cipherBits,copyRight,32); if(cnt != 0) /最终完成左右部的交换 DES_Swap(cipherBits,cipherBits+32); /加密文件 此函数是合天提供例子，不是DES算法关键函数，可修改。生成的文本文件，需要二进制工具打开与CAP对照intDES_Encrypt(char*plainFile,char*keyStr,char*cipherFile)FILE*plain,*cipher; intcount; ElemTypeplainBlock8,cipherBlock8,keyBloc

23、k8; ElemTypebKey64;ElemTypesubKeys1648;if(plain=fopen(plainFile,rb)=NULL) returnPLAIN_FILE_OPEN_ERROR; if(cipher=fopen(cipherFile,wb)=NULL) returnCIPHER_FILE_OPEN_ERROR; /设置密钥 memcpy(keyBlock,keyStr,8); /将密钥转换为二进制流 Char8ToBit64(keyBlock,bKey); /生成子密钥 DES_MakeSubKeys(bKey,subKeys); while(!feof(plain)

24、 /每次读8个字节，并返回成功读取的字节数 if(count=fread(plainBlock,sizeof(char),8,plain)=8) DES_EncryptBlock(plainBlock,subKeys,cipherBlock); fwrite(cipherBlock,sizeof(char),8,cipher); if(count) /填充 memset(plainBlock+count,0,7-count); /最后一个字符保存包括最后一个字符在内的所填充的字符数量 plainBlock7=8-count; DES_EncryptBlock(plainBlock,subKey

25、s,cipherBlock); fwrite(cipherBlock,sizeof(char),8,cipher); fclose(plain); fclose(cipher); returnOK; /解密文件此函数是合天提供例子，不是算法关键函数，可修改 intDES_Decrypt(char*cipherFile,char*keyStr,char*plainFile) FILE*plain,*cipher; intcount,times=0; longfileLen; ElemTypeplainBlock8,cipherBlock8,keyBlock8; ElemTypebKey64; E

26、lemTypesubKeys1648; if(cipher=fopen(cipherFile,rb)=NULL) returnCIPHER_FILE_OPEN_ERROR; if(plain=fopen(plainFile,wb)=NULL) returnPLAIN_FILE_OPEN_ERROR; /设置密钥 memcpy(keyBlock,keyStr,8); /将密钥转换为二进制流 Char8ToBit64(keyBlock,bKey); /生成子密钥 DES_MakeSubKeys(bKey,subKeys); /取文件长度 fseek(cipher,0,SEEK_END);/将文件指

27、针置尾 fileLen=ftell(cipher);/取文件指针当前位置 rewind(cipher);/将文件指针重指向文件头 while(1) /密文的字节数一定是8的整数倍 fread(cipherBlock,sizeof(char),8,cipher); DES_DecryptBlock(cipherBlock,subKeys,plainBlock); times+=8; if(timesfileLen) fwrite(plainBlock,sizeof(char),8,plain); else break; /判断末尾是否被填充 if(plainBlock78) for(count=

28、8-plainBlock7;count7;count+) if(plainBlockcount!=0) break; if(count=7)/有填充 fwrite(plainBlock,sizeof(char),8-plainBlock7,plain); else/无填充 fwrite(plainBlock,sizeof(char),8,plain); fclose(plain); fclose(cipher); returnOK; /将1.txt和kety.txt放到exe所在目录，双击exe，产生加密文件。在命令行 输入回车。输出解密文件（3.txt）intmain() DES_Encrypt(1.txt,key.txt,2.txt); system(pause); DES_Decrypt(2.txt,key.txt,3.txt); getchar(); return0; 五、心得体会1) DES需要明文合密文，才能加密和解密2) 通过本次实验，我对DES算法的加密解密原理有了一定的了解，熟悉了用DES算法对字符串和对文件进行加密。DES算法比较复杂，做加密解密实验时用DES算法来做难度有点大，一开始我还不太能理解，一定会深入学习下去。