DES算法_granddesengt算法-优快云博客

本文链接：https://blog.youkuaiyun.com/prettyinsight/article/details/5163808

本文详细介绍了数据加密标准（DES）算法的过程，并提供了一个用C语言编写的DES算法实现示例。该示例包括密钥生成、数据加密及解密的具体步骤。

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参考资料：

1）非常详细的算法过程

http://www.tropsoft.com/strongenc/des.htm

2）用javascript写的DES，显示算法每一步的结果，对调试算法很有帮助

http://people.eku.edu/styere/Encrypt/JS-DES.html

自己用C写的算法：

/* DES算法 des.c */ #include<stdio.h> #define ENCRYPTION 1 #define DECRYPTION 0 typedef unsigned char byte; /*Permuted Choice 1*/ int PC_1[56]={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}; /*Subkey Rotattion Table*/ int SRT[16]={1,1,2,2,2,2,2,2, 1,2,2,2,2,2,2,1}; /*Permuted Choice 2*/ int PC_2[48]={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}; /*Initial Permutation*/ int IP[64]={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}; /*Inverse Initial Permutation*/ int IIP[64]={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}; /*Permutation*/ int P[32]={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}; /*E-Bit Selection Table*/ int EBST[48]={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-Box1...S-box8*/ int S[8][4][16]={ /*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}, {3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5}, {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*/ { {7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15}, {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*/ { {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*/ { {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*/ { {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} } }; /*取得key中的第n位,n>=0*/ byte getbit(byte *key,size_t n); /*设置key中的第n位为b,n>=0*/ void setbit(byte *key,size_t n,byte b); /*循环左移key一位,bits为key的位数*/ void lrotatebyonebit(byte *key,size_t bits); /*循环左移key n位,bits为key的位数*/ void lrotate(byte *key,size_t bits,size_t n); /*合并两个bits位的k1,k2到key中 k1为key中的左bits位， k2为key中的右bits位*/ void merge(byte *key,byte *k1,byte *k2,size_t bits); /*拆分2bits位的key到两个bits位的k1,k2 k1为key中的左bits位， k2为key中的右bits位*/ void split(byte *key,byte *k1,byte *k2,size_t bits); /*用size大小的table表把from置换到result中*/ void permute(byte *result,byte *from,int *table,size_t size); /*F过程 R为R[i] K为子密钥 R32存放结果*/ void F(byte *R,byte *K,byte *R32); /*des算法 text为64位数据 key为64位密钥 mode为加密或解密模式 result存放加解密后的结果*/ int des(byte *text,byte *key,int mode,byte *result); /*输出bits位的t*/ void println(byte *t,size_t bits); int main(){ /*密钥*/ byte key[8]={0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00}; /*明文*/ byte text[8]={0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF}; /*加密结果*/ byte enresult[8]; /*解密结果*/ byte deresult[8]; int i; /*加密*/ if(!des(text,key,ENCRYPTION,enresult)) return -1; println(enresult,64); /*解密*/ if(!des(enresult,key,DECRYPTION,deresult)) return -1; return 0; } int des(byte *text,byte *key,int mode,byte *result){ if(!text||!key||!result) goto Terminate_Process; if(mode!=ENCRYPTION&&mode!=DECRYPTION) goto Terminate_Process; int i,j,k,ti;/*用于循环计数*/ byte K[16][6];/*16个子密钥*/ byte fiftysixkey[7];/*临时存放56位密钥*/ byte lk[4],rk[4];/*存放28位小密钥*/ byte textp[8];/*存放置换后的数据*/ byte L[17][4],R[17][4];/*存放分割后的数据*/ byte R32[4];/*存放F过程的结果*/ byte temp[8];/*临时存放结果*/ byte row,col;/*SBox的行和列*/ /*使用Permuted Choice 1把密钥成置换56位*/ permute(fiftysixkey,key,PC_1,56); /*分割56位密钥为两个28位的小密钥*/ split(fiftysixkey,lk,rk,28); /*生成16个子密钥*/ for(i=0;i<16;i++){ /*使用Subkey Rotattion Table对两个小密钥循环左移*/ lrotate(lk,28,SRT[i]); lrotate(rk,28,SRT[i]); /*重新合并成56位密钥*/ merge(fiftysixkey,lk,rk,28); /*用Permuted Choice 2把56位密钥置换成48位*/ permute(K[i],fiftysixkey,PC_2,48); } /*使用Initial Permutation对64位数据进行置换*/ permute(textp,text,IP,64); /*分割数据*/ split(textp,L[0],R[0],32); /*16次迭代*/ for(ti=0;ti<16;ti++){ if(mode) F(R[ti],K[ti],R32); else F(R[ti],K[15-ti],R32); for(i=0;i<4;i++) R[ti+1][i]=R32[i]^L[ti][i]; memcpy(L[ti+1],R[ti],4); } /*合并成64位数据*/ merge(temp,R[16],L[16],32); /*最后使用Inverse Initial Permutation对结果进行置换*/ permute(result,temp,IIP,64); return 1; Terminate_Process: return 0; } void F(byte *R,byte *K,byte *R32){ byte temp[6]; byte B[8][1]; byte R48[6]; byte row,col; int i,j,k; /*用E-Bit Selection Table把32位的数据置换成48位*/ permute(R48,R,EBST,48); /*跟子密钥异或*/ for(i=0;i<6;i++) temp[i]=R48[i]^K[i]; /*把上一步结果分成8个6位的数据B[0]...B[7]*/ for(i=0,k=0;i<8;i++) for(j=0;j<6;j++) setbit(B[i],j,getbit(temp,k++)); /*用SBox把8个6位的数据变成8个4位的数据*/ for(i=0;i<8;i++){ row=((B[i][0] & 0x80)>>0x06)|((B[i][0] & 0x04)>>0x02); col=(B[i][0]>>0x03) & 0x0F; B[i][0]=(S[i][row][col])<<0x04; } /*把8个4位的数据组合成32位*/ for(i=0,k=0;i<8;i++) for(j=0;j<4;j++) setbit(temp,k++,getbit(B[i],j)); permute(R32,temp,P,32); } byte getbit(byte *key,size_t n){ /* n>=0 */ size_t r=n & 0x00000007; size_t d=n>>3; return ((key[d]<<r) & 0x80)>>0x07; } void setbit(byte *key,size_t n,byte b){ /* n>=0 */ size_t r=n & 0x00000007; size_t d=n>>3; if(b) key[d]|=(1<<(0x07-r)); else key[d]&= ~(1<<(0x07-r)); } void lrotatebyonebit(byte *key,size_t bits){ byte r; int i; size_t m=--bits & 0x00000007; size_t d=bits>>3; byte remainder=(key[0] & 0x80)>>0x07; key[0]<<=1; for(i=1;i<=d;i++){ r=(key[i] & 0x80)>>0x07; key[i-1]|=r; key[i]<<=1; } key[d]|=remainder<<(0x07-m); } void lrotate(byte *key,size_t bits,size_t n){ int i; for(i=0;i<n;i++) lrotatebyonebit(key,bits); } void merge(byte *key,byte *k1,byte *k2,size_t bits){ int i,j; for(i=0;i<bits;i++) setbit(key,i,getbit(k1,i)); bits<<=1; for(j=0;i<bits;i++) setbit(key,i,getbit(k2,j++)); } void split(byte *key,byte *k1,byte *k2,size_t bits){ int i,j; for(i=0;i<bits;i++) setbit(k1,i,getbit(key,i)); bits<<=1; for(j=0;i<bits;i++) setbit(k2,j++,getbit(key,i)); } void permute(byte *result,byte *from,int *table,size_t size){ int i=0; for(i=0;i<size;i++) setbit(result,i,getbit(from,table[i]-1)); } void println(byte *t,size_t bits){ int i=0; for(i=0;i<bits;i++) printf("%d",getbit(t,i)); printf("/n"); }