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DES，全称Data Encryption Standard，是1970年代由IBM开发的一种对称加密算法，后来被美国国家标准局（NIST）采纳为联邦信息处理标准（FIPS）。DES在密码学领域具有重要的历史地位，是现代块加密算法的鼻祖之一。 DES算法基于Feistel结构，它将明文分为64位的数据块，并使用56位的密钥进行加密。这个56位密钥实际上是从64位密钥中通过移位操作提取出来的，因为8位用于奇偶校验，不参与实际的加密过程。DES加密过程包含16轮迭代，每轮迭代都有不同的子密钥应用，这些子密钥是从主密钥通过一系列复杂的键扩展过程生成的。在每一轮迭代中，DES算法执行以下四个主要步骤： 1. **子密钥产生**：从主密钥中提取出48位的子密钥，每轮使用一个不同的子密钥。 2. **异或操作**：将当前数据块与子密钥进行异或运算。 3. **置换函数P**：将异或后的结果通过一个固定的置换表进行重新排列。 4. **S盒操作**：将经过置换后的数据分成8个6位的部分，分别通过8个不同的S盒（Substitution Box），S盒将6位输入转化为4位输出，这一过程结合了非线性变换，增加了破解的难度。解密过程与加密过程基本相反，使用相同的16个子密钥，但应用的顺序和操作相反：先进行逆S盒操作，然后逆置换，最后与子密钥异或。尽管DES在当时是一种强大的加密算法，但随着计算能力的提升，其56位的密钥长度已不再安全，因为现代计算机可以快速尝试所有可能的密钥组合。因此，DES现在通常只作为教学用途，实际应用中更倾向于使用它的加强版——3DES（Triple DES），或者更先进的AES（Advanced Encryption Standard）。在"DES算法.cpp"这个文件中，很可能是实现了DES算法的C++源代码。这通常包括了上述步骤的函数定义，如键扩展、轮函数等，以及整个加密和解密过程的主函数。通过阅读和理解这段代码，你可以深入学习DES算法的内部工作原理，了解如何在实际程序中应用密码学技术。 DES算法是密码学中至关重要的一部分，它为后续的块加密算法提供了基础框架。虽然现在已经被更安全的算法所替代，但了解DES可以帮助我们理解现代密码学的发展历程，以及对称加密的基本概念。

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DES算法.cpp 9KB

#include <windows.h> DWORDLONG dwlKey_PC_1[64]= { 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, 21,13,5,28,20,12,4,0}; DWORDLONG dwlKey_PC_2[64]={ 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, 46,42,50,36,29,32,0}; DWORDLONG dwlData_IP[65]={ 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, 63,55,47,39,31,23,15,7,0}; DWORDLONG dwlData_Expansion[64]={ 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, 28,29,30,31,32,1,0}; DWORDLONG dwlData_P[33]={ 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, 22,11,4,25,0}; DWORDLONG dwlData_FP[65]={ 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, 33,1,41,9,49,17,57,25,0}; DWORDLONG OS[512]={//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 }; //des.cpp #include <stdio.h> #include <string.h> #include <windows.h> #include <conio.h> #include "Schedle.h" class CShift{ public: DWORDLONG mask[16]; int step[16]; CShift(){ for(int i=0;i<16;i++){ step[i]=2; mask[i]=0xc000000; } step[0]=step[1]=step[8]=step[15]=1; mask[0]=mask[1]=mask[8]=mask[15]=0x8000000; } }; class CDES{ public: CDES(){ m_dwlKey=0; m_dwlData=0; ConvertTableToMask(dwlKey_PC_1,64); //PrintTable(dwlKey_PC_1,7,8); ConvertTableToMask(dwlKey_PC_2,56); ConvertTableToMask(dwlData_IP,64); ConvertTableToMask(dwlData_Expansion,32); ConvertTableToMask(dwlData_FP,64); ConvertTableToMask(dwlData_P,32); Generate_S(); } void PrintBit(DWORDLONG); void EncryptKey(char *); unsigned char* EncryptData(unsigned char *); unsigned char* DescryptData(unsigned char*); private: void ConvertTableToMask(DWORDLONG *,int); void Generate_S(void); void PrintTable(DWORDLONG*,int,int); DWORDLONG ProcessByte(unsigned char*,BOOL); DWORDLONG PermuteTable(DWORDLONG,DWORDLONG*,int); void Generate_K(void); void EncryptKernel(void); DWORDLONG Generate_B(DWORDLONG,DWORDLONG*); /*For verify schedule permutation only*/ DWORDLONG UnPermuteTable(DWORDLONG,DWORDLONG*,int); DWORDLONG dwlData_S[9][4][16]; CShift m_shift; DWORDLONG m_dwlKey; DWORDLONG m_dwlData; DWORDLONG m_dwl_K[17]; }; void CDES::EncryptKey(char *key){ printf("\nOriginal Key: %s",key); m_dwlKey=ProcessByte((unsigned char*)key,TRUE); m_dwlKey=PermuteTable(m_dwlKey,dwlKey_PC_1,56); Generate_K(); } void CDES::Generate_K(void){ DWORDLONG C[17],D[17],tmp; C[0]=m_dwlKey>>28; D[0]=m_dwlKey&0xfffffff; for(int i=1;i<=16;i++){ tmp=(C[i-1]&m_shift.mask[i-1])>>(28-m_shift.step[i-1]); C[i]=((C[i-1]<<m_shift.step[i-1])|tmp)&0x0fffffff; tmp=(D[i-1]&m_shift.mask[i-1])>>(28-m_shift.step[i-1]); D[i]=((D[i-1]<<m_shift.step[i-1])|tmp)&0x0fffffff; m_dwl_K[i]=(C[i]<<28)|D[i]; m_dwl_K[i]=PermuteTable(m_dwl_K[i],dwlKey_PC_2,48); } } DWORDLONG CDES::ProcessByte(unsigned char *key,BOOL shift){ unsigned char tmp; DWORDLONG byte=0; int i=0; while(i<8){ while(*key){ if(byte!=0) byte<<=8; tmp=*key; if(shift) tmp<<=1; byte|=tmp; i++; key++; } if(i<8) byte<<=8; i++; } return byte; } DWORDLONG CDES::PermuteTable(DWORDLONG dwlPara,DWORDLONG* dwlTable,int nDestLen){ int i=0; DWORDLONG tmp=0,moveBit; while(i<nDestLen){ moveBit=1; if(dwlTable[i]&dwlPara){ moveBit<<=nDestLen-i-1; tmp|=moveBit; } i++; } return tmp; } DWORDLONG CDES::UnPermuteTable(DWORDLONG dwlPara,DWORDLONG* dwlTable,int nDestLen){ DWORDLONG tmp=0; int i=nDestLen-1; while(dwlPara!=0){ if(dwlPara&0x01) tmp|=dwlTable[i]; dwlPara>>=1; i--; } return tmp; } void CDES::PrintTable(DWORDLONG *dwlPara,int col,int row){ int i,j; for(i=0;i<row;i++){ printf("\n"); getch(); for(j=0;j<col;j++) PrintBit(dwlPara[i*col+j]); } } void CDES::PrintBit(DWORDLONG bitstream){ char out[76]; int i=0,j=0,space=0; while(bitstream!=0){ if(bitstream&0x01) out[i++]='1'; else out[i++]='0'; j++; if(j%8==0){ out[i++]=' '; space++; } bitstream=bitstream>>1; } out[i]='\0'; strcpy(out,strrev(out)); printf("%s **:%d\n",out,i-space); } void CDES::ConvertTableToMask(DWORDLONG *mask,int max){ int i=0; DWORDLONG nBit=1; while(mask[i]!=0){ nBit=1; nBit<<=max-mask[i]; mask[i++]=nBit; } } void CDES::Generate_S(void){ int i; int j,m,n; m=n=0; j=1; for(i=0;i<512;i++){ dwlData_S[j][m][n]=OS[i]; n=(n+1)%16; if(!n){ m=(m+1)%4; if(!m) j++; } } } unsigned char * CDES::EncryptData(unsigned char *block){ unsigned char *EncrytedData=new unsigned char(15); printf("\nOriginal Data: %s\n",block); m_dwlData=ProcessByte(block,0); m_dwlData=PermuteTable(m_dwlData,dwlData_IP,64); EncryptKernel(); DWORDLONG bit6=m_dwlData; for(int i=0;i<11;i++){ EncrytedData[7-i]=(unsigned char)(bit6&0x3f)+46; bit6>>=6; } EncrytedData[11]='\0'; printf("\nAfter Encrypted: %s",EncrytedData); for(i=0;i<8;i++){ EncrytedData[7-i]=(unsigned char)(m_dwlData&0xff); m_dwlData>>=8; } EncrytedData[8]='\0'; return EncrytedData; } void CDES::EncryptKernel(void){ int i=1; DWORDLONG L[17],R[17],B[9],EK,PSB; L[0]=m_dwlData>>32; R[0]=m_dwlData&0xffffffff; for(i=1;i<=16;i++){ L[i]=R[i-1]; R[i-1]=PermuteTable(R[i-1],dwlData_Expansion,48); //Expansion R EK=R[i-1]^m_dwl_K[i]; //E Permutation PSB=Generate_B(EK,B); //P Permutation R[i]=L[i-1]^PSB; } R[16]<<=32; m_dwlData=R[16]|L[16]; m_dwlData=PermuteTable(m_dwlData,dwlData_FP,64); } unsigned char* CDES::DescryptData(unsigned char *desData){ int i=1; unsigned char *DescryptedData=new unsigned char(15); DWORDLONG L[17],R[17],B[9],EK,PSB; DWORDLONG dataPara; dataPara=ProcessByte(desData,0); dataPara=PermuteTable(dataPara,dwlData_IP,64); R[16]=dataPara>>32; L[16]=dataPara&0xffffffff; for(i=16;i>=1;i--){ R[i-1]=L[i]; L[i]=PermuteTable(L[i],dwlData_Expansion,48); //Expansion L EK=L[i]^m_dwl_K[i]; //E Permutation PSB=Generate_B(EK,B); //P Permutation L[i-1]=R[i]^PSB; } L[0]<<=32; dataPara=L[0]|R[0];