这里写目录标题
移位密码
概述
以 z 26 运算为例 , k 为密钥 加密： e k ( x ) = ( x + k ) m o d 26 解密： d k ( x ) = ( x − k ) m o d 26 以z_{26} 运算为例,k为密钥 \\加密：e_k(x)=(x+k) mod 26 \\解密：d_k(x)=(x-k) mod 26 以z26运算为例,k为密钥加密：ek(x)=(x+k)mod26解密：dk(x)=(x−k)mod26
实际中，我们使用 Z 256 Z_{256} Z256运算（群的加法运算）
代码
cpp
#include <iostream>
#include <fstream>
#include<cstring>
using namespace std;
int main(){
//加密写入
ofstream fileOut;
char helloTxt[]{"&9*&((@#$)((%#^^hello,world!\n123456789"};
int txtLen{strlen(helloTxt)};
fileOut.open("hello.data",ios::binary);
int k=77;
for(int i=0;i<txtLen;i++){
fileOut<<char((helloTxt[i]+k) %256);
}
fileOut.close();
//解密读出
ifstream fileIn;
char helloChar;
fileIn.open("hello.data",ios::binary);
while (fileIn.get(helloChar)){
cout<<char((helloChar-k) %256);
}
fileIn.close();
}
bash
&9*&((@#$)((%#^^hello,world!
123456789
Process returned 0 (0x0) execution time : 0.120 s
Press any key to continue.希尔密码( Z 256 Z_{256} Z256)
待加密长度被3整除
cpp
#include <iostream>
#include <fstream>
#include<cstring>
#include "e:/eigen/Eigen/Dense"
using namespace std;
using namespace Eigen;
int main(){
//加密写入
ofstream fileOut;
char helloTxt[]{"123456789$#%(&Yoiu9"};
int txtLen{strlen(helloTxt)};
fileOut.open("hello.data",ios::binary);
for(int i=0;i<txtLen;i+=3){
Matrix<int,1,3> x{helloTxt[i],helloTxt[i+1],helloTxt[i+2]};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
fileOut.close();
//解密读出
ifstream fileIn;
char helloChar;
fileIn.open("hello.data",ios::binary);
char txtBuffer[4];
for(int i=0;i<txtLen;i+=3){
fileIn.read(txtBuffer,3);
Matrix<int,1,3> y{txtBuffer[0],txtBuffer[1],txtBuffer[2]};
Matrix<int,3,3> k_ni{{9,11, 227},{101 ,152 ,37},{134 ,248 ,127}};
Matrix<int,1,3> e_data=y*k_ni;
for (int j=0;j<3;j++){
cout<<char(int(e_data[j]) % 256);
}
}
fileIn.close();
}待加密长度不一定被3整除
继续完善程序，针对加密长度不一定是3的倍数。
cpp
#include <iostream>
#include <fstream>
#include<cstring>
#include "e:/eigen/Eigen/Dense"
using namespace std;
using namespace Eigen;
int main(){
//加密写入
ofstream fileOut;
char helloTxt[]{"123456789p"};
int txtLen{strlen(helloTxt)};
fileOut.open("hello.data",ios::binary);
for(int i=0;i<txtLen;i+=3){
if ((txtLen-i)==1){
Matrix<int,1,3> x{helloTxt[i],0,0};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
else if ((txtLen-i)==2){
Matrix<int,1,3> x{helloTxt[i],helloTxt[i+1],0};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
else{
Matrix<int,1,3> x{helloTxt[i],helloTxt[i+1],helloTxt[i+2]};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
}
fileOut.close();
//解密读出
ifstream fileIn;
char helloChar;
fileIn.open("hello.data",ios::binary);
char txtBuffer[4];
for(int i=0;i<txtLen;i+=3){
fileIn.read(txtBuffer,3);
Matrix<int,1,3> y{txtBuffer[0],txtBuffer[1],txtBuffer[2]};
Matrix<int,3,3> k_ni{{9,11, 227},{101 ,152 ,37},{134 ,248 ,127}};
Matrix<int,1,3> e_data=y*k_ni;
char d_data[3];
for (int j=0;j<3;j++){
d_data[j]=char(int(e_data[j]) % 256);
}
if ((txtLen-i)==2 ){
cout<<d_data[0]<<d_data[1];
}
else if((txtLen-i)==1 ){
cout<<d_data[0];
}
else{
for (int j=0;j<3;j++){
cout<<d_data[j];
}
}
}
fileIn.close();
}
bash
123456789p
Process returned 0 (0x0) execution time : 0.376 s
Press any key to continue.加解密文件
cpp
#include <iostream>
#include <fstream>
#include<cstring>
#include "e:/eigen/Eigen/Dense"
using namespace std;
using namespace Eigen;
int main(){
//加密写入
ifstream picfs("test.png", ios::ate|ios::binary);
// 获取文件大小
std::streampos picSize = picfs.tellg();
picfs.close(); // 关闭文件
std::cout << "文件长度: " << picSize << " 字节" << std::endl;
ifstream ifs("test.png", ios::in|ios::binary);
char *picData=new char[picSize+1];
for (int i=0;i<picSize;i++){
ifs.get(picData[i]);
}
ifs.close();
int txtLen{picSize};
ofstream fileOut;
fileOut.open("pic.dat",ios::binary);
for(int i=0;i<txtLen;i+=3){
if ((txtLen-i)==1){
Matrix<int,1,3> x{picData[i],0,0};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
else if ((txtLen-i)==2){
Matrix<int,1,3> x{picData[i],picData[i+1],0};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
else{
Matrix<int,1,3> x{picData[i],picData[i+1],picData[i+2]};
Matrix<int,3,3> k{{16,91,215}, {171,253,50}, {8,186,121}};
Matrix<int,1,3> e_data=x*k;
for (int j=0;j<3;j++){
fileOut<<char(int(e_data[j]) % 256);
}
}
}
fileOut.close();
//解密读出
ofstream deFileOut;
deFileOut.open("test_d.png",ios::binary);
ifstream fileIn;
char helloChar;
fileIn.open("pic.dat",ios::binary);
char txtBuffer[4];
for(int i=0;i<txtLen;i+=3){
fileIn.read(txtBuffer,3);
Matrix<int,1,3> y{txtBuffer[0],txtBuffer[1],txtBuffer[2]};
Matrix<int,3,3> k_ni{{9,11, 227},{101 ,152 ,37},{134 ,248 ,127}};
Matrix<int,1,3> e_data=y*k_ni;
char d_data[3];
for (int j=0;j<3;j++){
d_data[j]=char(int(e_data[j]) % 256);
}
if ((txtLen-i)==2 ){
deFileOut<<d_data[0]<<d_data[1];
}
else if((txtLen-i)==1 ){
deFileOut<<d_data[0];
}
else{
for (int j=0;j<3;j++){
deFileOut<<d_data[j];
}
}
}
deFileOut.close();
fileIn.close();
delete[] picData;
}