Vigenere密码加密、解密算法实现

//DsVigenere.cpp    穷举搜索法破解Vigenere
#include<iostream>
#include<fstream>
#include<string>
#include<cstdlib> //#include<stdlib.h>
#include<windows.h>
using namespace std;

////data structure
const int pmsize=1000;//the maximum length of the plaintext
//int i=0,j=0; //global variable
char p[pmsize]={'\0'},k[100]={'\0'},c[pmsize]={'\0'};//p,k,c memories plainrtext,ciphertext and cipher

////preparing before begining
void prepare()
{
	cout<<endl;
	cout<<"               "<<"穷举法破解Vigenere密码程序"<<endl;
	cout<<"                      "<<"设计者：刘懿"<<endl;
	cout<<"                      "<<"[2010.5.23]"<<endl;
	cout<<"==========================================================="<<endl;
	//judge whether entering the plaintext&cipher;
    char judge='Y';
	cout<<"Please sure wether you have entered the plaintext&cipher" 
		<<endl<<"with the txt form (enter Y/N):";
		cin>>judge;
	if(judge=='N'||judge=='n')
	{
		cout<<"Please enter the plaintext&cipher with the txt form Firstly!"<<endl;
		exit(1);
	}
}

////init data
void init()  
{
	//read the plaintext&cipher from txt file
	ifstream ifs1,ifs2;
	if(!ifs1||!ifs2)  //exit program if ifstream could not pen file
	{
		cerr<<"File could not be opened"<<endl;
		exit(1);
	}
	ifs1.open("plaintext1.txt");ifs1.read(p,sizeof(p));ifs1.close();
	ifs2.open("ciphertext1.txt");ifs2.read(c,sizeof(c));ifs2.close();
	cout<<"The plaintext is:"<<endl<<p<<endl;
	cout<<"The ciphertext is:"<<endl<<c<<endl;
}

////Remove spaces in the arrays p&c
void Rspace()
{
	int i=0,j=0;
	for(i=0;p[i]!='\0';i++)
	{
		if(p[i]==' ')
		{
			for(j=i;p[j+1]!='\0';j++)
				p[j]=p[j+1];
			p[j]='\0';
		}
	}
	for(i=0;c[i]!='\0';i++)
	{
		if(c[i]==' ')
		{
			for(j=i;c[j+1]!='\0';j++)
				c[j]=c[j+1];
			c[j]='\0 ';
		}
	}
}

//Crack the plaintext
void Dcipher()
{
	int number=0;
	for(int i=0;p[i]!='\0';i++) //dssolve the keys by brute force
	{
		for(int word='a';word<='z';word++)
		{
			if(c[i]==(word-'a'+(p[i]-'a'))%26+'a')
			{
				k[number]=word;
				number++;
			}
		}
	}
	for(int flag=1;flag<number;flag++) //delete the repeated cipher
		if(k[0]==k[flag])
			k[flag]='\0';
}

////output the results and delete the plaintext&cipher in the plaintext.txt&key.txt
void out()
{
	cout<<"The key is:"<<endl<<k<<endl;
	//ofstream del1("plaintext.txt",ios_base::trunc); //delete the plaintext
	//ofstream del2("key.txt",ios_base::trunc); //delete the key
}

///////////////////////////////////////////////////////////
int main()
{
	int istart,istop;  
	prepare();
	istart=GetTickCount();
	init();
	Rspace();//Remove spaces in the arrays
	Dcipher();
	out();
	istop=GetTickCount();
	cout<<"Time spent on this program(Except for the course of preparing) is "<<istop-istart<<" ms"<<endl;  
	system("pause");
	return 0;
}


密码学实验时写的代码：

//Vigenere.cpp    Vigenere密码加密
#include<iostream>
#include<fstream>
#include<string>
#include<cstdlib>
#include<windows.h>
using namespace std;

////data structure
const int pmsize=1000;//the maximum length of the plaintext
int i=0,j=0,t=0; //global variable
char p[pmsize]={'\0'},k[100]={'\0'},c[pmsize]={'\0'};//p,k,c memories plainrtext,ciphertext and cipher

////preparing before begining
void prepare()
{
	cout<<endl;
	cout<<"               "<<"Vigenere加密密码程序"<<endl;
	cout<<"                    "<<"设计者：刘懿"<<endl;
	cout<<"                    "<<"[2010.5.23]"<<endl;
	cout<<"========================================================="<<endl;
	//judge whether entering the plaintext&cipher;
    char judge='Y';
	cout<<"Please sure wether you have entered the plaintext&cipher" 
		<<endl<<"with the plaintext.txt&key.txt (enter Y/N):";
		cin>>judge;
	if(judge=='N'||judge=='n')
	{
		cout<<"Please enter the plaintext&cipher with the txt form Firstly!"<<endl;
		exit(1);
	}
}



////init data
void init()  //read the plaintext&cipher from txt file
{
	ifstream ifs1,ifs2;
	if(!ifs1||!ifs2)  //exit program if ifstream could not pen file
	{
		cerr<<"File could not be opened"<<endl;
		exit(1);
	}
	ifs1.open("plaintext.txt");ifs1.read(p,sizeof(p));ifs1.close();
	ifs2.open("key.txt");ifs2.read(k,sizeof(k));ifs2.close();
	cout<<"The plaintext is:"<<endl<<p<<endl;
}

////Remove spaces in the arrays p&k
void Rspace()
{
	for(i=0;p[i]!='\0';i++)
	{
		if(p[i]==' ')
		{
			for(j=i;p[j+1]!='\0';j++)
				p[j]=p[j+1];
			p[j]='\0';
		}
	}
	for(i=0;k[i]!='\0';i++)
	{
		if(k[i]==' ')
		{
			for(j=i;k[j+1]!='\0';j++)
				k[j]=k[j+1];
			k[j]='\0 ';
		}
	}
}

//Encrypt the plaintext
void Encrypt()
{
		for(i=0;p[i]!='\0';i++) //Encrypt the plaintext
		c[i]=(k[i%strlen(k)]-'a'+(p[i]-'a'))%26+'a';
}

////output the results and delete the plaintext&cipher in the plaintext.txt&key.txt
void out()
{
	cout<<"The ciphertext is:"<<endl<<c<<endl;
	ofstream del1("plaintext.txt",ios_base::trunc); //delete the plaintext
	ofstream del2("key.txt",ios_base::trunc); //delete the key
}

///////////////////////////////////////////////////////////
int main()
{
	int istart,istop;  
	prepare();
	istart=GetTickCount();
	init();
	Rspace();//Remove spaces in the arrays
	Encrypt();
	out();	
	istop=GetTickCount();
	cout<<"Time spent on this program(Except for the course of preparing) is "<<istop-istart<<" ms"<<endl;  
	system("pause");
	return 0;
}