#include<iostream>
#include<cmath>
#include<cstring>
using namespace std;
unsigned char k[8],temptable[30000],plaintable[30000],nowtable[30000],sonkey[30000] ; int  plainlength,klength;
int ktable[256],stable[256];
class rc4
{
  public:
	  static unsigned char xor(unsigned char a,unsigned char b);    //加解密的時候進行異或運算，注意要轉換成unsigned char類型，否則異或會出現大于255的現象
	  static void swap( int *a, int *b);   //兩個數進行交換操作
	  static void KSA();      //密鑰調度
	  static void PRGA();     //偽隨機生成
	  void cryption();         //加密
	  void decryption();      //解密
	  void dtoh(unsigned char a);   //轉換成16進制輸出
	  rc4() {};   //構造函數

};

unsigned char rc4::xor(unsigned char a,unsigned char b)
{
	return a^b;
}


void rc4::swap( int *a, int *b)
{
    int temp;
	temp=*a;
	*a=*b;
	*b=temp;
}

void rc4::KSA()
{
	int i,j=0;
	for(i=0;i<256;i++)
	{
		j=(j+stable[i]+( int)ktable[i])%256;
		swap(&stable[i],&stable[j]);
	}
	cout<<endl;
	cout<<"************************"<<endl;
	cout<<"Output Key"<<endl;
    for(i=0;i<256;i++)
		cout<<stable[i]<<" ";
	cout<<endl;

}

void rc4::PRGA()
{
    int m=0,i=0,j=0,t,l;l=plainlength;
	while(l--)     //密鑰長度要和明文長度一致
	{
		i=(i+1)%256;
		j=(j+stable[i])%256;
		swap(&stable[i],&stable[j]);
		t=(stable[j]+stable[i])%256;
		sonkey[m++]=stable[t];               //將子密鑰存放在sonkey數組中
	}
	
}

void rc4::cryption()
{
	KSA();
	PRGA();
	for(int i=0;i<plainlength;i++)
		temptable[i]=xor(plaintable[i],sonkey[i]); //將明文和密鑰異或運算

}

void rc4::decryption()
{
	for(int i=0;i<plainlength;i++)
		nowtable[i]=xor(temptable[i],sonkey[i]);   //將密文和密鑰異或運算
}
void rc4::dtoh(unsigned char a)
{   
	    int high,low;
	//	cout<<(int)a<<"  ";   
	   low=a%16;
		high=(int)a/16; 
    	if(high>=10) cout<<(char)(high+55);       //大于10的或要裝換成相應的字符形式
		else cout<<high;
		if(low>=10) cout<<(char)(low+55)<<" ";
			else cout<<low<<" ";  
      
	
	

}

int main()
{    
	 rc4 *RC;RC=new rc4();
     int i,j;
	 for(i=0;i<256;i++)      //初始s數據表
		 stable[i]=i;
	  cout<<"Input Key"<<endl;
      
	  cin.getline((char*)k,9);
	  klength=strlen((char*)k);
	  cout<<"********************************"<<endl;
	  cout<<"Input PlainText"<<endl;
	  

	  cin.getline((char*)plaintable,30000);
      plainlength=strlen((char*)plaintable);
	  for(i=0,j=0;i<256;i++)
	  { 
		  ktable[i]=k[j++];      //初始k數據表
		  j%=klength;
	  }
	  RC->cryption();         //加密
	  cout<<"***********************"<<endl;
      cout<<"CipherText"<<endl;
	  for(i=0;i<plainlength;i++)
		  RC->dtoh(temptable[i]);   //裝換成116進制輸出
	  cout<<endl;
	  cout<<"***********************"<<endl;
	  cout<<"Decryption"<<endl;
      RC->decryption();       //解密
	  for(i=0;i<plainlength;i++)
		  cout<<plaintable[i];

	  return 0;
	  


      
}