rsa.cpp

此文件是实现了使用rsa加密 可以加密图片、文本等

#include "rsa.h"

////////////////////*************** 产生RSA秘钥空间 **************////////////////////////////
///*** 1）生成秘钥空间
void GenerateRSAKey( )  
{
     unsigned int p, q, n,fn,e,d ; //rsa秘钥空间
	
	p = GetPrim( LENGTH );
    q = GetPrim( LENGTH );
	while(p == q)
	{
		q = GetPrim( LENGTH);
	}
	n =  p * q ;
    fn = (p-1)*(q-1);
	
	srand(time(NULL));
	do
	{
		do
		{
		  	e = rand()%(fn - 100) + 100;
			if(  e > pow(2 ,8) || e == 1)
				continue;
			if(gcd(fn,e) == 1)
				break;
		}while(1);
		d = Inverse(fn,e);
		if(d > 0)
			break;
	}while(1);
    cout<<"   秘钥空间为：   \n";
	cout <<"p " << p << endl
	   	<< "q " << q << endl
		<< "n " << n << endl
		<< "e " << e << endl
		<< "d " << d << endl;
}
///*** 2）生成素数
  unsigned int GetPrim(  unsigned int a)
{
	  unsigned int x = 0;
	while( 1 )
	{
		x = GetOdd( a );
		if(SolovayStrassen(x, 0) || SolovayStrassen((x-1)/2 , 0) )
			return x;
	}
}
///**** 3) 生成奇数
  unsigned int  GetOdd(  unsigned int a)
{
	srand(time(NULL));
	  unsigned int  x;
	while(1)
	{
		x = rand();
		if( x >= pow(2, a) && x <= pow(2,a+1) && x%2 != 0)
			return x;
	}
}
///*** 4）素性检测
bool SolovayStrassen(  unsigned int n,  unsigned int count)   
{
	if(count < 10)
	{
		  unsigned int a= rand()%(n-2) + 2;
		if(gcd(n,a) > 1)
			return true;
		else
		{
			  unsigned int JacobiValue = Jacobi(n,a);
			if(JacobiValue == -1)
				JacobiValue = n - 1;
			  unsigned int y = SquareAndMultiply( a, (n-1)/2, n);
			
			if(JacobiValue == y)
			{
				count++;
				if(!SolovayStrassen(n,count))
				{
					return false;
				}
				else
				{
					return true;
				}
			}
			else
			{
				return true;
			}			
		}
	}
	else
	{
		return false;
	}		
}

template <class T>
T Jacobi(T n, T a)  // n > a --- n is odd
{
	T state = 1;
	T temp = 0;
	
	do
	{
		if(a%2 != 0)          // if a and n are all odds...
		{
			temp = n;
			n = a;
			a = temp;         // property 4 --- swap a and n...
			
			if(((a%4 == 3) && (n%4 == 3)))
			{
				state *= -1; 	
			}
			
			a = a%n;          // property 1 --- a = a mod n...
		}            
		else if(a%2 == 0)
		{
			 unsigned int k=1;
			while((a /= 2)%2 == 0)
			{
				k++;
			}                  // property 3 --- get the exponent of 2 and the odd a...
			
			if((n%8 == 3 || n%8 == 5))
				state *= ((k%2 == 0)?1:-1);    // property 2 -- get -1 or 1 of 2/n...
		}
		
		if(a == 1)
		{
			return state;
		}
		else if(a == 2)
		{
			return (n%8 == 3 || n%8 == 5)?((-1)*state):state;
		}
	}while(1);		
}

///*** 5) 求最大公约数
  unsigned int gcd(  unsigned int a,   unsigned int b)
{
      unsigned int c; 
	for(c = a % b ; c > 0  ; c = a % b) 
	{ 
		a = b; 
		b = c; 
	} 
	return b; 
}
///*** 6) 求逆 
  unsigned int Inverse(  unsigned int a,   unsigned int b)
{
	  unsigned int a0 = a, b0 = b;
	  unsigned int t0 = 0, t = 1;
	
	  unsigned int m = a0/b0;	
	  unsigned int r = a0 - m*b0;
	
	  unsigned int temp;
	while(r > 0)
	{
		temp = t0 - m*t;
		t0 = t;
		t = temp;
		
		a0 = b0;
		b0 = r;
		
		m= a0/b0;
		
		r = a0 - m*b0;
	}
	
	do
	{
		if(t < 0)
		{
			t += a;
		}
		else
		{
			break;
		}
	}while(1);
	
	t %= a;
	
	return (b0==1)?t:0;
}

///*** 7)快速求指数
  unsigned int  SquareAndMultiply(  unsigned int BaseNum,   unsigned int exponent,   unsigned int ModN)
{
	  unsigned int result = 1;
	
	 unsigned int ExpLength = sizeof(exponent)*8;
	  unsigned int temp = 1;
	temp <<= (ExpLength-1);
	
	for( unsigned int i=0; i<ExpLength; i++)
	{
		result = (result*result)%ModN;
		result = temp & exponent ? (result*BaseNum)%ModN : result;
	    exponent <<= 1;
	}
	
	return result;
}

	
///////////*************RSA加密解密****************//////////////////////////////
///*** 1）加密
void RSAEncrypt(  unsigned int key , unsigned int n ,string filename) //key加密秘钥 filename加密文件
{
   	
      FILE *fp, *fc;
	if((fp = fopen(filename.c_str(),  "rb")) == NULL)
	{
		cout << "file "<< filename<< " open failed!" << endl;
		exit(0);
	}
	if((fc = fopen("cipher.txt", "wb")) == NULL)
	{
		cout << "file cipher.txt  write open failed!" << endl;
		exit(0);
	}
   
    unsigned char Idata;
	 unsigned int Odata;
	fread(&Idata,sizeof(unsigned char),1,fp);
	do
	{
        Odata = SquareAndMultiply(Idata,  key, n);
	
		fwrite(&Odata,4,1,fc);
		fread(&Idata,sizeof(unsigned char),1,fp);
	}while(!feof(fp));
	
	fclose(fp);
	fclose(fc);
	cout << "Encrypt end !\nThe file has been encrypted to cipher.txt" << endl;
} 
///*** 2) 解密
void RSADecrypt(  unsigned int key ,    unsigned int n , string filename) //key解密秘钥 filename加密文件
{
    FILE *fp, *fc;
	if((fp = fopen(filename.c_str(),  "rb")) == NULL)
	{
		cout << "file "<<filename <<" open failed!" << endl;
		exit(0);
	}
	if((fc = fopen("deplain.txt",  "wb")) == NULL)
	{
		cout << "file deplain.txt   open failed!" << endl;
		exit(0);
	}
   
	 unsigned int Idata;
	unsigned char Odata;
	fread(&Idata,sizeof( unsigned int),1,fp);
	do
	{
        Odata =(unsigned char)SquareAndMultiply(Idata, key, n);
		fwrite(&Odata,1,1,fc);
		fread(&Idata,sizeof( unsigned int),1,fp);
	}while(!feof(fp));
	
	fclose(fp);
	fclose(fc);
	cout << "Decrypt end !\nThe file has been decrypted to deplain.txt" << endl;
}