rsa.cpp

实现的文件的加密解密算法

#include <iostream>
#include <fstream>
#include <cstring>
#include<string>
#include "big.h"   /* include MIRACL system */
#include "crt.h"   /* chinese remainder thereom */
using namespace std;
#define NP 2       /* two primes - could be used with more */
Miracl precision=100;
static Big pd,pl,ph;

long randise()
{ /* get a random number 得到一个随机数*/
    long seed;
    cout << "Enter 9 digit random number seed  = ";
    cin >> seed;
    return seed;
}
Big strongp(int n,long seed1,long seed2)
{ /* generate strong prime number =11 mod 12 suitable for RSA encryption */
    Big p;
    int r,r1,r2;
    irand(seed1);
    pd=rand(2*n/3,2);
    pd=nextprime(pd);
    ph=pow((Big)2,n-1)/pd;  
    pl=pow((Big)2,n-2)/pd;
    ph-=pl;
    irand(seed2);
    ph=rand(ph);
    ph+=pl;
    r1=pd%12;
    r2=ph%12;
    r=0;
    while ((r1*(r2+r))%12!=5) r++;
    ph+=r;
    do 
    { /* find p=2*r*pd+1 = 11 mod 12 */
        p=2*ph*pd+1;
        ph+=12;
    } while (!prime(p));
    return p;
}
void strip(char * name)
{ /* strip off filename extension */
    int i;
    for (i=0;name[i]!='\0';i++)
    {
        if (name[i]!='.') continue;
        name[i]='\0';
        break;
    }
}
void genkey()
{  
       int k,i;
	   //Miracl precision=100;
       long seed[2*NP];
       Big p[NP],ke;
       ofstream public_key("public.txt");
       ofstream private_key("private.txt");
       miracl *mip=&precision;
       gprime(15000);  /* speeds up large prime generation */
       do
	   {  cout << "size of each prime in bits= ";
          cin >> k;
	   } while (k<128);
	   seed[0]=randise();
       for (i=1;i<2*NP;i++)
        seed[i]=seed[i-1]+2500;
        cout << "generating keys - please wait\n";
        ke=1;
        for (i=0;i<NP;i++) 
		{ 
		   p[i]=strongp(k,seed[2*i],seed[2*i+1]);
           ke*=p[i];
		}
		cout << "加密公钥\n";
        cout << ke << endl;
        cout << "解密私钥\n";
	    for (i=0;i<NP;i++)
        cout << p[i] << endl;
         mip->IOBASE=16;
         public_key << ke << endl;    //把公钥写到文件中去
         for (i=0;i<NP;i++) 
         private_key << p[i] << endl;  //把私钥写到文件中去
}
void encode()
{
    Big e,m,y,ke,mn,mx;
    ifstream public_key("public.key");
    ifstream input_file;
    ofstream output_file;
    static char line[500];
    static char buff[256];
    static char ifname[13],ofname[13];
    BOOL fli,last;
    int i,ipt,klen;
    miracl *mip=&precision;
    mip->IOBASE=16;
    public_key >> ke;
    mn=root(ke,3);
    mx=mn*mn*mn-mn*mn;
 /* find key length in characters */
    klen=bits(mx)/7;
    cout << "file to be encoded = " ;
    cin>>ifname;
   // fli=FALSE;
    //if (strlen(ifname)>0) fli=TRUE;
    //if (fli)
   // { // set up input file 
        strcpy(ofname,ifname);
        strip(ofname);
        strcat(ofname,".rsa");
        input_file.open(ifname,ios::in); 
        /*if (!input_file)
        {
            cout << "Unable to open file " << ifname << "\n";
            //return 0;
        }*/
        cout << "encoding message\n";
    //}
    /*else
    { // accept input from keyboard 
        cout << "output filename = ";
        cin >> ofname; 
        strip(ofname);    
        strcat(ofname,".rsa");
        cout << "input message - finish with cntrl z\n";
    }*/
    output_file.open(ofname);
    ipt=0;
    last=FALSE;
    while (!last)
    { /* encode line by line */
        if (fli)
        {
            input_file.getline(&line[ipt],132);
            if (input_file.eof() || input_file.fail()) last=TRUE;
        }
        else
        {
            cin.getline(&line[ipt],132);
            if (cin.eof() || cin.fail()) last=TRUE;
        }
        strcat(line,"\n");
        ipt=strlen(line);
        if (ipt<klen && !last) continue;
        while (ipt>=klen)
        { /* chop up into klen-sized chunks and encode */
            for (i=0;i<klen;i++)
                buff[i]=line[i];
            buff[klen]='\0';
            for (i=klen;i<=ipt;i++)
                line[i-klen]=line[i];
            ipt-=klen;
            mip->IOBASE=128;
            m=buff;
            e=pow(m,3,ke);
            mip->IOBASE=16;
            output_file << e << endl;
        }
        if (last && ipt>0)
        { /* now deal with left overs */
            mip->IOBASE=128;
            m=line;
            if (m<mn)
            { /* pad out with random number if necessary */
                m+=mn*(mn*mn-rand(mn));
            }
            e=pow(m,3,ke);
            mip->IOBASE=16;
            output_file << e << endl;
        }
    }
   

}


void decode()
{
 int i;
 //Miracl precision=100;
    Big e,ep[NP],m,ke,p[NP],kp[NP],mn,mx;
    ifstream private_key("private.key");
    ifstream input_file;
    ofstream output_file;
    char ifname[13],ofname[13];
    BOOL flo;
    miracl *mip=&precision;
    mip->IOBASE=16;
    for (i=0;i<NP;i++)
    {
        private_key >> p[i];
    }
 /* construct public and private keys */
    ke=1;
    for (i=0;i<NP;i++)
    { /* Calculate ke */
        ke*=p[i];
    }
    for (i=0;i<NP;i++)
    { /* prepare for Chinese remainder thereom *
       * Find 1/3 mod p[i]-1  Euler TF         */
        kp[i]=(2*(p[i]-1)+1)/3;
    }
    mn=root(ke,3);
    mx=mn*mn*mn-mn*mn;
    do
    { /* get input file */
        cout << "file to be decoded = ";
        cin >> ifname;
    } while (strlen(ifname)==0);
    strip(ifname);
    strcat(ifname,".rsa");
    cout << "output filename = ";
    cin.sync();
    cin.getline(ofname,13);
    flo=FALSE;
    if (strlen(ofname)>0) 
    { /* set up output file */
        flo=TRUE;
        output_file.open(ofname);
    }
    cout << "decoding message\n";
    input_file.open(ifname,ios::in);
    if (!input_file)
    {
        cout << "Unable to open file " << ifname << "\n";
        
    }
    Crt chinese(NP,p);   /* use chinese remainder thereom */
    forever
    { /* decode line by line */
        mip->IOBASE=16;
        input_file >> m;
        if (m==0) break;
        for (i=0;i<NP;i++) 
            ep[i]=pow(m,kp[i],p[i]);
        e=chinese.eval(ep);
        if (e>=mx) e%=mn;
        mip->IOBASE=128;
        if (flo) output_file << e;
        cout << e << flush;
    }
    cout << "message ends\n";
}



void main()
{//mian()
  cout<<"*******************欢迎使用本加密解密应用程序**********************"<<endl;
  cout<<endl;
  cout<<endl;
  cout<<"*******************本应用程序利用的是RSA加密解密算法*************"<<endl;
  cout<<"******************请输入一个数字进入菜单进行相关操作**************"<<endl;
  cout<<"*********输入数字1:获取加密密钥和解密密钥"<<endl;
  cout<<"*********输入数字2:对文件进行加密"<<endl;
  cout<<"*********输入数字3:对文件进行解密"<<endl;
  cout<<"*********输入数字4:推出本应用程序"<<endl;
  int num;
  cin>>num;
  while(num)
  {
	   if(num==1)  
	   { genkey();
         cout<<"*********输入数字1:获取加密密钥和解密密钥"<<endl;
         cout<<"*********输入数字2:对文件进行加密"<<endl;
         cout<<"*********输入数字3:对文件进行解密"<<endl;
         cout<<"*********输入数字4:推出本应用程序"<<endl;
	     cin>>num;
	   }
	 else if(num==2)
	 {
        encode();
        cout<<"*********输入数字1:获取加密密钥和解密密钥"<<endl;
        cout<<"*********输入数字2:对文件进行加密"<<endl;
        cout<<"*********输入数字3:对文件进行解密"<<endl;
        cout<<"*********输入数字4:推出本应用程序"<<endl;
	    cin>>num;
	 }
	 else if(num==3)
	 {  decode();
        cout<<"*********输入数字1:获取加密密钥和解密密钥"<<endl;
        cout<<"*********输入数字2:对文件进行加密"<<endl;
        cout<<"*********输入数字3:对文件进行解密"<<endl;
        cout<<"*********输入数字4:推出本应用程序"<<endl;
	    cin>>num;
	 }
	 else if(num==4) 
	  { exit(0);}
			//  break;
}
//GENKEY
}