main.cpp

c++ encryption using C++

# include <iostream.h>
# include <string.h>
# include <fstream.h>
# include <math.h>
# include <stdio.h>
# include <conio.h>
# include <stdlib.h>
# define ul unsigned long
ul isPrime(ul n)
{
 ul b=1;
 for(ul i=2;i<n;i++)
  if(n%i==0) { b=0; break; }
 return b;
}
ul Power(ul x,ul y)
{
 ul ans=1;
 if(x==1) return x;
 for(ul i=1;i<=y;i++)
   ans*=x;
 return(ans);
}
char * ToBin(int x)
{
char *ans=new char[20];
int i=0;
 while(x>=1)
 {
  if(x%2==1) ans[i]='1'; else ans[i]='0';
  x/=2; i++;
 }
 if(x==1) ans[i]='1',i++;
 ans[i]='\0';
 strrev(ans);
 return(ans);
}
	ul Crypt(int x,int key,int n) // (x^y)%z //Method 2
	{
	 char *B=new char[20];
	 B=ToBin(key);
	 ul ans=1;int c=1;
	 for(int i=0;i<strlen(B);i++)
	 {
	   c=2*c;
	   ans=(ans*ans)%n;
	   if(B[i]=='1')
	   {
	    c=c+1;
	    ans=(ans*x)%n;
	   }
	 }
	 return(ans);
	}
void Fun1(int,int,int);
int Bin2Num(char *s)
{
 int ans=0; int i,j;
 for(j=0,i=7;i>=0;j++,i--)
  {
    if(s[i]=='1') ans+=Power(2,j);
  }
  return ans;
}
char * Num2Bin(int n)
{
 char *s=new char[20];
 int i=0;
 for(i=0;i<8;i++) s[i]='0';
 while(n>1)
 {
  if(n%2==1) s[i]='1';
  else s[i]='0';
  n/=2; i++;
 }
 if(n%2==1) s[i]='1'; else s[i]='0';
 s[8]='\0';
 strrev(s);
 return s;
}

void KeyEnc(int,int);
void KeyDec(int,int);
void main()
{
 clrscr();
 randomize();
  /* K E Y   G E N E R A T I O N */
 ul p,q,n,n1,e,d;
 Beg:    // Reading 2 random prime-numbers from 20 to 50
 p=2+rand()%200;
 q=2+rand()%200;
//p=17;q=11;
 if(p==q||!isPrime(p)||!isPrime(q)) goto Beg;
 n = p * q;
n1 = (p-1) * (q-1);
int x=n1+1;
 for(e=2;e<=x/2;e++)
 {
  if(x%e==0) break;
 }
  d=x/e;
 if(p==1||q==1||e==1||d==1||e==d||
 q==e||q==d||p==e||p==d) goto Beg;
// if(e>30||d>30) goto Beg;
		 ul P1=18,P2,Cypher;
B1:
 Cypher=Crypt(P1,e,n);  //Encrypting using public-key  'e'
// if(Cypher>160||Cypher<d*2||Cypher==P1) goto Beg;
 P2=Crypt(Cypher,d,n);//Decrypting using private key 'd'

 cout<<"p  	      = "<<p<<endl;
 cout<<"q             = "<<q<<endl;
 cout<<"n =(p*q)      = "<<n<<endl;
 cout<<"n1=(p-1)*(q-1)= "<<n1<<endl;
 cout<<"e	      = "<<e<<endl;
 cout<<"d	      = "<<d<<endl<<endl;
 cout<<"Public Key  : { "<<e<<","<<n<<" }"<<endl;
 cout<<"Private Key : { "<<d<<","<<n<<" }"<<endl;
cout<<"PlainText Before Encryption is : "<<P1<<endl;
cout<<"Cypher is : "<<Cypher<<endl;
cout<<"PlainText After Decryption is : "<<P2<<endl;
getch(); randomize(); clrscr();goto Beg;
// KeyEnc(e,n);
// KeyDec(d,n);
 getch();
}
void KeyEnc(int e,int n)
{
  ifstream fin("key.txt");
 ofstream fout("keyEnc.txt");
 char str[10]; int i,X,Y,j;
 //while(!fin.eof())
 for(j=0;j<8;j++)
 {
  for(i=0;i<8&&!fin.eof();i++) { fin.get(str[i]); cout<<str[i]; }
  str[8]='\0';
    cout<<str<<",";
  X=Bin2Num(str);
  Y=Crypt(X,e,n);
  cout<<X<<","<<Y<<endl;
  fout<<Y<<endl;
  getch();
 }
 fin.close(); fout.close();
}
void KeyDec(int d,int n)
{
 ifstream fin("keyEnc.txt");
 ofstream fout("keyDec.txt");
 char ch; int i,X,Y;
 char *str=new char[20];
 cout<<"Decrypt...\n";
 int Ch;
 while(!fin.eof())
 {
   fin>>Ch; if(fin.eof()) return;
   cout<<Ch;
   Y=Crypt(Ch,d,n);
   cout<<","<<Y;
   str=Num2Bin((int)Y);
   cout<<","<<str<<endl;
   fout<<str;
   getch();
 }
 fin.close(); fout.close();
}
void Fun1(int e,int d,int n)
{
 char str[30];
 cout<<"Enter some Text : ";
 gets(str);
 ofstream fout("d:\\cyfer.txt",ios::binary);
 int M,C; char ch;
 for(int i=0;i<strlen(str);i++)
 {
   C=Crypt(str[i],e,n);
   fout.put(C);
 } fout.close();
 ifstream fin("d:\\cyfer.txt");
 while(!fin.eof())
 {
    fin.get(ch);
    ch=Crypt(ch,d,n);
    cout<<ch;
 }
 fin.close();
}