Implement RSA Algorithm Encryption and Decryption in C++.

  

• RSA (Rivest–Shamir–Adleman) is an algorithm used by modern computers to encrypt and decrypt messages. 
• It is an asymmetric cryptographic algorithm. 
• Asymmetric means that there are two different keys. 
• This is also called public key cryptography, because one of the keys can be given to anyone.

EXAMPLE :-

#include<iostream>

#include<math.h>

using namespace std;

int gcd(int a, int b) {

int s;

while(1) {

s= a%b;

if(s==0)

return b;

a = b;

b= s;

}

}

int main() {

double x = 3;

double y = 5;

double n=x*y;

double track;

double phi= (x-1)*(y-1);

double e=11;

while(e<phi) {

track = gcd(e,phi);

if(track==1)

break;

else

e++;

}

double d1=1/e;

double d=fmod(d1,phi);

double message = 13;

double c = pow(message,e);

double m = pow(c,d);

c=fmod(c,n);

m=fmod(m,n);

cout<<"Original Message = "<<message;

cout<<"\n"<<"x = "<<x;

cout<<"\n"<<"y = "<<y;

cout<<"\n"<<"n = xy = "<<n;

cout<<"\n"<<"phi = "<<phi;

cout<<"\n"<<"e = "<<e;

cout<<"\n"<<"d = "<<d;

cout<<"\n"<<"Encrypted message = "<<c;

cout<<"\n"<<"Decrypted message = "<<m;

return 0;

}

OUTPUT

Original Message = 13 x = 3 y = 5 n = xy = 15 phi = 8 e = 11 d = 0.0909091 Encrypted message = 7 Decrypted message = 13