Question

Is RSA algorithm is same as Ceaser Cipher Algorithm?

if not kindly make simple program of RSA in c and c++.

Answer 1

RSA algorithm and Ceaser cipher both are different.

RSA algorithm follows Asymmetric encryption where as Ceaser Cipher follows Symmetric encryption.

Symmetric encryption is a type of encryption where only one key (a secret key) is used to both encrypt & decrypt the data(electronic information).

Asymmetric encryption uses two keys(public key and private key) to encrypt a plain text. A public key(first key) is made freely available to anyone who might want to send you a message. The second private key is kept a secret so that you can only know.

program for RSA in c++:-

#include<iostream>
#include<math.h>
using namespace std;

int GCD(int a, int b) {
int t;
while(1) {
t= a%b;
if(t==0)
return b;
a = b;
b= t;
}
}
int main() {
//take 2 random prime numbers
double p = 13;
double q = 11;
double n=p*q;//calculate product of given 2 prime numbers.
double track;
double phi= (p-1)*(q-1);//calculate phi
double enc=7;//e is used for encrypt
//for checking that 1 < e < phi(n) and gcd(e, phi(n)) = 1; i.e., e and phi(n) are coprime.
while(enc<phi) {
track = GCD(enc,phi);
if(track==1)
break;
else
enc++;
}
//choosing d such that it satisfies d*e = 1 mod phi
double d1=1/enc;
double dec=fmod(d1,phi);//d is used for decrypt
double message = 9;
double c = pow(message,enc); //encrypt the message
double m = pow(c,dec);
c=fmod(c,n);
m=fmod(m,n);
cout<<"Original Message = "<<message;
cout<<"\n"<<"p = "<<p;
cout<<"\n"<<"q = "<<q;
cout<<"\n"<<"n = pq = "<<n;
cout<<"\n"<<"phi = "<<phi;
cout<<"\n"<<"e = "<<enc;
cout<<"\n"<<"d = "<<dec;
cout<<"\n"<<"Encrypted message = "<<c;
cout<<"\n"<<"Decrypted message = "<<m;
return 0;
}

program for RSA in C:-

#include<stdio.h>
#include<math.h>
int GCD(int a, int b) {
int t;
while(1) {
t= a%b;
if(t==0)
return b;
a = b;
b= t;
}
}
int main() {
//take 2 random prime numbers
double p = 13;
double q = 11;
double n=p*q;//calculate product of given 2 prime numbers.
double track;
double phi= (p-1)*(q-1);//calculate phi
double enc=7;//e is used for encrypt
//for checking that 1 < e < phi(n) and gcd(e, phi(n)) = 1; i.e., e and phi(n) are coprime.
while(enc<phi) {
track = GCD(enc,phi);
if(track==1)
break;
else
enc++;
}
//choosing d such that it satisfies d*e = 1 mod phi
double d1=1/enc;
double dec=fmod(d1,phi);//d is used for decrypt
double message = 9;
double c = pow(message,enc); //encrypt the message
double m = pow(c,dec);
c=fmod(c,n);
m=fmod(m,n);
//all double values are adjusted to 3 decimal points.
printf("Original Message = %.3lf",message);
printf("\n p=%.3lf ",p);
printf("\n q=%.3lf ",q);
printf("\n n=%.3lf ",n);
printf("\n phi=%.3lf ",phi);
printf("\n enc=%.3lf ",enc);
printf("\n dec=%.3lf ",dec);
printf("\n encrypted messag=%.3lf ",c);
printf("\n decrypted message=%.3lf ",m);
return 0;
}