The RSA algorithm can be used for both public key encryption and digital signatures. Its security is based on the difficulty of factoring large integers.
The RSA algorithm’s efficiency requires a fast method for performing the modular exponentiation operation. A less efficient, conventional method includes raising a number (the input) to a power (the secret or public key of the algorithm, denoted e and d, respectively) and taking the remainder of the division with N. A straight-forward implementation performs these two steps of the operation sequentially: first, raise it to the power and second, apply modulo
Source Code:
import java.util.*;
import java.io.*;
public class rsa
{ static int gcd(int m,int n)
{ while(n!=0)
{ int r=m%n;
m=n;
n=r;
}
return m;
}
public static void main(String args[])
{
int p=0,q=0,n=0,e=0,d=0,phi=0;
int nummes[]=new int[100];
int encrypted[]=new int[100];
int decrypted[]=new int[100];
int i=0,j=0,nofelem=0;
Scanner sc=new Scanner(System.in);
String message ;
System.out.println("Enter the Message tobe encrypted:");
message= sc.nextLine();
System.out.println("Enter value of p and q\n");
p=sc.nextInt();
q=sc.nextInt();
n=p*q;
phi=(p-1)*(q-1);
for(i=2;i
if(gcd(i,phi)==1) break;
e=i;
for(i=2;i
if((e*i-1)%phi==0)
break;
d=i;
for(i=0;i
{
char c = message.charAt(i);
int a =(int)c;
nummes[i]=c-96;
}
nofelem=message.length();
for(i=0;i
{
encrypted[i]=1;
for(j=0;j
encrypted[i] =(encrypted[i]*nummes[i])%n;
}
System.out.println("\n Encrypted message\n");
for(i=0;i
{
System.out.print(encrypted[i]);
System.out.print((char)(encrypted[i]+96));
}
for(i=0;i
{ decrypted[i]=1;
for(j=0;j
decrypted[i]=(decrypted[i]*encrypted[i])%n;
}
System.out.println("\n Decrypted message\n ");
for(i=0;i
System.out.print((char)(decrypted[i]+96));
return;
}
}
******************************************************** Enter the text: hello Enter the value of P and Q : 5 7 Encrypted Text is: 8 h 10 j 17 q 17 q 15 o Decrypted Text is: hello