RSA.java

import java.math.BigInteger;
import java.util.*;
class RSA
{
public static void main(String args[])
{
Scanner ip=new Scanner(System.in);
int p,q,n,e=1,j;
int d=1,i1;
int t1,t2;
int pt[]= new int[10];
int ct[]= new int[10];
int rt[]= new int[10];
int temp[]= new int[10];
String i=new String();
System.out.println("Enter the two prime numbers:");
p=ip.nextInt();
q=ip.nextInt();
System.out.println("Enter the message to be sent");
i=ip.next();
i1=i.length();
n=p*q;
t1=p-1;
t2=q-1;
System.out.println("\n----------------------");
System.out.println("Sender Side:");
while((t1*t2)%e==0)
{
e++;
}
System.out.println("Public Key(e)= "+e);
System.out.println("----------------------");
for(j=0;j<i1;j++)
{
pt[j]=(i.charAt(j))-96;
//
System.out.println("Plain Text= "+pt[j]);
ct[j]=((int)Math.pow(pt[j],e))%n;
System.out.println("Cipher Text= "+ct[j]);
}
System.out.println("\nTransmitted Message:");
for(j=0;j<i1;j++)
{
temp[j]=ct[j]+96;
System.out.print((char)temp[j]);
}
System.out.println("\n\n----------------------");
System.out.println("Receiver Side:");
while((d*e)%(t1*t2)!=1)
{
d++;
}
System.out.println("Private Key(d)= "+d);
System.out.println("----------------------");
for(j=0;j<i1;j++)
{
//System.out.println("cipher Text= "+ct[j]);
BigInteger very_big_no = BigInteger.valueOf(ct[j]);
very_big_no = very_big_no.pow(d);
very_big_no = very_big_no.mod(BigInteger.valueOf(n));
rt[j] = very_big_no.intValue();
System.out.println("Plain Text= "+rt[j]);
}
System.out.println("\n----------------------");
System.out.println("Decrypted Message:");
for(j=0;j<i1;j++)
{
rt[j]=rt[j]+96;
System.out.print((char)rt[j]);
}
System.out.println("\n----------------------");
ip.close();
}
}