RSACipher.java

/*
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 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package week03;
import java.math.BigInteger;
import java.util.Random;
/**
 *
 * @author levan
 */
public class RSACipher {
    private BigInteger p,q,N,r,E,D;
    private int bitLength;
    public  RSACipher(int bitLength){
        this.bitLength = bitLength;
        generateKeys();
    }
    private void generateKeys(){
        p=BigInteger.probablePrime(bitLength / 2, new Random());
        q=BigInteger.probablePrime(bitLength / 2, new Random());
        N=p.multiply(q);
        r= p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
        do{
            E = new BigInteger(bitLength, new Random());
        }while ((E.compareTo(r) != -1)|| (E.gcd(r).compareTo(BigInteger.ONE) !=0));
        D = E.modInverse(r);    
    }
    public BigInteger[] encrypt (String message){
        byte[] bytes= message.getBytes();
        BigInteger[ ]encrypted = new BigInteger[bytes.length];
        for (int i=0; i<bytes.length;i++){
            encrypted[i]= new BigInteger(new byte []{bytes[i]}).modPow(E, N);
        }
        return encrypted;
        
        
    }
    public String decrypt(BigInteger[] message, BigInteger d, BigInteger n){
        byte[] bytes = new byte[message.length];
        for(int i=0;i<message.length;i++){
            bytes[i] = message[i].modPow(d, n).byteValue();
        }
        return new String(bytes);
        
    }
    public BigInteger getP(){
        return p;
    }
   public BigInteger getQ(){
        return q;
    }
   public BigInteger getN(){
        return N;
    }
   public BigInteger getE(){
        return E;
    }
   public BigInteger getD(){
        return D;
    }
}