75 lines
2.0 KiB
Java
75 lines
2.0 KiB
Java
package Ciphers;
|
|
|
|
import java.math.BigInteger;
|
|
import java.security.SecureRandom;
|
|
import javax.swing.JOptionPane;
|
|
|
|
/** @author Nguyen Duy Tiep on 23-Oct-17. */
|
|
public final class RSA {
|
|
|
|
public static void main(String[] args) {
|
|
|
|
RSA rsa = new RSA(1024);
|
|
String text1 = JOptionPane.showInputDialog("Enter a message to encrypt :");
|
|
|
|
String ciphertext = rsa.encrypt(text1);
|
|
JOptionPane.showMessageDialog(null, "Your encrypted message : " + ciphertext);
|
|
|
|
JOptionPane.showMessageDialog(null, "Your message after decrypt : " + rsa.decrypt(ciphertext));
|
|
}
|
|
|
|
private BigInteger modulus, privateKey, publicKey;
|
|
|
|
public RSA(int bits) {
|
|
generateKeys(bits);
|
|
}
|
|
|
|
/**
|
|
* @return encrypted message
|
|
*/
|
|
public synchronized String encrypt(String message) {
|
|
return (new BigInteger(message.getBytes())).modPow(publicKey, modulus).toString();
|
|
}
|
|
|
|
/**
|
|
* @return encrypted message as big integer
|
|
*/
|
|
public synchronized BigInteger encrypt(BigInteger message) {
|
|
return message.modPow(publicKey, modulus);
|
|
}
|
|
|
|
/**
|
|
* @return plain message
|
|
*/
|
|
public synchronized String decrypt(String encryptedMessage) {
|
|
return new String((new BigInteger(encryptedMessage)).modPow(privateKey, modulus).toByteArray());
|
|
}
|
|
|
|
/**
|
|
* @return plain message as big integer
|
|
*/
|
|
public synchronized BigInteger decrypt(BigInteger encryptedMessage) {
|
|
return encryptedMessage.modPow(privateKey, modulus);
|
|
}
|
|
|
|
/**
|
|
* Generate a new public and private key set.
|
|
*/
|
|
public synchronized void generateKeys(int bits) {
|
|
SecureRandom r = new SecureRandom();
|
|
BigInteger p = new BigInteger(bits / 2, 100, r);
|
|
BigInteger q = new BigInteger(bits / 2, 100, r);
|
|
modulus = p.multiply(q);
|
|
|
|
BigInteger m = (p.subtract(BigInteger.ONE)).multiply(q.subtract(BigInteger.ONE));
|
|
|
|
publicKey = new BigInteger("3");
|
|
|
|
while (m.gcd(publicKey).intValue() > 1) {
|
|
publicKey = publicKey.add(new BigInteger("2"));
|
|
}
|
|
|
|
privateKey = publicKey.modInverse(m);
|
|
}
|
|
}
|