package com.thealgorithms.ciphers;
import java.math.BigInteger;
import java.security.SecureRandom;
public class RSA {
private BigInteger modulus;
private BigInteger privateKey;
private BigInteger publicKey;
public RSA(int bits) {
generateKeys(bits);
}
public synchronized String encrypt(String message) {
return (new BigInteger(message.getBytes())).modPow(publicKey, modulus).toString();
}
public synchronized BigInteger encrypt(BigInteger message) {
return message.modPow(publicKey, modulus);
}
public synchronized String decrypt(String encryptedMessage) {
return new String((new BigInteger(encryptedMessage)).modPow(privateKey, modulus).toByteArray());
}
public synchronized BigInteger decrypt(BigInteger encryptedMessage) {
return encryptedMessage.modPow(privateKey, modulus);
}
public final 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 = BigInteger.valueOf(3L);
while (m.gcd(publicKey).intValue() > 1) {
publicKey = publicKey.add(BigInteger.TWO);
}
privateKey = publicKey.modInverse(m);
}
}