RsaCipher.java

public class RsaCipher {

    private PublicKey publicKey;
    private PrivateKey privateKey;

    public RsaCipher(PublicKey publicKey, PrivateKey privateKey) {
        this.publicKey = publicKey;
        this.privateKey = privateKey;
    }

    public static KeyPair genKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(512);
        KeyPair keyPair = generator.generateKeyPair();

        return keyPair;
    }

    public String encrypt(String string) throws InvalidKeyException, NoSuchPaddingException, NoSuchAlgorithmException, BadPaddingException, IllegalBlockSizeException {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return new String(cipher.doFinal(string.getBytes()));
    }

    public String decrypt(String string) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, IOException, BadPaddingException, IllegalBlockSizeException {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return new String(cipher.doFinal(string.getBytes()));
    }
}