RSA

public class RSAUtil {
    private static final int KEY_SIZE = 2048;

    public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(KEY_SIZE, SecureRandom.getInstanceStrong());
        return keyPairGen.generateKeyPair();
    }

    public static String encrypt(String plainText, PublicKey publicKey) 
            throws Exception {
        Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return Base64.getEncoder().encodeToString(
            cipher.doFinal(plainText.getBytes())
        );
    }

    public static String decrypt(String cipherText, PrivateKey privateKey) 
            throws Exception {
        Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return new String(cipher.doFinal(
            Base64.getDecoder().decode(cipherText)
        ));
    }
}