byte[] expBytes = Base64.decodeBase64(exponentElem.getText().trim()));byte[] modBytes = Base64.decodeBase64(modulusElem.getText().trim());byte[] dBytes = Base64.decodeBase64(dElem.getText().trim());BigInteger modules = new BigInteger(1, modBytes);BigInteger exponent = new BigInteger(1, expBytes);BigInteger d = new BigInteger(1, dBytes);KeyFactory factory = KeyFactory.getInstance("RSA");Cipher cipher = Cipher.getInstance("RSA");String input = "test";RSAPublicKeySpec pubSpec = new RSAPublicKeySpec(modules, exponent);PublicKey pubKey = factory.generatePublic(pubSpec);cipher.init(Cipher.ENCRYPT_MODE, pubKey);byte[] encrypted = cipher.doFinal(input.getBytes("UTF-8"));System.out.println("encrypted: " + new String(encrypted));RSAPrivateKeySpec privSpec = new RSAPrivateKeySpec(modules, d);PrivateKey privKey = factory.generatePrivate(privSpec);cipher.init(Cipher.DECRYPT_MODE, privKey);byte[] decrypted = cipher.doFinal(encrypted);System.out.println("decrypted: " + new String(decrypted));