How to use

prependIV

method

in

org.jboss.aerogear.simplepush.util.CryptoUtil

/**
 * Encrypts the content passed-in.
 *
 * @param key the key used for the underlying cypher.
 * @param content the content to encrypted
 * @return {@code String} the encoded content as base64 url safe encoded string.
 *
 * @throws Exception
 */
public static String encrypt(final byte[] key, final String content) throws Exception {
  final byte[] iv = BlockCipher.getIV();
  final byte[] encrypted = new CryptoBox(key).encrypt(iv, content.getBytes(ASCII));
  final String base64 = new UrlBase64().encode(prependIV(encrypted, iv));
  return URLEncoder.encode(base64, ASCII.displayName());
}