code: public static String encrypt(byte[] key256Bits, String plainText) {
          SecretKey secretKey = new SecretKeySpec(key256Bits, "AES");
          return encryptBouncyCastle(secretKey, plainText);
  //        return encryptLegacyJavaSecurity(secretKey, plainText);
      }
docs: Encrypt the plain text.
  
  @param key256Bits
  256 bit key
  @param plainText
  text that needs to be encrypted
  @return the iv as a hex string followed by '$' followed by the encrypted text.