code: public static InputStream decrypt(InputStream inputStream, byte[] key) {
          checkNotNull(inputStream);
          checkNotNull(key);
          AESFastEngine aesEngine = new AESFastEngine();
          PaddedBufferedBlockCipher cipher =
                  new PaddedBufferedBlockCipher(aesEngine, new PKCS7Padding());
          cipher.init(false, new KeyParameter(key));
          return new CipherInputStream(inputStream, cipher);
      }
docs: AES/ECB/PKCS5Padding Decryption
  
  @param inputStream input stream to be decrypted
  @param key         valid AES key sizes are 128, 192, or 256 bits (16, 24, or 32 bytes).
  @return decrypted input stream