code: public ECKey decrypt(KeyParameter aesKey) throws KeyCrypterException {
          final KeyCrypter crypter = getKeyCrypter();
          if (crypter == null)
              throw new KeyCrypterException("No key crypter available");
          return decrypt(crypter, aesKey);
      }
docs: Create a decrypted private key with AES key. Note that if the AES key is wrong, this
  has some chance of throwing KeyCrypterException due to the corrupted padding that will result, but it can also
  just yield a garbage key.
  
  @param aesKey The KeyParameter with the AES encryption key (usually constructed with keyCrypter#deriveKey and cached).