Signature error using Amazon Web Services SDK For PHP only when inserting encrypted data

Question

I keep getting signature errors using the AWS SDK for PHP, but it only happens I'm inserting encrypted data into SimpleDb. For example, if I comment out $userkey = "test", then I get errors, but if I leave it in, there are no errors.

    <?php
    require_once 'vendor/autoload.php';
    use Aws\Common\Aws;
    $client = Aws::factory('_loginconfig.php')->get('SimpleDb');
    $domainName = "MY_USERS_001";
    $uniqueid = uniqid();
    $userkey = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);
    //$userkey = "test";
    $name = "Bob Smith";
    try {
      $client->putAttributes(array(
        'DomainName' => $domainName,
        'ItemName'   => $uniqueid,
        'Attributes' => array(
          array('Name' => 'USER_KEY', 'Value' => $userkey, 'Replace' => true),
          array('Name' => 'USER_REALNAME', 'Value' => $name, 'Replace' => true),
        ),
      ));
    }
    catch (Aws\SimpleDb\Exception\SimpleDbException $error) {
      echo $error;
      exit;
    }
    ?>

I know nothing about encryption, hashes, signatures, so forgive me in advance for my ignorance on this.

Answer 1

After researching the issue, the solution I decided to use was to base64_encode($userkey) before I send the request.

I don't know why I am getting signature errors but this fixes the issue.