Android hamc 算法，知道进来帮帮忙 =======================

[-船长-]

这是服务器 HMAC的算法，我不知道怎么在Android实现。

/**
 * Calculate the HMAC for the http request.
 * This function signs an api request using the information provided. The signature returned
 * has been base64 encoded and then url encoded.
 *
 * @param string $algo          The HMAC algorithm used
 * @param string $time          String representation of unix time
 * @param string $nonce         Nonce
 * @param string $api_key       Your api key
 * @param string $secret_key    Your private key
 * @param string $get_variables URLEncoded string representation of the get variable parameters,
 *                              eg "method=user&guid=2"
 * @param string $post_hash     Optional sha1 hash of the post data.
 *
 * @return string The HMAC signature
 * @access private
 */
function calculate_hmac($algo, $time, $nonce, $api_key, $secret_key,
$get_variables, $post_hash = "") {

	global $CONFIG;

	elgg_log("HMAC Parts: $algo, $time, $api_key, $secret_key, $get_variables, $post_hash");

	$ctx = hash_init(map_api_hash($algo), HASH_HMAC, $secret_key);

	hash_update($ctx, trim($time));
	hash_update($ctx, trim($nonce));
	hash_update($ctx, trim($api_key));
	hash_update($ctx, trim($get_variables));
	if (trim($post_hash) != "") {
		hash_update($ctx, trim($post_hash));
	}

	return urlencode(base64_encode(hash_final($ctx, true)));
}

这是我实现的方法，但是就是通过不了服务器的验证：

try {
			MessageDigest sha1 = MessageDigest.getInstance("SHA-1");
			sha1.update(EncodingUtils.getAsciiBytes(PUBLIC_API_KEY));
			sha1.update(EncodingUtils.getAsciiBytes(time));
			sha1.update(EncodingUtils.getAsciiBytes(nonce));
			sha1.update(EncodingUtils.getAsciiBytes(PRIVATE_API_KEY));
			hmac = new String(Base64.encode(sha1.digest(), 0));
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

[-船长-]

有人解释一下PHP服务端是怎么实现的吗 ？