c# .NET authentication to Ankoder API

ankoder_sample.cs

/* 
Sample Code for Ankoder API called via .NET C#
Written by William Yeung @ Gearbox Software (http://www.gearboxsoft.com)
 */
 const string PrivateKey = "YOUR_ANKODER_KEY";
var ascii = Encoding.ASCII;

var date = DateTime.Now.ToUniversalTime().ToString("ddd, dd MMM yyyy HH:mm:ss") + " GMT";
var action_url = "video.xml";
string token=string.Format("-{0}-GET-/{1}-", date, action_url);

var salt_binary = SHA1.Create().ComputeHash(ascii.GetBytes(token));
var salt=BitConverter.ToString(salt_binary).Replace("-", "").ToLower().Substring(0,20);

HMACSHA1 hmac_sha1 = new HMACSHA1(ascii.GetBytes(PrivateKey));
hmac_sha1.Initialize();

byte[] passkey_binary = hmac_sha1.ComputeHash(ascii.GetBytes(salt));

string passkey = Convert.ToBase64String(passkey_binary).Trim();

WebRequest request = WebRequest.Create(string.Format("http://api.ankoder.com/{0}", action_url));
request.Headers.Add("ankoder_access_key", AccessKey);
request.Headers.Add("ankoder_passkey",passkey);
request.Headers.Add("ankoder_date", date);
request.Method = "GET";

request.GetResponse();