Hashed URL

gistfile1.txt

    public class HashedUrl
    {
        private readonly string _secretKey;
        private readonly string _urlToHash;
        private readonly DateTime _startDate;
        private readonly DateTime _endDate;

        /// <summary>
        /// Hash a url
        /// </summary>
        /// <param name="secretKey"> Example: 98uekjfbnw</param>
        /// <param name="urlToHash">Example: http://cdn.com/client/PRCR_1MBPS.mp4 This Url is case sensitive</param>
        /// <param name="startDate"></param>
        /// <param name="endDate"></param>
        public HashedUrl(string secretKey, string urlToHash, DateTime startDate, DateTime endDate)
        {
            _secretKey = secretKey;
            _urlToHash = urlToHash;
            _startDate = startDate;
            _endDate = endDate;
        }


        public string Generate()
        {
            var uri = new Uri(_urlToHash, UriKind.Absolute);
            var pathAndQuery = uri.PathAndQuery;
            var choppedLeftPartUrl = uri.ToString().Replace(pathAndQuery, "");
            var combinedWithParams = pathAndQuery + "?s=" + _startDate.ToString("yyyyMMddHHmmss") + "&" + "e=" + _endDate.ToString("yyyyMMddHHmmss");

            var hash = CalculateSHA1(combinedWithParams, _secretKey);
            var newPathAndQuery = combinedWithParams + "&hash=0" + hash.Substring(0, 20);
            return choppedLeftPartUrl + newPathAndQuery;
        }


        public static string CalculateSHA1(string text, string secretKey)
        {
            var textBytes = Encoding.ASCII.GetBytes(text);
            var secretKeyBytes = Encoding.ASCII.GetBytes(secretKey);

            var hmacSHA1 = new HMACSHA1(secretKeyBytes);
            var saltedHash = hmacSHA1.ComputeHash(textBytes);
            var result = ByteToString(saltedHash);
            return result.ToLower();
        }


        public static string ByteToString(byte[] buff)
        {
            var sbinary = "";
            for(var i = 0; i < buff.Length; i++)
            {
                sbinary += buff[i].ToString("X2"); // hex format
            }
            return (sbinary);
        }
    }
    
    var hashedUrl = new HashedUrl("98uekjfbnw", "http://cdn.com/client/PRCR_1MBPS.mp4", DateTime.Now, DateTime.Now.AddDays(2));