C# 腾讯云 短视频UGSV 上传签名

APP使用腾讯云的短视频（点播）上传功能，为了安全性的考虑，需要服务端进行上传签名，然后再将签名内容返回给APP，用于APP端的视频上传
下面是官方提供的签名方法

        public string GetUploadSignature()
        {
            string m_strSecId = "m_strSecId ";
            string m_strSecKey = "m_strSecKey ";
            int m_iRandom = new Random().Next(0, 1000000);
            long m_qwNowTime = GetTimeStamp();
            int m_iSignValidDuration = 3600 * 24 * 2;

            string strContent = "";
            strContent += ("secretId=" + Uri.EscapeDataString((m_strSecId)));
            strContent += ("¤tTimeStamp=" + m_qwNowTime);
            strContent += ("&expireTime=" + (m_qwNowTime + m_iSignValidDuration));
            strContent += ("&random=" + m_iRandom);

            byte[] bytesSign = hash_hmac_byte(strContent, m_strSecKey);
            byte[] byteContent = System.Text.Encoding.Default.GetBytes(strContent);
            byte[] nCon = new byte[bytesSign.Length + byteContent.Length];
            bytesSign.CopyTo(nCon, 0);
            byteContent.CopyTo(nCon, bytesSign.Length);

            return Convert.ToBase64String(nCon);
        }

其中hash_hmac_byte方法

        private byte[] hash_hmac_byte(string signatureString, string secretKey)
        {
            var enc = Encoding.UTF8; HMACSHA1 hmac = new HMACSHA1(enc.GetBytes(secretKey)); 
            hmac.Initialize();
            byte[] buffer = enc.GetBytes(signatureString);
            return hmac.ComputeHash(buffer);
        }