using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            String authHost 
 
= "https://recognition.image.myqcloud.com/face/compare";
            uint rdm = (uint)Math.Abs(new Random().Next());
            var sign = AppSign("1251504741", "", "");
            HttpClient client = new HttpClient();
            client.DefaultRequestHeaders.Host = "recognition.image.myqcloud.com";
            client.DefaultRequestHeaders.Add(
 
"Authorization", $"Basic {sign}");
            var jsArr = new Dictionary<string, object>();
            jsArr.Add("appid", "1251504741");
            jsArr.Add("urlA", "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1547392505&di=829f4486e205b95c072970acaba924ca&imgtype=jpg&er=1&src=http%3A%2F%2Fb-ssl.duitang.com%2Fuploads%2Fitem%2F201409%2F09%2F20140909220439_myxuV.jpeg
 
");
            jsArr.Add("urlB", "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1547392532&di=9dd58cd8356f5e90eda00e53183f1a81&imgtype=jpg&er=1&src=http%3A%2F%2Fb-ssl.duitang.com%2Fuploads%2Fitem%2F201508%2F14%2F20150814165156_iAvkx.jpeg");
            HttpContent str = new StringContent(JsonConvert.SerializeObject(jsArr));
            str.Headers.Remove("Content-Type");
            str.Headers.Add("Content-Type", "application/json");
            HttpResponseMessage response = client.PostAsync(authHost, str).Result;
            String result = response.Content.ReadAsStringAsync().Result;
        }
        public static string ToHMACSHA1(string encryptText, string encryptKey)
        {
            //HMACSHA1加密
            HMACSHA1 hmacsha1 = new HMACSHA1();
            hmacsha1.Key = System.Text.Encoding.UTF8.GetBytes(encryptKey);
            byte[] dataBuffer = System.Text.Encoding.UTF8.GetBytes(encryptText);
            byte[] hashBytes = hmacsha1.ComputeHash(dataBuffer);
            return Convert.ToBase64String(hashBytes);
        }
        private static string AppSign(string appId, string secretId, string secretKey)
        {
            var ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            var currentTime = Convert.ToInt64(ts.TotalSeconds);//當前時間戳，是一個符合 UNIX Epoch 時間戳規範的數值，單位為秒，多次簽名時，e 應大於 t
            var expiredTime = Convert.ToInt64((DateTime.UtcNow.AddMinutes(180) - new DateTime(1970, 1, 1, 0, 0, 0, 0)).TotalSeconds);//簽名的有效期，是一個符合 UNIX Epoch 時間戳規範的數值，單位為秒；單次簽名時，e 必須設置為 0
            string plainText = $"a={appId}&b=&k={secretId}&e={expiredTime}&t={currentTime}&r={GetRandom()}&f=";
            return Hmacsha1Encrypt(plainText, secretKey);
        }
        /// <summary>
        /// HMACSHA1算法加密
        /// </summary>
        private static string Hmacsha1Encrypt(string encryptText, string encryptKey)
        {
            using (HMACSHA1 mac = new HMACSHA1(Encoding.UTF8.GetBytes(encryptKey)))
            {
                var hash = mac.ComputeHash(Encoding.UTF8.GetBytes(encryptText));
                var pText = Encoding.UTF8.GetBytes(encryptText);
                var all = new byte[hash.Length + pText.Length];
                Array.Copy(hash, 0, all, 0, hash.Length);
                Array.Copy(pText, 0, all, hash.Length, pText.Length);
                return Convert.ToBase64String(all);
            }
        }
        /// <summary>
        /// 獲取隨機數
        /// </summary>
        private static int GetRandom()
        {
            var random = new Random();
            var rand = random.Next(10000, 999999999);
            return rand;
        }
    }
}

騰訊人臉識別api簽名，演示demo