短信验证码

代码源自 Microsoft.AspNet.Identity 程序集.

using System;
using System.Net;
using System.Security.Cryptography;
using System.Text;

namespace Authentication
{
    internal static class Rfc6238AuthenticationService
    {
        private static readonly DateTime _unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        private static readonly TimeSpan _timestep = TimeSpan.FromMinutes(3.0);
        private static readonly Encoding _encoding = new UTF8Encoding(false, true);

        private static int ComputeTotp(HashAlgorithm hashAlgorithm, ulong timestepNumber, string modifier)
        {
            byte[] bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder((long)timestepNumber));
            byte[] array = hashAlgorithm.ComputeHash(ApplyModifier(bytes, modifier));
            int num = (int)(array[array.Length - 1] & 15);
            int num2 = (int)(array[num] & 127) << 24 | (int)(array[num + 1] & 255) << 16 |
                       (int)(array[num + 2] & 255) << 8 | (int)(array[num + 3] & 255);
            return num2 % 1000000;
        }

        private static byte[] ApplyModifier(byte[] input, string modifier)
        {
            if (string.IsNullOrEmpty(modifier))
            {
                return input;
            }
            byte[] bytes = _encoding.GetBytes(modifier);
            byte[] array = new byte[checked(input.Length + bytes.Length)];
            Buffer.BlockCopy(input, 0, array, 0, input.Length);
            Buffer.BlockCopy(bytes, 0, array, input.Length, bytes.Length);
            return array;
        }

        private static ulong GetCurrentTimeStepNumber()
        {
            return
                (ulong)
                    ((DateTime.UtcNow - _unixEpoch).Ticks /
                     _timestep.Ticks);
        }

        public static int GenerateCode(SecurityToken securityToken, string modifier = null)
        {
            if (securityToken == null)
            {
                throw new ArgumentNullException("securityToken");
            }
            ulong currentTimeStepNumber = GetCurrentTimeStepNumber();
            int result;
            using (HMACSHA1 hMACSHA = new HMACSHA1(securityToken.GetDataNoClone()))
            {
                result = ComputeTotp(hMACSHA, currentTimeStepNumber, modifier);
            }
            return result;
        }
    }

    internal sealed class SecurityToken
    {
        private readonly byte[] _data;
        public SecurityToken(byte[] data)
        {
            this._data = (byte[])data.Clone();
        }
        internal byte[] GetDataNoClone()
        {
            return this._data;
        }
    }
}

var stampCode ="123";

var code = Rfc6238AuthenticationService.GenerateCode(new SecurityToken(Encoding.Unicode.GetBytes(stampCode)));

生成时需要更换种子 stampCode。