//需要using
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.VisualBasic;
using Microsoft.VisualBasic.CompilerServices;
using System.Security.Cryptography;
using System.IO;
using System.Data;
using System.Security;
using System.Diagnostics;
using System.Collections;

 private static TripleDESCryptoServiceProvider TDES=new TripleDESCryptoServiceProvider();

        private static SHA256Managed sha256=new SHA256Managed();

private static string Decode(byte[] p0, byte[] p1)
        {
            ICryptoTransform transform = null;
            string str;
          
                byte[] buffer = Convert.FromBase64String(Encoding.UTF8.GetString(p0));
                using (MemoryStream stream = new MemoryStream(buffer))
                {
                    byte[] buffer2 = new byte[buffer.Length + 1];
                    transform = TDES.CreateDecryptor(p1, ConvertToByteArray(p1, TDES.IV.Length));
                    using (CryptoStream stream2 = new CryptoStream(stream, transform, CryptoStreamMode.Read))
                    {
                        stream2.Read(buffer2, 0, buffer2.Length);
                    }
                    str = Encoding.UTF8.GetString(buffer2).Replace("\0", "");
                }
         
            return str;
        }

               private static byte[] ConvertToByteArray(byte[] p0)
        {
            //int length = 111;
            int length = TDES.Key.Length;
            if (p0.Length == length)
            {
                return p0;
            }
            byte[] destinationArray = new byte[(length - 1) + 1];
            Array.Copy(sha256.ComputeHash(p0), destinationArray, (int)(length - 1));
            return destinationArray;
        }

        private static byte[] ConvertToByteArray(byte[] p0, int p1)
        {
            byte[] destinationArray = new byte[(p1 - 1) + 1];
            Array.Copy(sha256.ComputeHash(Encoding.UTF8.GetBytes(Encoding.UTF8.GetString(p0))), destinationArray, (int)(p1 - 1));
            return destinationArray;
        }

//解密调用
Decode(Encoding.UTF8.GetBytes("字符串"), ConvertToByteArray(Encoding.UTF8.GetBytes("test")))

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