Different Hash

[arggg]

I'm a bit confused on this one. I created a DLL in 3.5 .NET and on my Vista Laptop the md5 hash is different from the md5 hash on my XP Desktop. It is the EXACT same file as I downloaded it from the same location however they both run fine just the hash is different? Can anyone explain this?

I have my update program checking files hash's against an XML file so see if new updates are available and this is causing a problem as everytime the update is run it says there are new updates because of the hash mismatch.

This is only happening to the DLL. The .exe's that were created on my Vista Laptop (Same as the .dll) have the same has on both the XP and Vista pc. I Can't explain it...

[Teme64]

Do you use similar code to calculate MD5 as below:

Dim ResultMD5() As Byte
Dim ProvMD5 As MD5
 
ProvMD5 = MD5CryptoServiceProvider.Create()
ProvMD5.Initialize()
ResultMD5 = ProvMD5.ComputeHash(BytesIn)
 

Do you convert resulting MD5 to a 32-character long string? If you do, do you have leading zeros, so that the string is 32-character long?
One other thing could be "off by one error". I used following (simplified) code to calculate MD5:

BufSize = CInt(StreamIn.Length)
ReDim MemBuf(BufSize - 1)
StreamIn.Read(MemBuf, 0, BufSize)
' Calculate MD5

and in the verification code I had

BufSize = CInt(StreamIn.Length)
ReDim MemBuf(BufSize)
StreamIn.Read(MemBuf, 0, BufSize)
' Calculate MD5

so I allocated 1-byte larger buffer which caused MD5 to differ.

Does your code produce correct MD5-values on the same OS, like in XP?

Basically, there shouldn't be any difference between XP and Vista that causes different MD5 values.

[arggg]

I'm using C# MD5CryptoServices

[arggg]

Here is my code

        /*
         * MD5 Hash
         */
        public static string GetMD5Hash(string pathName)
        {
            string strResult = "";
            string strHashData = "";
 
            byte[] arrbytHashValue;
            System.IO.FileStream oFileStream = null;
 
            System.Security.Cryptography.MD5CryptoServiceProvider oMD5Hasher =
                       new System.Security.Cryptography.MD5CryptoServiceProvider();
 
            try
            {
                oFileStream = GetFileStream(pathName);
                arrbytHashValue = oMD5Hasher.ComputeHash(oFileStream);
                oFileStream.Close();
 
                strHashData = System.BitConverter.ToString(arrbytHashValue);
                strHashData = strHashData.Replace("-", "");
                strResult = strHashData;
            }
            catch (System.Exception ex)
            {
                /*System.Windows.Forms.MessageBox.Show(ex.Message, "Error!",
                           System.Windows.Forms.MessageBoxButtons.OK,
                           System.Windows.Forms.MessageBoxIcon.Error,
                           System.Windows.Forms.MessageBoxDefaultButton.Button1);*/
                return "0";
            }
 
            return (strResult);
        }
 

the md5 for my .dll file differs on xp and vista however the 2 .exe's do not differ.

EDIT: i dont know why provider is split into provi der but it is together in my code.

[arggg]

It doesnt seem to be an issue with the code that gets the MD5 as I have another md5 program which runs as a shell on both my xp and vista machines and they both display different hashes for the same file which is the dll as well.

Here is the code for PB_Sock.dll

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Windows.Forms;
 
 
namespace PB_Sock
{
    public class AuthSock
    {
        [DllImport("user32.dll", EntryPoint="MessageBox")]
        public static extern int ShowMessage(int hWnd, string text, string caption, uint type);
 
        string loginUrl = "http://website.com/update.php?action=auth&login={0}&password={1}";
 
        public bool getAuthenticated(String user, String pass)
        {
            // *** Establish the request
 
            String loginUrlSend = String.Format(loginUrl, user, pass);
            HttpWebRequest Http =(HttpWebRequest) WebRequest.Create(loginUrlSend);
 
            // *** Set properties
            Http.Timeout = 7000;    // 7 secs
            Http.UserAgent = "PATc v" + 
                Assembly.GetExecutingAssembly().GetName().Version.ToString() + " Client";
 
            // *** Retrieve request info headers
            try
            {
                HttpWebResponse WebResponse = (HttpWebResponse)Http.GetResponse();
                Encoding enc = Encoding.GetEncoding(1252);  // Windows default Code Page
 
                StreamReader ResponseStream = new StreamReader(WebResponse.GetResponseStream(), enc);
 
                string Html = ResponseStream.ReadToEnd();
                string status = WebResponse.StatusCode.ToString();
 
                WebResponse.Close();
                ResponseStream.Close();
                if (status.Contains("OK") == true)
                {
                    if (Html.CompareTo("OK") == 0)
                    {
                        return true;
                    }
                    else
                    {
                        return false;
                    }
                }
                else
                {
                    return false;
                }
            }
            catch
            {
                MessageBox.Show("Could not establish a connection with the authentication server.",
                    "Authentication Error",MessageBoxButtons.OK,MessageBoxIcon.Error);
                    return false;
            }
        }
    }
}
 

[arggg]

Any ideas on what is going on?