How can you generate the same MD5 Hashcode in C# and Java?

Question

I have a function that generates a MD5 hash in C# like this:

MD5 md5 = new MD5CryptoServiceProvider();
byte[] result = md5.ComputeHash(data);
StringBuilder s         


        

Answer 1

I know this topic is old but I ran into the same issue just now and couldn't find an answer that worked for me. I was writing a patcher for a game and needed the md5 hashcode of files as a way to ensure that the files are up to date, but C# and Java gave me different strings although the files were identical.

Here's how I solved it:

C# Code:

public static string getMD5(string fullPath)
{
    MD5 md5 = MD5.Create();
    using (FileStream stream = new FileStream(fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    {
        byte[] hash = md5.ComputeHash(stream);
        StringBuilder sb = new StringBuilder();
        for (int j = 0; j < hash.Length; j++)
        {
            sb.Append(hash[j].ToString("X2"));
        }
        return sb.ToString();
    }
}

This creates a 32 character hex string. Apache Commons DigestUtils.md5Hex(InputStream) does the same, now the only different is that the C# example returns an uppercase string, so the solution is simply to convert the hash from the Java program to an uppercase string.

Java code:

public static String checkSumApacheCommons(String filePath)
{
    String checksum = null;
    try 
    {  
         checksum = DigestUtils.md5Hex(new FileInputStream(filePath));
    }
    catch (IOException ex) 
    {
        ex.printStackTrace(System.out);
    }
    return checksum.toUpperCase();
}

The produced hashes look like F674865D8A44695A2443017CFA2B0C67.

Hope this helps someone.