MD5 hashing in Android

Question

I have a simple android client which needs to 'talk' to a simple C# HTTP listener. I want to provide a basic level of authentication by passing username/password in POST requests.

MD5 hashing is trivial in C# and provides enough security for my needs but I can't seem to find how to do this at the android end.

EDIT: Just to address the concerns raised about MD5 weakness - the C# server runs on the PCs of the users of my android client. In many cases, they'll be accessing the server using wi-fi on their own LANs but, at their own risk, they may choose to access it from the internet. Also the service on the server needs to use pass-through for the MD5 to a 3rd party application I have no control over.

Answer 1

Here is an implementation you can use (updated to use more up to date Java conventions - for:each loop, StringBuilder instead of StringBuffer):

public static String md5(final String s) {
    final String MD5 = "MD5";
    try {
        // Create MD5 Hash
        MessageDigest digest = java.security.MessageDigest
                .getInstance(MD5);
        digest.update(s.getBytes());
        byte messageDigest[] = digest.digest();

        // Create Hex String
        StringBuilder hexString = new StringBuilder();
        for (byte aMessageDigest : messageDigest) {
            String h = Integer.toHexString(0xFF & aMessageDigest);
            while (h.length() < 2)
                h = "0" + h;
            hexString.append(h);
        }
        return hexString.toString();

    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return "";
}

Although it is not recommended for systems that involve even the basic level of security (MD5 is considered broken and can be easily exploited), it is sometimes enough for basic tasks.