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 r

Answer 1

This is a slight variation of Andranik and Den Delimarsky answers above, but its a bit more concise and doesn't require any bitwise logic. Instead it uses the built-in String.format method to convert the bytes to two character hexadecimal strings (doesn't strip 0's). Normally I would just comment on their answers, but I don't have the reputation to do so.

public static String md5(String input) {
    try {
        MessageDigest md = MessageDigest.getInstance("MD5");

        StringBuilder hexString = new StringBuilder();
        for (byte digestByte : md.digest(input.getBytes()))
            hexString.append(String.format("%02X", digestByte));

        return hexString.toString();
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
        return null;
    }
}

If you'd like to return a lower case string instead, then just change %02X to %02x.

Edit: Using BigInteger like with wzbozon's answer, you can make the answer even more concise:

public static String md5(String input) {
    try {
        MessageDigest md = MessageDigest.getInstance("MD5");
        BigInteger md5Data = new BigInteger(1, md.digest(input.getBytes()));
        return String.Format("%032X", md5Data);
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
        return null;
    }
}