Cannot output correct hash in Java. What is wrong?

Question

In my Android app I have a SHA256 hash which I must further hash with the RIPEMD160 message digest algorithm.

I can output the correct sha256 and ripemd160 hash of any s

Answer 1

Your hash is working fine. The problem is that the online calculators that you're using are treating your input:

9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08

as a string instead of an array of bytes. In other words, it's treating each character as a byte instead of parsing character pairs as bytes in hexadecimal. If I give this as a string to online calculators, I indeed get exactly what you got:

4efc1c36d3349189fb3486d2914f56e05d3e66f8

However, you're treating the output as an array of bytes instead of a String and that's giving you different results. You should encode your raw SHA256 hash as a string, then pass the encoded string to the hash function. I see you have a getHexString method, so we'll just use that.

public static String toRIPEMD160(String in) {
    try {
        byte[] addr = in.getBytes();
        byte[] out = new byte[20];
        RIPEMD160Digest digest = new RIPEMD160Digest();

        // These are the lines that changed
        byte[] rawSha256 = sha256(addr);
        String encodedSha256 = getHexString(rawSha256);
        byte[] strBytes = encodedSha256.getBytes("UTF-8");
        digest.update(strBytes, 0, strBytes.length);

        digest.doFinal(out, 0);
        return getHexString(out);
    } catch (UnsupportedEncodingException ex) {
        // Never happens, everything supports UTF-8
        return null;
    }
}

If you want to know it's working, take the value of encodedSha256 and put that into an online hash calculator. As long as the calculator uses UTF-8 encoding to turn the string into a byte array, it will match your output.