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 string, but when I try to hash the sha256 hash with ripemd160 I get a hash which is incorrect.

According to online hash calculators, the SHA256 value of the string 'test'(all lowercase) is:

9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08

And the RIPEMD160 value of the string 'test' is:

5e52fee47e6b070565f74372468cdc699de89107

The value from hashing the resulting sha256 hash with ripemd160 according to online calcs is:

4efc1c36d3349189fb3486d2914f56e05d3e66f8

And the one my app gives me is:

cebaa98c19807134434d107b0d3e5692a516ea66

which is obviously wrong.

Here is my code:

public static String toRIPEMD160(String in)
{
    byte[] addr = in.getBytes();
    byte[] out = new byte[20];
    RIPEMD160Digest digest = new RIPEMD160Digest();
    byte[] sha256 = sha256(addr);
    digest.update(sha256,0,sha256.length);
    digest.doFinal(out,0);
    return getHexString(out);
}

public static byte[] sha256(byte[] data)
{
    byte[] sha256 = new byte[32];
    try
    {
        sha256 = MessageDigest.getInstance("SHA-256").digest(data);
    }
    catch(NoSuchAlgorithmException e)
    {}

    return sha256;
}

For the ripemd160 algorithm, you need bouncycastle and java.security.MessageDigest for sha256.

Answer 1

Your "online calculator" result is the result of hashing the bytes of the string "test" with SHA-256, converting the result of that hash to a hex string, then taking the bytes corresponding to the ASCII characters of that hex string and hashing those a second time. This is very different from your Java code, which passes the bytes that come out of the first hash directly to the second one, without printing them as hex and turning those characters back into bytes in between. The single byte with value 254 (decimal) becomes "fe" in hex, which becomes the two-byte sequence [0x66, 0x65] when converted back to bytes.