I have no idea what I am doing...

import org.bouncycastle.crypto.generators.PKCS5S2ParametersGenerator;
import org.bouncycastle.crypto.params.KeyParameter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;

public class Authentication {

    private static Logger LOGGER = LoggerFactory.getLogger(Authentication.class.getCanonicalName());

    // Are these sizes arbitrary ?
    private static final int SEED_BYTES = 20;
    private static final int HASH_BYTES = 20;

    // increase iterations as high as your performance can tolerate
    // since this increases computational cost of password guessing
    // which should help security
    private static final int ITERATIONS = 1000;
    //Encoding
    public static final String ENCODING = "UTF-8";

    public String generateSalt() {
        return new String(new SecureRandom().generateSeed(SEED_BYTES));
    }

    public String hashToken(String password, String salt) {
        try {
            PKCS5S2ParametersGenerator kdf = new PKCS5S2ParametersGenerator();
            kdf.init(password.getBytes(ENCODING), salt.getBytes(ENCODING), ITERATIONS);
            return new String(((KeyParameter) kdf.generateDerivedMacParameters(8 * HASH_BYTES)).getKey());
        } catch (UnsupportedEncodingException exception) {
            LOGGER.info("Error when hashing password : {}", exception.getMessage());
        }
        return null;
    }

    public boolean isPasswordValid(String givenPassword, String salt, String storedHash) {
        return this.hashToken(givenPassword, salt).equals(storedHash);
    }

}