Merge "Simplify passwordToHistoryHash()"

        try {

            MessageDigest sha256 = MessageDigest.getInstance("SHA-256");

            sha256.update(hashFactor);

            byte[] saltedPassword = Arrays.copyOf(passwordToHash, passwordToHash.length

                    + salt.length);

            System.arraycopy(salt, 0, saltedPassword, passwordToHash.length, salt.length);

            sha256.update(saltedPassword);

            Arrays.fill(saltedPassword, (byte) 0);

            sha256.update(passwordToHash);

            sha256.update(salt);

            return new String(HexEncoding.encode(sha256.digest()));

        } catch (NoSuchAlgorithmException e) {

            throw new AssertionError("Missing digest algorithm: ", e);