Compute signature of a http from Hoiio. This is used to authenticate the notification from Hoiio. Match this computed signature with the HTTP header "X-Hoiio-Signature".

HoiioSignature.java

public String computeHoiioSignature(byte[] payload, String accessToken) {
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    md.update(payload);
    md.update(accessToken.getBytes("UTF-8"));
    byte[] bytes = md.digest();
    String mySign = Hex.encodeHexString(bytes);
    return mySign;
}