SecretKeySpec signingKey = new SecretKeySpec(sha256Bytes(privateKey), "SHA-256");
Mac mac = Mac.getInstance("HmacSHA256");
mac.init(signingKey);
byte[] rawMac = mac.doFinal(content.getBytes("UTF-8"));
byte[] hexBytes = new Hex().encode(rawMac);
hash = new String(hexBytes, "ISO-8859-1");
} catch (Exception e) {
throw new RuntimeException(e);
}
return hash;