Flex 4.0 HMAC.hash二进制数据

Question

I have the following PHP code, which I need to get working in Flex 4.0:

$mac = base64_encode(hash_hmac('sha256', $message, $secret, true));

If the last element is a true the hash_hmac is outputted as raw binary data, if it is false outputs lowercase hexits.

I have the following code written in Flex:

encryptedString = HMAC.hash(tempString,message,algorithm); 

However, it outputs it as lowercase hexit. I can not find out how to convert the Flex output to binary data to match the PHP.

Does anyone know?