How to use hash sha256 in zoho creator?

How to use hash sha256 in zoho creator?

Hello everyone, 
I need to ask you about hash function in zoho creator. 
Because I want to import some data from another website, and in that website, it need to has their signature in SHA256. 
In PHP, its very easy, you just use the HMAC function:

"string hash_hmac ( string $algo , string $data , string $key [, bool $raw_output = false ] )"

But its so hard in zoho. Its cost me 1 month to find solution for this.

If there is no way to has string by SHA256 in zoho creator, could anyone please give me the website could has with the Rest API that I could call that website in zoho? 
Thank you.