Onbo generates an HMAC for every webhook message sent to your platform. The HMAC generation algorithm is the same as the one used for API Authentication.

HMAC Generation

The HMAC algorithm requires three components:

url uri The full url of the request, for example

md5 string The request's body after removing white-spaces and line-breaks (according to regex

/(\r\n|\n|\r|\s+)/gm), which will then be hashed with the MD5 algorithm.

epoch int Number representation of Unix Epoch time

Supply these three components to the HMAC-SHA256 algorithm to create an HMAC value:

body =request.body.toString().replace(/(\r\n|\n|\r|\s+)/gm, '');
md5 = "";
if (body != ""){
    md5 = CryptoJS.MD5(body).toString()

hmac = CryptoJS.HmacSHA256(url + content-md5 + epoch, key).toString();

A more verbose example of the HMAC creation can be seen on Postman's Collection Pre-Request Script, where you can see the HMAC is automatically calculated in runtime before every request. For security purposes, the HMAC hash will only be valid for 60 seconds. Attempting to use an expired HMAC will result in HTTP Status 403: Forbidden.

Authentication Header

Using the HMAC method described above, Onbo calculates and sends X_STILT_HMAC and EPOCH as a part of the webhook request.


The HMAC (as generated above)


Number representation of Unix Epoch time

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