# Building a Createandassociate message in Postman -- need header help

**URL:** <https://devforum.zoom.us/t/building-a-createandassociate-message-in-postman-need-header-help/142308>\
**Category:** Meetings\
**Created:** [March 5, 2026, 2:10pm UTC](https://devforum.zoom.us/t/building-a-createandassociate-message-in-postman-need-header-help/142308 "2026-03-05T14:10:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![KenBanks](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/kenbanks/32/57828_2.png) [@KenBanks](https://devforum.zoom.us/u/KenBanks)\
**Post date:** [March 5, 2026, 2:10pm UTC](https://devforum.zoom.us/t/building-a-createandassociate-message-in-postman-need-header-help/142308/1 "2026-03-05T14:10:14Z")

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### I am trying to build a post message using the Zoom LTI Pro API in Postman. Specifically a createAndAssociate post message. I found the article on how to do this in the Zoom support.

I understand all the elements of the body, which is the request schema well enough that I believe I have this part correct.

Where I need some help is the request header section. There is step #3, which is creating the signature; the query parameters are fairly straightforward. The part that I am failing is how do I complete step #3 and step#4:

1. The signature is calculated by passing the base string and secret to the HMAC-SHA1 hashing algorithm. The calculated signature is then converted to aencodeBase64URLSafeString.

2. Pass the value obtained from step 3 in the X-Lti-Signatureheade

Any help or a sample that includes that part of the process would be very much appreciated.