Combination in lis_result_sourcedid in Quiz submission

[sivashankary]

I wanted to confirm that what details combine to create lis_result_sourcedid?

According to my findings if we have 

"lis_result_sourcedid":"AAAAA-BBBBB-CCCCCC-DDDDDD-XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" which is formed by 
tool_id : AAAAA
custom_canvas_course_id : BBBBB
custom_canvas_assignment_id : CCCCCC
custom_canvas_user_id : DDDDDD
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

What is this XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX? How does canvas calculate it?

Can someone please confirm my findings and fill me in with the missing piece?
Thanks

[ColinMurtaugh]

I'd look here in the Canvas source code: https://github.com/instructure/canvas-lms/blob/9a9fdf3a6594c6c9a083c80554e2f048ad5376d4/app/models/l...

It looks to me like that last component is the "pre-determined shared secret that the tool signs requests with". 

However, I would be very careful about making any assumptions about that value that are not documented in the API docs. 

--Colin