Concise Hawk Doc

[Jonathan Rudenberg]

I've put together a concise description[1] of the Hawk algorithms (as I understand them). This is not intended to replace the Hawk README, but tries to lay Hawk out in format that allows easy understanding of implementation details for client developers. It is focused on Hawk's usage in Tent, but should be useful generally as well.

Feel free to take a look, and let me know if anything is unclear or incorrect.

Jonathan

[1] https://tent.io/docs/authentication