> confidence and toolkit to write my own cryptographic protocols
One of the first things I ever learned in Dan Boneh's Crypto MOOC is to not write your own crypto protocols for your product.
Because old solutions exist for a long time, and have been open for a long time, experts and scholars have had much more time to find faults in them. They are also tested in the industry.
No matter how smart you are, you shouldn’t use your own cryptographic solution.
Use open, long-existed, tried and true solutions.