> (Admittedly, candidates are likely to have memorized the algorithm for reversing a binary tree since that is such a common interview question)

Exactly my point. Testing for "how to implement a known algorithm" is much the same as recalling facts about TLS. You're testing recall only.

You're testing recall only when asking about TLS. You may be testing recall for "how to implement a known algorithm", but there's still plenty of room for testing actual problem solving too.

If you are the interviewer, even if you are asking a standard "how to invert a binary tree" type algorithm question, you hold the cards to keep pushing the bounds for problem solving by extending the question.

Well if you're willing to push boundries, you can certainly do the same with TLS. Ask why the TLS spec does X instead of Y, for various subtle design decisions. This is probably actually much easier to do than with a binary tree, as TLS is a lot more complex and a lot more subtle. It would certainly be an appropriate line of questioning if you were hiring a crypto engineer, not sure it would be relavent to a security engineer or software engineer.