[ircmaxell]

The far better approach is to just make the operations not depend on the secret.

You only really need to worry about timing attacks for values that the attacker doesn't know, and you don't want them to know.

So it's only things like encryption keys, passwords, session identifiers, reset tokens, etc that you need to worry about.

> And programmers who touch sensitive code can easily forget the requirement for constant-time behaviour.

And that's why I support the discussion we were having on PHP's internals list where we talked about making functions which are commonly used with secrets timing safe by default. As long as there isn't a non-trivial performance penalty to it at least.

As far as worrying about it, I'd rather people understand SQLi and XSS better. They are both FAR bigger surface areas than a timing attack ever will be. And likely going to be the bigger threat to 99.99% of applications.