Six years ago, I wrote a blog post titled Soatok’s Guide to Side-Channel Attacks in which I discussed the general topic of side-channels in cryptographic applications, and how to avoid them, with example code in PHP. I had called out that the algorithms discussed on the page cannot rule out compiler or runtime optimizations that undermine your security goals: You can achieve algorithmic constant-time, but any higher assurance was outside the scope of the work being done. For that reason, we’re g...