Last year, almost exactly to the day, I declared HPKP effectively dead. I believed then—and I still do—that HPKP is too complex and too dangerous to be worth the effort. The biggest problem lies in the fact that there is no sufficient margin of safety; pinning failures are always catastrophic. That’s always bothered me and I wondered if it was possible to somehow fix HPKP without starting from scratch. That’s what this blog post is about.