S/MIME didn’t have one less footgun: it had roughly the same footgun. The fact that GPG prints a warning isn’t the footgun, the footgun is the fact that decrypt

S/MIME didn’t have one less footgun: it had roughly the same footgun. The fact that GPG prints a warning isn’t the footgun, the footgun is the fact that decrypted plaintext was returned even if the MDC check failed. The point of considering each thing that could have prevented an attack is clear, and is a central part of threat modeling and defense in depth. Those concepts aren’t really controversial. Thinking critically about the parts of a system that can contribute to adverse results, and then applying mitigations and avoiding pitfalls, is a pretty core part of basically all engineering (software and otherwise). The bus analogy (if I hadn’t left the house on the day I got hit by a bus, I’d not have gotten hit) would, in a threat modeling context, be accurately identified as both ‘definitely true’ and ‘low probability’. Yes, leaving your house is dangerous, for a variety of reasons. But the relative danger of leaving your house vs not leaving your house is more questionable (staying inside the house is likewise dangerous), and the probability of leaving-the-house causing hit-by-bus is low. But a security tool returning plaintext despite a MAC fail isn’t like leaving your house, it’s like looking both ways once you’re already crossing the street. GPG warns you there’s a car coming, but you’re already standing in front of the car. A dexterous human could potentially dive out of the way, as an end-use implementation could discard the decrypted plaintext when it sees the MDC warning, but a root-cause-analysis would still rightly suggest that you should be looking both ways before crossing, rather than during. Taking this thread in aggregate, it’s interesting to me how the goalposts keep shifting. The original thrust was “There were no real weaknesses in the OpenPGP standard or the GnuPG implementation of that standard”. When pressed, your position shifted to include “Even if the GPG implementation and/or OpenPGP standard had of been entirely broken, this is still mostly the email clients fault.” You’ve now further shifted to questioning why we should even worry about whether GPG could be better (“What point is there in considering each and every thing that could of been different that would of prevented the attack?”). I don’t understand the rigidity with which you refuse to consider the possibility that GPG could have better handled this kind of threat.