4 ms·
>There's like an obvious lesson here about PGP and the MDC, right? Not sure that all the readers will already know about our constant quibbling about the secur
by upofadown 3y ago
>There's like an obvious lesson here about PGP and the MDC, right?
Not sure that all the readers will already know about our constant quibbling about the security of the MDC. I have in the past suggested that the fact that the MDC has remained unbroken for 20+ years is evidence that it is secure.
Interestingly enough, I have recently stumbled across a paper[1] that shows that preventing an attacker from computing the hash is important for insuring the security of hash than encrypt schemes like the MDC. OpenPGP does that by preseeding the hash with a random, encrypted value.
So does that mean that the MDC is secure? Unfortunately, when you come up with a set of requirements for security, you have to use your knowledge of existing attacks. You don't get to know about about future attacks. So the fact that a particular construct has never been broken over a long time is in a sense the only objective evidence available.
[1] https://cseweb.ucsd.edu/~mihir/papers/enc-red.pdf https://cseweb.ucsd.edu/~mihir/papers/enc-red.pdf
- tptacek 3y agoThe MDC thing has nothing to do with you. It's a perennial complaint among cryptographers about how PGP's design has escaped modernity. It's weird that you think HN is somehow the center of that phenomenon.
- upofadown 3y agoThen what does the MDC thing have to do with any of this?
- tptacek 3y agoIt's an archaic premodern construction that cryptographers hate but that hasn't been demolished in a paper yet, in part because lots of people use SSH and very few people seriously use PGP. I'm confused, though: what would it have to do with you?
- upofadown 3y ago>...hasn't been demolished in a paper yet... OpenPGP gets a fair amount of academic scrutiny. What is going to change that would allow someone to find a weakness in OCFB-MDC at this late date? Also, why do you care so much that you bring it up out of nowhere in unrelated contexts?
- tptacek 3y agoNot really, no, it doesn't. I don't understand your second question.
- mbauman 3y ago> I have in the past suggested that the fact that the MDC has remained unbroken for 20+ years is evidence that it is secure. This seems like... not a great stance to take on post about a vulnerability that existed for 20+ years. I don't understand the defensiveness.