5 ms·
It's not quite that simple. When cryptographic functions are broken, practical vulnerabilities are usually years away. A reduced SHA-1 collision time is certain
by weavejester 15y ago
It's not quite that simple. When cryptographic functions are broken, practical vulnerabilities are usually years away. A reduced SHA-1 collision time is certainly a good reason to move away from SHA-1, but it doesn't mean that an attacker can compromise an existing piece of code secured by a SHA-1 hash.
In this case, it is not merely sufficient to find a collision, but to find a collision that is also a valid Git commit, implements a vulnerability, and, ideally, is not immediately obvious at first glance it is a hack (i.e. having kilobytes of garbage data in the commit diff). This is much harder than just finding a random set of bytes that just happens to match the commit SHA-1.
Now, it could be that an organisation like the NSA is sufficiently ahead of public crypto technology that it is capable of not only finding a SHA-1 collision in feasible time, but is also able to craft a malicious Git commit with an identical SHA-1 to a legitimate commit. Inserting such a commit into the Linux source in an appropriate place might result in compromised kernels appearing in commercial products.
But... I kinda doubt anyone is that far ahead, and in any case, it seems extremely risky to try to play such a high-value advantage in a public repository. If someone happens to spot your faked commit, suddenly everyone knows what you are capable of.
So whilst Git would be more secure using SHA-512 or an equivalent, it's currently very unlikely that anyone has the practical capability and will to compromise the kernel's commit log.
- andrewcooke 15y agoi am not saying git is insecure - i am saying someone needs to do exactly the analysis you are sketching. you can wave your hands and say that this is not a problem, but it's been 6 years since sha-1 was broken and that's an awfully long time. also, i find it absolutely typical of the place that HN has become that my original post asking a reasonable, informed question with reference is voted down. you're a bunch of mindless fucking morons.
- weavejester 15y agoYour comment was accurate, but somewhat combative, which may be why it was down-voted. I suspect if you had said the same thing, but had phrased it a little differently, it would have been up-voted. That said, it was not an unreasonable question to ask, and so I've up-voted you. What doesn't help is calling everyone "mindless fucking morons" after only one or two down-votes. It's not constructive, and won't get you anywhere. Also: chill. Just because one or two individuals didn't like the tone of your original comment, doesn't mean everyone on HN is out to get you. Well, at least not before you insulted them.
- pak 15y agoIt might have also been > is their any real analysis driving some of the downvotes (I did not vote myself).
- monochromatic 15y agoI find it absolutely typical of the place that HN has become that people give a shit about karma.
- Symmetry 15y agoBetween the spelling mistake, lack of capitalization, and tone I certainly would have voted it down if it hadn't been the only post in this thread bringing up an important point. As it was I felt I had to vote up.