4 ms·

Some feedback: * don't use md5 as a security feature! I suggest to replace the use of md5sum with sha256sum (not even sha1sum is really safe anymore). The only

by pflanze 13y ago

Some feedback: * don't use md5 as a security feature! I suggest to replace the use of md5sum with sha256sum (not even sha1sum is really safe anymore). The only use of seeing md5 in security contexts is to indicate that the person recommending its use doesn't understand security, which may admittedly be a worthwhile feature in itself. Perhaps you're really saying "this is one of the weak links in our security chain, the source code we're getting here might be hijacked or have huge security holes, and I haven't checked the sources, so it doesn't matter much anyway whether you're using the same sources as me anyway"? Then perhaps point this out, like using sha256sum and at the same time mention "(although I haven't verified the source code against security issues or backdoor (yet?))". * I'm not a cryptologist, but regarding "the security of encryption depends upon how random the pseudo-random number generation on your system.." I think that's the wrong use of the term "pseudo-random number", as /dev/random really is about randomness, not pseudo-random numbers at all. /dev/urandom does stretch the collected entropy using pseudo-random number generation, but I think even the phrase "how random the pseudo-random generation" is mathematical nonsense, as it's not random at all, just random-looking when not knowing the generator inputs. Perhaps say "The security of encryption depends upon the randomness of the random source used on your system"? (* I think the NSA is able to track you anyway, regardless of whether you're using your own server on the same IP or not. Thus the suggestion "make you more vulnerable to traffic analysis" will probably only hold for companies trying to track you.)

motters 13y ago
Good points. Thanks. I used md5sum mainly because it was given on the original sites from which software was downloaded, but if sha256sum is more unique then I'll use that instead. Although there are some systems where I'm familiar with the code - such as Bitmessage - in most cases I havn't personally checked the code myself. Ideally Freedombone would be a pure blend (I think that's also the aim of FreedomBox), but for now it does involve downloading some non-packaged systems.
- pflanze 13y ago
  > more unique That makes it sound like you're thinking that the chances for a conflict (same hash value) depend just on the size of the hash value. But it's worse than that, thanks to algorithmic insights, inputs that produce the same hash value can be found more cheaply than just by chance. Also, they can be found so cheaply that it's computationally trivial to do even for an individual [1]. Thus anyone who can change what data you receive, can trivially also make it hash to the same MD5. (I haven't checked whether publicly available software exists to generate conflicting files that are also, for example, valid gzip files, but I surely expect that an entity like the NSA (and perhaps blackhats, too) can create such software on their own.) [1] "produce a collision for two inputs with specified prefixes within hours, using off-the-shelf computing hardware": https://en.wikipedia.org/wiki/Md5#Security https://en.wikipedia.org/wiki/Md5#Security Yes, there are many sites that still tell users to check MD5 hashes. I think it's evident that those are totally worthless for some years now. Worse, it may be giving some people a false sense of security. OTOH those places might give those who do know a hint that perhaps the authors or distributors don't know about security. (Sorry for the harsh words...)
  - motters 13y ago
    Thanks for the information about this. I didn't know that md5 was quite that easy to fool. The hashes have been duly changed to using sha256sum. I'll file bug reports for any md5 hashes that I see in future.
- dredmorbius 13y ago
  I used md5sum mainly because it was given on the original sites from which software was downloaded That is indeed a limitation. I'd suggest you explain what md5sum is, how to use it, and what its limitations are -- specifically that collisions are now trivial to instrument. Developers / vendors still relying on md5sum really should be named and shamed these days.

by pflanze 13y ago

motters 13y ago

Good points. Thanks. I used md5sum mainly because it was given on the original sites from which software was downloaded, but if sha256sum is more unique then I'll use that instead. Although there are some systems where I'm familiar with the code - such as Bitmessage - in most cases I havn't personally checked the code myself. Ideally Freedombone would be a pure blend (I think that's also the aim of FreedomBox), but for now it does involve downloading some non-packaged systems.

pflanze 13y ago
> more unique That makes it sound like you're thinking that the chances for a conflict (same hash value) depend just on the size of the hash value. But it's worse than that, thanks to algorithmic insights, inputs that produce the same hash value can be found more cheaply than just by chance. Also, they can be found so cheaply that it's computationally trivial to do even for an individual [1]. Thus anyone who can change what data you receive, can trivially also make it hash to the same MD5. (I haven't checked whether publicly available software exists to generate conflicting files that are also, for example, valid gzip files, but I surely expect that an entity like the NSA (and perhaps blackhats, too) can create such software on their own.) [1] "produce a collision for two inputs with specified prefixes within hours, using off-the-shelf computing hardware": https://en.wikipedia.org/wiki/Md5#Security https://en.wikipedia.org/wiki/Md5#Security Yes, there are many sites that still tell users to check MD5 hashes. I think it's evident that those are totally worthless for some years now. Worse, it may be giving some people a false sense of security. OTOH those places might give those who do know a hint that perhaps the authors or distributors don't know about security. (Sorry for the harsh words...)
- motters 13y ago
  Thanks for the information about this. I didn't know that md5 was quite that easy to fool. The hashes have been duly changed to using sha256sum. I'll file bug reports for any md5 hashes that I see in future.
dredmorbius 13y ago
I used md5sum mainly because it was given on the original sites from which software was downloaded That is indeed a limitation. I'd suggest you explain what md5sum is, how to use it, and what its limitations are -- specifically that collisions are now trivial to instrument. Developers / vendors still relying on md5sum really should be named and shamed these days.