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Yahoo discloses hack of 1B accounts

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Re: Yahoo discloses hack of 1B accounts

#241

Post by rev_bird »

duskwuff wrote: post #162
funnyfacts365 wrote: post #143

Earlier quoted context omitted.

Care to explain? The hashes are what is compared so it seems it's important.

The existence of crafted collisions -- being able to create a pair of M1 and M2 such that MD5(M1) = MD5(M2) -- is primarily relevant to situations where MD5 is being used as a signature algorithm, such as in certificate issuance. In these applications, being able to generate a pair of documents with the same hash is catastrophic. Being able to generate a pair of passwords that are treated as equal, on the other hand,…

I'm a total greenhorn when it comes to cryptography, but the difference between these two situations was totally lost on me until I read this comment. When I see, "It's easy to create MD5 collisions," my first thought is, "If you give me a hash, it's easy to find a string that results in an identical hash." If I'm understanding this right, that would be a "preimage attack," and would be bad for all the reasons being discussed in this thread.

However, it seems like "It's easy to create MD5 collisions," at least as it is true today, actually means something different: That, given a string, it's easy to find a second string that shares the same hash. If that's the case, I have two questions:

* I am totally lost as to how these are different scenarios. There's no difference I can see between "Here's string A" and "here's the hash of string A," if the goal is to find a "string B" that shares the hash. Are these "crafted collisions" generated by modifying string A and string B, until a collision pops out?

* If that's the case... what's everyone freaking out about? Why were people saying MD5 is unsafe 20 years ago, if even now, we can't achieve a preimage attack that can get you into an account based on the valid password's hash? Yahoo could have printed these hashes out and hung them up on posters in the mall and no one would have been able to get into accounts from it. There are dozens of comments lamenting how stupid this was, but... it seems like there's no actual problem?

Re: Yahoo discloses hack of 1B accounts

#242

Post by geofft »

JonDav wrote: post #136
metafunctor wrote: post #94

Earlier quoted context omitted.

A preimage attack for MD5 has complexity of about 2^123. So, even if you get the MD5 hash for a password, it will be exceedingly hard to find a password that has the same hash (assuming the original password is long and random).

I thought the whole point of the MD5 vulnerability was that the limit was 2^128 and as such there are more inputs that possible output hashes, meaning more possible input collisions.

Every hash has a finite output length, and therefore a finite number of possible outputs. 2^128 is a very large finite number. It's not that large in the grand scheme of things (there are over 2^260 or so atoms in the universe), and it's definitely better to use a hash with 2^256 outputs now that there exist good 256-bit hashes that are faster than MD5, but 2^128 is still quite a large number. The internets are quoting me about 10 billion hashes per second on a good GPU from a few years ago, which comes out to about one sextillion years to find an input for every possible output. (It divides linearly if you have more GPUs, but that clearly won't help very much.)

What's broken about MD5 is that, due to an algorithmic flaw, it's very easy to generate two inputs of your choice that have a matching output. That's great if you want to do things like spoof an SSL certificate (you generate two certificate signing requests, get one of them signed, apply the signature to the other), but not directly helpful for attacking a password hash where someone else chose the password.

What is conceptually broken is that such an algorithmic flaw exists, and also due to algorithmic flaws it takes a bit under 2^128 tries to find an input for a specific possible output. That worries mathematicians, because it's a sign the hash isn't behaving as randomly (speaking informally) as one would hope, and that people are starting to understand its structure. If that understanding continues, it might be broken more in the future, so you absolutely shouldn't build new systems on MD5 because we expect the research to happen at some point.

But, at least today, it's still true that you can have a password that can't be brute-forced despite the use of MD5. Maybe someone will present a paper tomorrow that disproves that.

Re: Yahoo discloses hack of 1B accounts

#243

Post by djsumdog »

kej wrote: post #218
Endy wrote: post #153

Earlier quoted context omitted.

If Yahoo goes down, I won't have email; or at best I'll maybe keep a Zoho. I hate Google's mail interface, I hate the way they make 'conversations' out of discrete emails, and I especially hate their lack of folders. I use GMail begrudgingly at work, and only when necessary, and every time, I look at it and go, "what dipshit ever thought this was a functional way to deal with email?" As a dedicated Windows user, I'm…

> I especially hate their lack of folders GMail supports labels as folders. When you create a new label it will ask you if you want to nest the label under another label and you can do this repeatedly to make a nested folder structure. Crucially, this will show up as nested folders via IMAP.

They should use IMAP labels. Their IMAP implementation has always been terrible and broken. Anything you label gets put into an IMAP folder and therefore you download it multiple times per label.

I agree; fuck everything about gmail usability. It was a cool trick when it came out. Now it's just overly bloated AJAX, non-standards compliant garbage.

Re: Yahoo discloses hack of 1B accounts

#244

Post by Endy »

eric_h wrote: post #195
Endy wrote: post #153

Earlier quoted context omitted.

If Yahoo goes down, I won't have email; or at best I'll maybe keep a Zoho. I hate Google's mail interface, I hate the way they make 'conversations' out of discrete emails, and I especially hate their lack of folders. I use GMail begrudgingly at work, and only when necessary, and every time, I look at it and go, "what dipshit ever thought this was a functional way to deal with email?" As a dedicated Windows user, I'm…

> I hate Google's mail interface Their IMAP interface is both standards compliant and fully functional. I'm not terribly fond of the Gmail web/native apps either, so I just don't use them (though I do occasionally hop on the web app when my client isn't searching the email as effectively as google does). With 2FA it can be a bit more work adding devices, but it's not a deal breaker for me.

I don't download my email. I have a webmail for a reason - I don't want a mail client with all its attendant files gumming up my PC. I moved off Netscape Communicator to webmail because it took up over 40% of my drive, and I've never regretted the decision.

And I don't like 2FA either. It's a hassle and never, ever, worth my time or energy. There was one gaming service (I think it was an MMO) that demanded 2FA or bust. I don't use that service and never will.

Re: Yahoo discloses hack of 1B accounts

#245

Post by djsumdog »

eric_h wrote: post #195
Endy wrote: post #153

Earlier quoted context omitted.

If Yahoo goes down, I won't have email; or at best I'll maybe keep a Zoho. I hate Google's mail interface, I hate the way they make 'conversations' out of discrete emails, and I especially hate their lack of folders. I use GMail begrudgingly at work, and only when necessary, and every time, I look at it and go, "what dipshit ever thought this was a functional way to deal with email?" As a dedicated Windows user, I'm…

> I hate Google's mail interface Their IMAP interface is both standards compliant and fully functional. I'm not terribly fond of the Gmail web/native apps either, so I just don't use them (though I do occasionally hop on the web app when my client isn't searching the email as effectively as google does). With 2FA it can be a bit more work adding devices, but it's not a deal breaker for me.

Their IMAP implementation is anything but compliant or functional. They implement labels as folders. Every time you use a label, it downloads that message multiple times and puts it into folders.

Also when you try to write drafts in Thunderbird for Gmail, it stores them in such a way as each saved draft turns into part of the conversation (WTF?!) It makes conversations totally unreadable.

I quite gmail years ago and do not miss their broken IMAP implementation.

Re: Yahoo discloses hack of 1B accounts

#246

Post by username223 »

phantom_oracle wrote: post #89

there's a couple of things that these major providers getting pwned teaches you: 1) their security isn't good just because of their scale/size (that begins to seem more and more like a false-assumption nowadays) 2) migrating your email to a new provider is quite difficult (consider that the average person will have just 1 - or 2 - email accounts and they link EVERYTHING to it) 3) the price of ads/convenience is no lo…

> Lastly (and I really hope this happens), Yahoo implodes/collapses (cause the average Joe won't migrate willingly) and leaves a vacuum for their 500+ million email users.

You do realize this makes you sound both terrible and ignorant, right? I happen to have a Yahoo account, which I registered way back when the options were that, Hotmail, and maybe AOL. I have self-hosted mail now, and a redirectable primary address, but that Yahoo address lives on in various address books.

If you want to realize your email dream, you should try to turn the Yahoo addresses into an eternal forwarding service for current accounts. Maybe you could sell space on the signup page to smaller providers.

Re: Yahoo discloses hack of 1B accounts

#247

Post by mturmon »

jsjohnst wrote: post #231
dsl wrote: post #208

Earlier quoted context omitted.

On a number of engagements I've come across password databases that have been migrated to bcrypt. In one case I checked CVS to see who made the code change, and found the MD5 passwords on his dev box. In another I tracked down a MySQL slave that had broken replication for over a year. In both cases I tried to track down backups, but discovered neither company was keeping them. That is another possible vector.

1) I'd be flabbergasted beyond belief if there was ever a Yahoo! engineer who had user passwords on their laptop / Dev box. The technical hurdle for that would be a stretch, let alone the fact of the other ramifications of doing this. 2) there's no SQL database involved with Yahoo!'s storage of passwords. It's a custom built db system with proprietary access and replication protocols.

Yet, somehow they did get out.

Re: Yahoo discloses hack of 1B accounts

#248

Post by Endy »

rbcgerard wrote: post #96
anton_tarasenko wrote: post #10

Yahoo's press release with details: http://www.businesswire.com/news/home/20161214006239/en/Impo...

LOL this is rich: "...identified data security issues concerning certain Yahoo user accounts." Certain...more like all up to that point?

Not by several orders of magnitude.

Re: Yahoo discloses hack of 1B accounts

#249

Post by djsumdog »

ben174 wrote: post #15

This is a time where a decent password manager comes in handy. I can look in my password history to see what my password was in August 2013, and see if that password is still in use anywhere else, then change the password on those sites.

I hate having a secondary system just to get access to my accounts. I use a password algorithm. This ensures I have a unique, easy to remember (or derive), hard to guess password for every account:

http://penguindreams.org/blog/my-accounts-been-hacked-no-it-...

Re: Yahoo discloses hack of 1B accounts

#250

Post by detaro »

Endy wrote: post #153
phantom_oracle wrote: post #89

there's a couple of things that these major providers getting pwned teaches you: 1) their security isn't good just because of their scale/size (that begins to seem more and more like a false-assumption nowadays) 2) migrating your email to a new provider is quite difficult (consider that the average person will have just 1 - or 2 - email accounts and they link EVERYTHING to it) 3) the price of ads/convenience is no lo…

If Yahoo goes down, I won't have email; or at best I'll maybe keep a Zoho. I hate Google's mail interface, I hate the way they make 'conversations' out of discrete emails, and I especially hate their lack of folders. I use GMail begrudgingly at work, and only when necessary, and every time, I look at it and go, "what dipshit ever thought this was a functional way to deal with email?" As a dedicated Windows user, I'm…

You don't like GMail, I understand that (I don't either), but why stick with Yahoo? There are more providers with "old-fashioned, boring" web interfaces...
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