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Yahoo discloses hack of 1B accounts

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Re: Yahoo discloses hack of 1B accounts

#381

Post by duskwuff »

rev_bird wrote: post #241
duskwuff wrote: post #162

Earlier quoted context omitted.

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…

> 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.

Very early MD5 collision attacks were even weaker, actually: given nothing, it was possible to find a pair of arbitrary garbage strings which had the same hash as each other. It wasn't until later that it became possible to pick what the strings would "look like".

> Are these "crafted collisions" generated by modifying string A and string B, until a collision pops out?

Generally speaking, yes.

> If that's the case... what's everyone freaking out about?

The issue with using MD5 as a password hash function actually has nothing to do with collisions. That's a red herring. :) The real problem is that using any fast and/or unsalted hash function for passwords is unsafe!

A fast hash function is unsafe because it makes it easy to generate a bunch of potential passwords, calculate their hashes, and look for a match.

An unsalted hash function is unsafe because it makes it possible to build a "rainbow table" of all possible passwords and their hashes, and look up password hashes in that table.

As used in this situation, MD5 is both fast and unsalted.

Re: Yahoo discloses hack of 1B accounts

#383

Post by badsock »

ra1n85 wrote: post #293
badsock wrote: post #274

Earlier quoted context omitted.

I'm sure they meant to say xenophobic.

Yeah, just keep throwing those out there...one is bound to stick, right?

If you're a priori judging the quality of a someone's work based exclusively on the nation of origin, that falls within the dictionary definition of xenophobia.

You can choose to not like the connotations of the word, but that's just your choice. Definitions of words are real.

Re: Yahoo discloses hack of 1B accounts

#386

Post by daveguy »

cookiecaper wrote: post #357
b2600 wrote: post #349

Earlier quoted context omitted.

If your statement is accurate, why offshore the work?

He came recommended by someone who had used him before. His country of residence was not relevant to our hiring decision.

I wish I could upvote this thread 100x. Everyone should have to deal with global competition and everyone competitive should have commiserate compensation. Unfortunately there are barriers to that (informational and transactional).

I also think everyone uncompetitive should get basic income.

Re: Yahoo discloses hack of 1B accounts

#387

Post by normaljoe »

jsjohnst wrote: post #31
niftich wrote: post #14

> August 2013 > hashed passwords (using MD5) I don't even know what to say. > investigating the creation of forged cookies that could allow an intruder to access users' accounts without a password. Based on the ongoing investigation, we believe an unauthorized third party accessed our proprietary code to learn how to forge cookies How is this possible? Aren't most auth cookies just a session ID that can be used to lo…

1) As Yahoo "upgraded" all password storage in UDB (where all login / registration details are stored) to be bcrypt before 2013, I'm curious how this was possible. 2) Yahoo doesn't use a centralized session storage. If you know a few values (not disclosing the exact ones) from the UDB, it's theoretically (guess not so theoretical now) possible to create forged cookies if you steal the signing keys. To my knowledge, t…

I'm guessing by your handle I know who you are :). Ex-Yahoo super chat moderating guy here, which should let you know me.

Wouldn't the upgrade require the accounts to actually login to migrate password? Last I was at Yahoo there was at least 3B junk accounts in UDB. With out knowing details I am guessing that many of the "compromised" accounts fall into that bucket.

I get that membership can't just trash junk accounts but marketing was very aware of them. Paranoids also can't just say a compromised junk account is not a compromise, they are too paranoid for that.

This unfortunately sounds bad PR wise, with little knowledge of actual impact. On the flip side I'm pretty sure I am not on the radar of the state actor since they would more then likely be looking at their own.

Re: Yahoo discloses hack of 1B accounts

#388

Post by daveguy »

MarkMc wrote: post #361
234dd57d2c8db wrote: post #254

Earlier quoted context omitted.

... "offshore workers" are not a race. You realize offshore workers could be the same race as the person posting right?

I don't know whether sqldba was suggesting something racist, but I would say it is not necessary to identify a particular race hint at a racist viewpoint. When Ronald Regan said "welfare queen", did he mean to imply "black woman on welfare"? If I write, "Middle-eastern people are lazy" do I mean to imply "Arabs are lazy - but not necessarily Jews"? I also wonder whether you can have a racist view of your own race. Fo…

Yes. You can be racist against your own race.

Re: Yahoo discloses hack of 1B accounts

#389

Post by Buge »

raverbashing wrote: post #221
Arubis wrote: post #165

Fittingly, attempting to change my password to a 32-character random string generated by 1Password returns an error that the password "cannot contain my email or username", regardless of the contents of that random string (I tried several). It does, however, _happily_ accept `passwordpassword` and cheerily move along to confirming that my recovery email account from 2003 is still valid.

Just leave it at passwordpassword, it will be leaked eventually anyway Strong passwords that need to be memorized shouldn't be wasted on security bozos

Why do you assume the password would be leaked eventually? Usually hashes are leaked (as in this case), not passwords.

Re: Yahoo discloses hack of 1B accounts

#390

Post by syntheticnature »

Arubis wrote: post #165

Fittingly, attempting to change my password to a 32-character random string generated by 1Password returns an error that the password "cannot contain my email or username", regardless of the contents of that random string (I tried several). It does, however, _happily_ accept `passwordpassword` and cheerily move along to confirming that my recovery email account from 2003 is still valid.

I've run into off-by-one issues in password length requirements in the past, so if 32 characters is the stated maximum it might only be capable of 31 on the validation side.
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