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Yahoo discloses hack of 1B accounts

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Re: Yahoo discloses hack of 1B accounts

#261

Post by user5994461 »

ausjke wrote: post #24

I'm speechless. More and more are migrating to cloud these days, I expect more and more epidemic leakage will come. I host everything myself except for email, which is always a headache but contains more private info than all others I manage combined. Maybe it is time to run a small email server again but it is easily said than done, gosh please give me something like a working PGP or whatever for safe emails(PGP is…

> More and more are migrating to cloud these days, I expect more and more epidemic leakage will come.

Why? Couldn't isn't relevant to security.

If anything, it makes it easier to configure firewalls and rights, so it's easier to put security in place.

Re: Yahoo discloses hack of 1B accounts

#262

Post by throwaway1X2 »

jrockway wrote: post #236
sqldba wrote: post #230

Technically; no. Bureacratically; maybe. Given the skill and self direction of offshore workers; impossibly.

You've somehow managed to turn a bug report into a soundboard for your racist insecurities. Impressive. In a sad way.

Yes, 'offshore' is a race. Every critique is a racism.

Coming from said 'offshore' (at least in regards to the US), I see that 'quality' people work remotely for monies comparable to the onsite workers, launch startups, et cetera. If you outsource to the offshore for the costs, guess what, you get lesser quality for the said cost. Nothing racist in that, but I understand your position - a SJW to every household!

Re: Yahoo discloses hack of 1B accounts

#263

Post by leereeves »

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…

Most people here don't seem to understand the difference between collision and preimage attacks. So they're overreacting to the fact Yahoo used MD5.

Storing unsalted passwords, however, would be a huge mistake, if Yahoo did so as someone here claimed.

There are precomputed lookup tables for the unsalted hashes of many, many passwords (both MD5 and more secure hashes) and cracking unsalted passwords is simply a database lookup.

Re: Yahoo discloses hack of 1B accounts

#265

Post by noonespecial »

cm2187 wrote: post #191
noonespecial wrote: post #184

Earlier quoted context omitted.

The problem is in collisions. Md5(password) can yield the same result for many different values of password so simply bcrypting that result means that you start with a restricted possibility space. So less secure. Punts the question to how much less secure. Seems to me it would still be worth it to do and then all new passwords going forward are done correctly.

Agree, but a collision even for md5 is a relatively rare event. When brute-forcing the bcrypt hash, this would reduce the attempts you would need to try against a given hash, but only by a very small factor. With a reasonable work factor, I would assume it would still make a brute force attack impractical at scale. I didn't do the test, but I'd expect that there wouldn't be more than a handful of collisions for the m…

Very nice. Thanks for that. So yes, this is likely the thing to do in this situation.

Re: Yahoo discloses hack of 1B accounts

#266

Post by manarth »

leereeves wrote: post #226
manarth wrote: post #140

Earlier quoted context omitted.

You can only rehash if you have the plaintext password There are techniques to rehash, even without the plain-text password, and without the user having to login to trigger a rehash. Drupal 7 used such a technique for upgrades from Drupal 6, migrating from MD5 to a salted sha512 hash, but it's not an uncommon technique. The old passwords are stored as MD5 hashes in the databases. The MD5 hash is processed through the…

> hash = sha512(salt + MD5(password)) Passing the password through MD5 reduces the complexity to 128 bits, you can't get that back. So the security level is not the same, though it may be resistant to some attacks on MD5. And it's probably not important for most people, since there are less than 2^56 eight character ASCII passwords.

  > "Passing the password through MD5 reduces the complexity to 128 bits, you can't get that back."
Assuming that the new hash is secure (and sha512 is generally agreed to be secure), then, given a specific sha512 hash, the original MD5 hash can only be determined via rainbow tables, which is a Big-O operation. Even though entropy is reduced, it's still a significant work to determine the original MD5 hash (significant in this instance being longer than the heat-death of the Sun, given current extrapolations of computing performance).

Attacks against MD5 are based around knowing the original MD5 hash. In this instance, the original MD5 hash is unknown, so there is no mathematical shortcut to finding a collision.

Re: Yahoo discloses hack of 1B accounts

#267

Post by jsjohnst »

cm2187 wrote: post #191
noonespecial wrote: post #184

Earlier quoted context omitted.

The problem is in collisions. Md5(password) can yield the same result for many different values of password so simply bcrypting that result means that you start with a restricted possibility space. So less secure. Punts the question to how much less secure. Seems to me it would still be worth it to do and then all new passwords going forward are done correctly.

Agree, but a collision even for md5 is a relatively rare event. When brute-forcing the bcrypt hash, this would reduce the attempts you would need to try against a given hash, but only by a very small factor. With a reasonable work factor, I would assume it would still make a brute force attack impractical at scale. I didn't do the test, but I'd expect that there wouldn't be more than a handful of collisions for the m…

I've done it before on a 1 billion word / password list and didn't get any collisions.

Re: Yahoo discloses hack of 1B accounts

#268

Post by Helmet »

234dd57d2c8db wrote: post #254
jrockway wrote: post #236

Earlier quoted context omitted.

You've somehow managed to turn a bug report into a soundboard for your racist insecurities. Impressive. In a sad way.

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

Given the context, you know damn well what he means - it's coded speech and I refuse to believe that you're that naive.

Re: Yahoo discloses hack of 1B accounts

#269

Post by pbhjpbhj »

Endy wrote: post #123
cm2187 wrote: post #107

Earlier quoted context omitted.

But it's not like if we didn't have a pretty much continuous stream of major data leaks for the past 5 years. Surely yahoo engineers occasionally open a newspaper...

From everything I've read, the engineers did. The problem was that the security team had to go head-to-head with the budget team. And unfortunately, the budget team won - since the upper levels didn't feel that the IT security salaries were a necessary expenditure. And beyond that, there was concern that making people actually change their passwords regularly and requiring anything like security in said passwords was…

> The problem was that the security team had to go head-to-head with the budget team. //

Wouldn't engineers at such a big corp whistle-blow such incompetent decision making?

Apparently [1] they had a $1.37B net income in 2013. Given using bcrypt with a Blowfish hash and salting was pretty much a de facto standard by that point (I think that's what Wordpress were doing, hardly revolutionary security work) it seems the relative cost for Yahoo was approximately zero.

All I can imagine is that those in control were asked to leave the system open for government snooping? Why else would engineers working there not [anonymously] bring this to press attention - "hey, Yahoo security amounts to a piece of sticky tape holding a bank-vault shut".

- - -

[1] http://www.marketwatch.com/investing/stock/yhoo/financials#

Re: Yahoo discloses hack of 1B accounts

#270

Post by ausjke »

ausjke wrote: post #24

I'm speechless. More and more are migrating to cloud these days, I expect more and more epidemic leakage will come. I host everything myself except for email, which is always a headache but contains more private info than all others I manage combined. Maybe it is time to run a small email server again but it is easily said than done, gosh please give me something like a working PGP or whatever for safe emails(PGP is…

"Based on further analysis of this data by the forensic experts, we believe an unauthorized third party, in August 2013, stole data associated with a broader set of user accounts, including yours. "

"The stolen user account information may have included names, email addresses, telephone numbers, dates of birth, hashed passwords (using MD5) and, in some cases, encrypted or unencrypted security questions and answers. "

I'm a paid premium member for Yahoo's service for many years, I would like to join somebody else to sue the hell out of Yahoo.

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