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Ken Thompson's Unix Password

leahneukirchen.org

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Re: Ken Thompson's Unix Password

#341

Post by kelnos »

TallGuyShort wrote: post #246
CydeWeys wrote: post #168

Earlier quoted context omitted.

You shouldn't be using deeply personal stuff like this for work passwords then. It's very legitimate for a company to want to protect themselves from a massively damaging and costly security/privacy incident by policing against the use of weak passwords.

Just to be clear, I agree, and I think what the person I'm replying to did is totally kosher. But I just think the fact that my password is private should not just be within technical limitations. If you find my password is "hurtmedaddy" I have a reasonable expectation to privacy about that beyond what SHA can and can't protect me from, and I would hope it's not showing up in some weekly report to be shared with IT.…

I personally would not have any expectation that my work passwords are private. I would expect, say, Google to keep my password private, and have internal controls around not letting people see my password, or leak it to the outside. But I'd have no expectation that my boss or IT department didn't have the ability to find out what my password was if they wanted. For strength of security, I really hope they're hashing passwords, but it's well within their rights to try to crack that hash, or log my password as I send it to a webserver the company controls if they want/need to for any reason.

As an imperfect analogy, let's say I write something in a plaintext document, a big rant about how I'm pissed off at one of the executives, and in that rant I make a (not serious, but certainly worrisome) threat against the exec. I foolishly decide to store this document in my company-provided storage on their servers. (Or let's say I stick it in Google Docs in the company's GSuite account.)

Should I have a reasonable expectation of privacy there? I'd say no. I get that some might have the feeling that passwords are different because their entire function is to be private. From a security perspective, yes, I agree. But form a "what you do on company property/resources is visible to the company if they want it to be" perspective, I don't.

Re: Ken Thompson's Unix Password

#342

Post by marcosdumay »

tzs wrote: post #235
colejohnson66 wrote: post #153

Earlier quoted context omitted.

Doubt it. It took 4 days for just one top of the line GPU. Any dedicated attacker will have farms to parallelize it even further. It’s not exactly linear, but with just 4 GPUs (~$4000; well within the reach of any dedicated attacker), that’s one day. Not to mention the fact that GPUs have still been roughly following Moore’s Law in terms of performance. It’s probably safe from the casual attacker who just downloads a…

> If I can crack a DES password in 4 days, I can crack a 3DES password in 12 It's multiplicative, not additive. 3DES is about 2^56 times as difficult to crack as DES. (Not 2^112 times because there is an attack that effectively limits it to twice the effective bits of DES, rather than the three times you might expect at first).

It's more complicated than this, because there are known attacks against 3DES. It's at most 2^28 times more complex, AFAIK, but there are probably better attacks than the few I know.

Re: Ken Thompson's Unix Password

#343

Post by blub »

School-Cotton wrote: post #163

If anyone is curious, the equivalent in modern notation is “1. d4!”. Moving the pawn in front of the queen forward by two spaces. The exclamation point indicates that the annotater believes it to be a particularly strong move (describing a standard move from opening theory that way is a bit tongue-in-cheek).

Yes, "1. d4!" and "1. e4!" are a sort of a Grandmaster joke in chess, showing their strong preference for one the classic competing openings.

Re: Ken Thompson's Unix Password

#344

Post by segfaultbuserr »

tzs wrote: post #235
colejohnson66 wrote: post #153

Earlier quoted context omitted.

Doubt it. It took 4 days for just one top of the line GPU. Any dedicated attacker will have farms to parallelize it even further. It’s not exactly linear, but with just 4 GPUs (~$4000; well within the reach of any dedicated attacker), that’s one day. Not to mention the fact that GPUs have still been roughly following Moore’s Law in terms of performance. It’s probably safe from the casual attacker who just downloads a…

> If I can crack a DES password in 4 days, I can crack a 3DES password in 12 It's multiplicative, not additive. 3DES is about 2^56 times as difficult to crack as DES. (Not 2^112 times because there is an attack that effectively limits it to twice the effective bits of DES, rather than the three times you might expect at first).

> there is an attack that effectively limits it to twice the effective bits of DES

* Meet-in-the-Middle attack.

https://en.wikipedia.org/wiki/Meet-in-the-middle_attack

This attack is surprisingly simple, if you encrypt the message twice by

    ciphertext = encrypt(encrypt(message, key1), key2)
Then,

    decrypt(ciphertext, key2) == encrypt(message, key1)
An important security property all symmetric ciphers should offer is immunity to chosen-plaintext attack, if the attacker controls "message", it shouldn't make the cipher more easy to crack.

But in this case, the attacker can obtain all the 2^56 possible encryption of message by enumerating key1, put it in a lookup table (assume the table-lookup time is O(1)) , then we can try all possible decryption of ciphertext by enumerating key2. Then compare it with the lookup-table for a match, bingo!

If key is 56-bit, the attacker gets 2^56 outputs for the left side, 2^56 outputs for the right side, total number of operations is 2 x 2^56 == 2^57, not 2^112.

To increase the security claim to 2^112, we need triple encryption, not double encryption, thus 2DES is never used.

The idea that simple double-encryption doesn't work because of such a simple attack shocked a lot of newcomers.

Re: Ken Thompson's Unix Password

#345

Post by xhgdvjky »

tandav wrote: post #333
alpb wrote: post #15

Ken Thompson: > congrats. https://inbox.vuxu.org/tuhs/CAG=a+rj8VcXjS-ftaj8P2_duLFSUpmN...

Offtopic. Many teams use mailing lists. That UX always scared me. Is anybody know good tutorials on how to getting started to use this kind of interfaces?

I'd recommend finding a mailing list conversation about a topic you know and then hitting all the buttons (there are only a few). you should be able to figure out the links from context

Re: Ken Thompson's Unix Password

#346

Post by blub »

Zanneth wrote: post #319

Did anyone bother to ask Ken’s permission first before publishing his password on the public internet? Based on his reaction he clearly didn’t mind, but still!

In my opinion this was a pretty crappy thing to do. Password could contain personal and potentially embarrassing information, even if that wasn't the case here.

Re: Ken Thompson's Unix Password

#347

Post by ChuckMcM »

jedberg wrote: post #143

Back when I worked in IT many years ago, one of the things I did each week was run JohnTheRipper on our password file. If it cracked your password, it sent you an email saying your password was weak and you had to change it. If you were in the next week's batch, it emailed you and told you "your password is foobar, which we discovered by cracking the password file, and it is weak. You must change it". Yes, I emailed…

Greg did that at Blekko as well. That is why you always crack the sysadmins password first, and use that. So when they crack it they know that you known that they know.

Re: Ken Thompson's Unix Password

#348

Post by kelnos »

keltor wrote: post #179
CydeWeys wrote: post #169

Earlier quoted context omitted.

This is a bad analogy.

Actually, it's a rather perfect analogy. People have some expectations of privacy and it's not normally considered acceptable to violate this. Sometimes this stuff is untried in court or falls into a definite legal grey area and usually the policy is to err on the side of caution and simply assume that if something is commonly expected to be private, then it's private and should be kept so. If we were investigating a…

It's an absolutely terrible analogy.

First off, putting cameras in restrooms is illegal in most places.

Regardless of that, it boils down to a legitimate company need. Ensuring that users aren't using passwords definitely passes that test. Ensuring that employees aren't sexually harassing other employees also definitely passes that test. Yes, it's unusual that a password tipped people off to bad behavior, but if you see possible evidence of bad behavior, even if it comes from a strange source, you are ethically obligated to look into it. And for a company, not doing so could create legal liability.

Now, bathrooms? Well, for starters, you said "use of work bathrooms being made public". There was nothing "public" about this password case. The password was shared, privately, with HR and the guy's manager. The closest possible bathroom analogy I can think of might be someone reporting to HR that they see someone going into the bathroom multiple times a day, coming out with white powder residue under their nose, and subsequently acting very strangely, like they're on drugs. Which... seems like an entirely appropriate thing to notice and report.

Re: Ken Thompson's Unix Password

#349

Post by boomlinde »

tandav wrote: post #333
alpb wrote: post #15

Ken Thompson: > congrats. https://inbox.vuxu.org/tuhs/CAG=a+rj8VcXjS-ftaj8P2_duLFSUpmN...

Offtopic. Many teams use mailing lists. That UX always scared me. Is anybody know good tutorials on how to getting started to use this kind of interfaces?

A decent email client will display these as a foldable hierarchy, sort of like HN or Reddit's posting interface, just with the body of the posts hidden. With that and full text search it's not so hard. It's the web interfaces that are a bit bulky.

Re: Ken Thompson's Unix Password

#350

Post by PacketPaul »

blub wrote: post #346
Zanneth wrote: post #319

Did anyone bother to ask Ken’s permission first before publishing his password on the public internet? Based on his reaction he clearly didn’t mind, but still!

In my opinion this was a pretty crappy thing to do. Password could contain personal and potentially embarrassing information, even if that wasn't the case here.

Now I know his chess move.
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