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I mean, why not tell everyone our password hashes?

theobsidiantower.com

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Re: I mean, why not tell everyone our password hashes?

#61

Post by throwaway2048 »

geofft wrote: post #44
kogepathic wrote: post #9

Earlier quoted context omitted.

> make all password databases public, in an encrypted form That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. Then you'll have a compromised account, the provider won't know, the user won't know. Then the agency would be able to compromise the account a publish whatever they wanted as that identity. Given there are tricks to…

> That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. One, an agency with truly unfathomable resources and techniques is going to be able to get into your network even if you don't post the hashes publicly. Two, all information we have (e.g., the Snowden leaks) implies that NSA/GCHQ/etc. are at best only slightly ahead of acad…

There is a huge difference between actively breaking into every network and accessing all password data, and downloading some public file somewhere, with everybody's passwords in it.

The NSA is going to avoid the former as much as it can, because there is a huge chance they get burned in some way. Anything that they can passively slurp is a huge win for them.

Re: I mean, why not tell everyone our password hashes?

#63

Post by throwaway2048 »

ceejayoz wrote: post #16
kogepathic wrote: post #9

Earlier quoted context omitted.

> make all password databases public, in an encrypted form That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. Then you'll have a compromised account, the provider won't know, the user won't know. Then the agency would be able to compromise the account a publish whatever they wanted as that identity. Given there are tricks to…

> That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. Chances are they already have 'em, from a compromised employee, a zero-day exploit, or a SQL injection hole. Far more likely than them having cracked bcrypt.

I doubt they have exploited every single password DB in existence.

Re: I mean, why not tell everyone our password hashes?

#65

Post by scintill76 »

dsacco wrote: post #47
schoen wrote: post #41

I was kind of disturbed that GitHub publishes every user's public key. https://developer.github.com/v3/users/keys/ This is a different situation and public keys are not directly analogous to password hashes: there isn't a reliable way of cracking public keys in the same sense that there's a semi-reliable way of cracking hashes. But it was still strange and uncomfortable to me that they would reveal this "target" (and…

I'm confused, why would you be disturbed that GitHub publishes every user's public key? This is quite literally the design intention of public keys.

I disagree. The design intention of public keys is not that they should be published along with a mapping to the user's identity, without the user's consent. It's that they may be published, or eavesdropped, without breaking the cryptography itself. See here[0] for the privacy-violating consequences of publishing public keys and identities wholesale.

[0] https://news.ycombinator.com/item?id=10004678

Re: I mean, why not tell everyone our password hashes?

#67

Post by dsacco »

bogomipz wrote: post #57
dsacco wrote: post #43

Earlier quoted context omitted.

> Password "hashes" are generally just cryptographic hashes run multiple times (known as key stretching) 1. Password hashing functions are not regular hash functions run multiple times. This is not only false at a macro level (i.e. we don't just run SHA-2 several times to get something resembling PBKDF2), it's false in terms of core construction. Password hashing functions rely on fundamentally different mathematical…

I'm not familiar with this term "key stretching" is this the same thing as "work factor" in bcrypt/blowfish?

No, "work factor" is a term that (roughly) describes how computationally expensive brute-forcing the digest will be. They're associated terms, but it would be more accurate to think of the work factor as the final result of the key stretching process.

Re: I mean, why not tell everyone our password hashes?

#68

Post by tbodt »

throwaway2048 wrote: post #63
ceejayoz wrote: post #16

Earlier quoted context omitted.

> That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. Chances are they already have 'em, from a compromised employee, a zero-day exploit, or a SQL injection hole. Far more likely than them having cracked bcrypt.

I doubt they have exploited every single password DB in existence.

If they want it, they can get it.

Re: I mean, why not tell everyone our password hashes?

#69

Post by dsacco »

scintill76 wrote: post #65
dsacco wrote: post #47

Earlier quoted context omitted.

I'm confused, why would you be disturbed that GitHub publishes every user's public key? This is quite literally the design intention of public keys.

I disagree. The design intention of public keys is not that they should be published along with a mapping to the user's identity, without the user's consent. It's that they may be published, or eavesdropped, without breaking the cryptography itself. See here[0] for the privacy-violating consequences of publishing public keys and identities wholesale. [0] https://news.ycombinator.com/item?id=10004678

That's not a failure of public key cryptography, that's a failure of the SSH protocol.

As you say, public keys were designed to solve a key distribution problem. Inherent to that problem is the idea that a public key could become, well, public. They solve that problem very well, and there is no intrinsic reason why you shouldn't just publish them because they were intended to be defensible against that very eventuality.

Practically speaking I disagree that GitHub has done anything wrong here - changing habits to diminish the publish-ability of public keys because the SSH protocol exhibits suboptimal behavior encourages further lazy security for the SSH protocol.

We shouldn't tap dance around an SSH-specific problem by claiming that public keys need to be kept secret. That's absurd, we already have private keys. Moreover, it is detrimental to other protocols that rely on publicly verifiable signatures and nonrepudiation to adopt this sort of perspective.

Re: I mean, why not tell everyone our password hashes?

#70

Post by bdamm »

throwaway2048 wrote: post #63
ceejayoz wrote: post #16

Earlier quoted context omitted.

> That is a terrible idea because agencies like the NSA or GCHQ with unfathomable resources and techniques will crack them and never tell anyone. Chances are they already have 'em, from a compromised employee, a zero-day exploit, or a SQL injection hole. Far more likely than them having cracked bcrypt.

I doubt they have exploited every single password DB in existence.

Given what we know about older techniques, it's safe to assume that many intelligence agencies hold zero-days for most popular network and server gear. From my personal experience interacting with some of the people who use these tools, exploiting networks is neither free nor particularly difficult.
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