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Ok Google: please publish your DKIM secret keys

blog.cryptographyengineering.com

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Re: Ok Google: please publish your DKIM secret keys

#241

Post by Quarrel »

shinigami wrote: post #166
zajio1am wrote: post #73

Earlier quoted context omitted.

> Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. Exactly. If one enters into an contract using an e-mail, then DKIM can be used as a proof to the court of law that the contract was accepted by both sides.

Entering an contract via an email is a ridiculous idea from the start.

wtf? it happens all the time.

I've raised VC money based on emailed contracts, bought businesses based on them, bought domain names.

It is incredibly standard and legal (in almost all of the jurisdictions I've worked in, which is a lot).)

Re: Ok Google: please publish your DKIM secret keys

#242

Post by hamburglar »

baobabKoodaa wrote: post #240
hamburglar wrote: post #221

Earlier quoted context omitted.

> Ok, my GPG example was wrong. And yes, you got me, I'm not a professional cryptographer. But can you address the point? You said "once counterparties have authenticated each other's messages, the legitimate need for authentication is gone". I provided a counter-example ... I think the person you're talking to thinks this is very obvious and thus isn't stating it explicitly, but in the special case where you want an…

> the sender should just add non-repudiation to it in the form of a signature that's intended for that. Simple. Ok, but this does not magically happen if Google publishes and rotates their DKIM keys. People will continue to use email for everything, but now emails can no longer be authenticated by third parties.

I think the entire point is that non-repudiation shouldn't just magically happen unless intended, so yes, this is by design, and anyone who wants to send a signed email should explicitly send a signed email.

Re: Ok Google: please publish your DKIM secret keys

#243

Post by lxgr »

Red_Leaves_Flyy wrote: post #236
lxgr wrote: post #234

Earlier quoted context omitted.

> As you know, there are many legitimate needs to authenticate messages of strangers. Absolutely, but this should be an opt-in feature (and not provided server-side, at that).

>this should be an opt-in feature (and not provided server-side, at that). Why?

It just feels like the baseline expected behavior of a communications system to me that makes no explicit claims otherwise.

Legal signatures are heavily ritualized (blue/black ink only, initial here and sign there etc.) in most societies for good reason – it makes the signer stop for a moment and reconsider what they are doing, if the document they are signing is truly aligned with their intentions and so on.

As another analogy/food for thought: We have the technical means to record every conversation we ever have, digital or analog, public or private. Should we? If not, why not?

Re: Ok Google: please publish your DKIM secret keys

#244

Post by nullc »

newacct583 wrote: post #213
drewbug wrote: post #193

Earlier quoted context omitted.

https://github.com/robertdavidgraham/hunter-dkim/blob/main/M...

Interesting, thanks. Odd that this data was never part of the published record from the Post, and that Graham's source is apparently secret? Curious what you make of that? If the Post had it, they'd surely have released it. I guess it's sort of academic at this point, but it does point to a few different actors pushing this story in different directions.

> If the Post had it, they'd surely have released it.

It's extremely rare for journalists in traditional media to publish email headers, even when people are accusing messages of being inauthentic and the DKIM would go a long way towards certifying them and when people are begging for them. I think I'm aware of only one other instance, though I've personally begged journalists for headers multiple times even in some cases where I was a subject of the article and not some random nobody.

From the perspective of protecting sources it's probably good advice to avoid publishing any kind of opaque header-stuff. But also, most readers wouldn't know what to do with the information and -- less charitably-- publishing evidence moves away from the framework where readers accept the reporters word on blind faith.

Your position was entirely understandable: I declined to link to the repo or the two flagged HN threads about it, though I considered it, because I thought it would increase the risk that my comment would get flagged. I think your reply had the surprising consequence of making a really good example at how effective the suppression of info like this is at distorting the public discourse.

Re: Ok Google: please publish your DKIM secret keys

#245

Post by feanaro »

hpoe wrote: post #18

So the author's central thesis essentially seems to boil down to that leaked emails were able to be cryptographically verified, because of DKIM and so we should prevent that so people can't use email to blackmail politicians? Ultimately I prefer the more information that we can get on politicians available. It seems to me that especially when an elected official has something they don't want others to know about that…

A good blackmail attempt could then be devastating for you, on the other hand.

Re: Ok Google: please publish your DKIM secret keys

#246

Post by baobabKoodaa »

tptacek wrote: post #219
baobabKoodaa wrote: post #184

Earlier quoted context omitted.

Here is the actual quote: "once counterparties have authenticated each other's messages, the legitimate need for authentication is gone". Yes I used quotes in the "do X" sentence, but nobody will mistake it for a literal quote, because it contains "X" in place of the actual thing. Anyway, do you think there is something wrong with my characterization of that statement?

Yes, because it ignores the sentence that precedes it.

> Yes, because it ignores the sentence that precedes it.

This sentence? "Serious secure messengers have been designed to avoid non-repudiation since OTR." I don't see how this sentence supposedly alters the meaning of the sentence that comes after it? At this point it seems like you just want to sow confusion. If I had misinterpreted your words in some way, you could have clarified the misunderstanding like 10 times by now. Instead, you choose to reply in snarks like saying I'm confused, or asking me to read your comment again. I don't think there's any misunderstanding. You took an extreme position that didn't hold up to scrutiny, and you don't want to defend your position or back down, so you just reply in snarks instead. If there is some kind of misunderstanding, please do go ahead and explain what the misunderstanding is.

Re: Ok Google: please publish your DKIM secret keys

#247

Post by tigger0jk »

harikb wrote: post #74
tigger0jk wrote: post #67

Earlier quoted context omitted.

People who are protected from blackmail by email repudiation are by definition people who have incriminating emails. Maybe everyone had skeletons in their closet, but if you have email proof of skeletons I'm starting to wonder if you're such a good person. Also there's an argument that "good people" can be blackmailed for INVENTED misconduct, but wouldn't such fake emails be more convincing without the ability to ver…

Please read the whole article. If it only takes a "few hours" to create incriminating "evidence" (read, something that didn't exist) - it must be clearly proclaimed as such to the world.

I believe you are referring to this quote (correct me if not): "In fact, in the early DKIM configurations were kind of a joke: mail providers chose DKIM signing keys that were trivial for motivated attackers to crack. Back in 2012 a security researcher named Zachary Harris pointed out that Google and several other companies were using using 512-bit RSA to sign DKIM. He showed that these keys could be “cracked” in a matter of hours on rented cloud hardware, and then used these keys to forge emails from Larry and Sergey.

Providers like Google reacted to the whole “Larry and Sergey” embarassment in the way you’d expect. Without giving the implications any serious thought, they quickly ramped up their keys to 1024-bit or 2048-bit RSA. This stopped the forgeries, but inadvertently turned a harmless anti-spam protocol into a life-long cryptographic authenticity stamp — one that can be used to verify the provenance of any email dump, regardless of how it reaches the verifier."

Note that the "few hours" attack here is only relevant if they were using easily crackable 512-bit keys. The author of this article suggests (and I agree) that the 1024 or 2048 bit RSA keys are not easily crackable. (see https://crypto.stackexchange.com/a/42830)

Maybe you are suggesting that someone could sign emails using the old crackable 512-bit keys. And they could, although we should disregard this as "not verification" given the weak keys. The article links to https://github.com/robertdavidgraham/hunter-dkim#short-dkim-... - which verifies an email using a since-rotated 2015 key (which was 2048 bits), although that github erroneously states that Google was using 1024 bit before that (they were using 512).

I would concede that the notion of "sometimes we should disregard some DKIM verifications based on the key length" is not easy to grasp and that email verification stories in the media could become muddier and harder to present. I would hope that interviewing experts gets you a reasonable estimation of how likely an email is to be legitimate.

Re: Ok Google: please publish your DKIM secret keys

#248

Post by schoen »

bartvk wrote: post #224
shinigami wrote: post #166

Earlier quoted context omitted.

Entering an contract via an email is a ridiculous idea from the start.

I don't know about your country, but in mine (The Netherlands), it is a completely and utterly valid way to enter a contract. Actually, you are free to enter a contract in any way possible. It is vormvrij (translated: form-free). Excluded is the purchase of a house, as far as I know. But for the rest, you are free to come to an agreement via WhatsApp, Facebook, email, or a scrawl on a piece of paper.

In the U.S., many contracts (but not all) can in principle by default be oral and still be enforceable by law.

https://smallbusiness.findlaw.com/business-contracts-forms/w...

Re: Ok Google: please publish your DKIM secret keys

#249

Post by anticristi »

bartvk wrote: post #224
shinigami wrote: post #166

Earlier quoted context omitted.

Entering an contract via an email is a ridiculous idea from the start.

I don't know about your country, but in mine (The Netherlands), it is a completely and utterly valid way to enter a contract. Actually, you are free to enter a contract in any way possible. It is vormvrij (translated: form-free). Excluded is the purchase of a house, as far as I know. But for the rest, you are free to come to an agreement via WhatsApp, Facebook, email, or a scrawl on a piece of paper.

Same in Sweden. "Are you okey with paying extra for X?" "Yes, please go ahead."

And that's how a new contract gets signed! No need to fly someone 1500km just for that.

Re: Ok Google: please publish your DKIM secret keys

#250

Post by codebolt »

xbar wrote: post #25

I think this is a shameful argument. Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. Calling for the ability to remove it during the years 2016-2020 in order to "protect politicians from blackmail" is not only of deeply questionable value but of suspect motivation. Who is the author interested in protecting?

Might have something to do with this:

https://www.washingtonexaminer.com/opinion/the-hunter-biden-...

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