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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

by xbar 6y ago

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?

bluu00 6y ago
your arguement seriously makes the whole _privacy arguement_ seem futile. what about a _telegram_ message?
hyperpape 6y ago
"An accident of the past few years is that this feature has been used primarily by political actors working in a manner that many people find agreeable — either because it suits a partisan preference, or because the people who got “caught” sort of deserved it. But bad things happen to good people too. If you build a mechanism that incentivizes crime, sooner or later you will get crimed on."
- tigger0jk 6y ago
  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 verify their origins? Making real emails and fake emails more similar protects people who have their incriminating emails leaked, but it also harms the defence of people who have fake emails targeting them "leaked". There's a high bar for obfuscating truth and I don't believe this argument meets it.
  - harikb 6y ago
    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.
    - tigger0jk 6y ago
      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 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-keys-can-be-cracked 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.
  - avianlyric 6y ago
    Ah yes, the good old, “If you haven’t done anything wrong, you’ve got nothing to hide” argument. The authoritarians favourite argument for a police state. I guess you’re the type of person that would happily hand over all your personal files to the police on a regular basis as you have nothing to hide.
    - zo1 6y ago
      Not OP. But I would give all my data to the police/government... in an encrypted manner that has guarantees in place that only valid criminal investigations can decrypt. Heck, we do it on some level all the time anyways when it comes to things such as filing taxes, getting married, running companies, enforcing contracts and various other day-to-day benign interactions. At this point, I'm more inclined to believe that "democratic" and "noble" governments and agents are the ones maliciously pushing for "privacy" because it suits their power-maintaining agenda. I'm struggling to find compelling and valid reasons why we can't pursue a general solution that involves us giving all this "private" data to a government entity for legitimate investigations, fraud prevention and crime-solving whilst keeping that data free from abuse.
      - earthboundkid 6y ago
        > I'm struggling to find compelling and valid reasons why we can't pursue a general solution that involves us giving all this "private" data to a government entity for legitimate investigations, fraud prevention and crime-solving whilst keeping that data free from abuse. Because that's not logically possible. It would be nice if it were, but just think about it: if you give data to the government, humans can look at it. Can we ensure that the humans who look at it are good humans? No. Is there some mathematical way of signing and encrypting such that only good humans can look at it? No. Okay, so it's logically impossible to keep bad people out mathematically, but maybe it's a practical problem and it doesn't matter in practice? Except no, there are tons of evil governments (CCP being the most obvious, but pick your poison), and even good governments are subject to the problem that people can bribed and secrets can be stolen if there is sufficient motivation. It's just not compatible with human nature to say "collect all this information on people, but only use it For Good Purposes."
  - scarmig 6y ago
    The world isn't entitled to knowing whether something I'm alleged to have said or done really happened or not. For the people who lack imagination: suppose I'm a public official, and a photograph comes out depicting me doing some kind of "dirty" sexual act. Maybe it's real; maybe it's a deepfake; but if confirmed to be real it certainly would do reputational damage. Non-repudiation by definition prevents me from disavowing it, to no social benefit, and it's an anti-feature, in the sense that the large majority of users would prefer to have the ability to repudiate certain message contents than not. Non-repudiation should be opt-in.
  - thinkharderdev 6y ago
    I don't think the implication that only "bad" people can be blackmailed is valid. You could be blackmailed for being a homosexual in many parts of the US still or doubting the existence of god or having unacceptably conservative political views. We do all sorts of things that are not at all wrong but may carry a significant social or economic cost if they were to be exposed publicly.
    - anfilt 6y ago
      I think people are overlooking this. It can even be worse in other countries. Some of those things (among numerous other things) can lead to death in a few countries.
ChuckMcM 6y ago
Except, as pointed out in the article, over time the ability to crack the underlying key and thus forge such emails becomes very practical. By disavowing the keys it prevents someone from taking a cracked key, forging an email and then "discovering it" for nefarious purposes.
- tzs 6y ago
  Disavowing also protects against key theft or leaks. I'd guess that theft or leaks are probably more likely than cracking, now that the major providers are using long keys.
tptacek 6y ago
Among messaging cryptographers, it's not even an argument. Serious secure messengers have been designed to avoid non-repudiation since OTR. Non-repudiation is a vulnerability: once counterparties have authenticated each other's messages, the legitimate need for authentication is gone; allowing random strangers to authenticate messages concedes information to them. Here, have a link, from 2004: https://otr.cypherpunks.ca/otr-wpes.pdf https://otr.cypherpunks.ca/otr-wpes.pdf
- baobabKoodaa 6y ago
  > once counterparties have authenticated each other's messages, the legitimate need for authentication is gone; allowing random strangers to authenticate messages concedes information to them. As you know, there are many legitimate needs to authenticate messages of strangers. For example, when you order products over the internet, an e-mail of your purchase is often the only proof of what was agreed in the purchase. If there is later a dispute between the buyer and the seller, the email can be used to repudiate lies. In particular, if a third party (like a court) can authenticate the message, the honest party can convince the third party that the dishonest party is being fraudulent. You are exaggerating when you claim that there is no legitimate need to authenticate messages as a third party.
  - tptacek 6y ago
    No, you have confused messaging cryptography with "all of cryptography".
    - baobabKoodaa 6y ago
      You said "there is never a legitimate need to do X". I gave an example of a legitimate need to do X. Your rebuttal is that... I'm confused? Yeah, you're gonna have to be more specific than that if you want to convince anybody.
      - ska 6y ago
        The point was that you pointed out a use case for some sort of cryptographic signing, not for (ab-) using DKIM for this purpose rather than what it was designed for. I don't understand enough about all the issue to really know how I feel about it, but clearly there are trade-offs here that at least argue against expanding the scope.
Alex3917 6y ago
> Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. This. Publishing the DKIM keys would be a huge loss for email archivists and historians in general. E.g. a couple weeks ago Donald Knuth published all of the emails he's sent and received over the last 20+ years of his career[1], without DKIM how would we know that they are authentic? [1] https://library.stanford.edu/blogs/special-collections-unbound/2020/10/don-knuth-email-collection-now-available-research https://library.stanford.edu/blogs/special-collections-unbou...
- tptacek 6y ago
  You can say the exact same thing about all secure messaging, which, after all, has the essential function of keeping documents out of the hands of third parties, including activists and historians. If DKIM upsets you, how do you get your head around disappearing messages?
  - Alex3917 6y ago
    > how do you get your head around disappearing messages? I mean I try to publish most of my interesting email conversations on the web, because every time you have a good email conversation that isn't public it's like taking a $100 bill and lighting it on fire. So I wouldn't ever personally use disappearing messages. Literally the first rule of email is that if you wouldn't want it on the front page of the NYT then you shouldn't send it. The first national scandal involving email was Iran Contra in 1986. People should know by now not to put anything into an email that they wouldn't be comfortable with the entire world knowing. And while privacy is hugely important to individuals and essential for a healthy society, to me rotating DKIM keys feels like it's incentivizing people to use email incorrectly.
    - harikb 6y ago
      Then why don't we design such a system first with a higher level of guarantee first and inform users that this the goal.
kmeisthax 6y ago
This fails the role-reversal test. If Donald Trump had his e-mails leaked in 2016, the blackmailer would likely have extorted a ransom payment from then-candidate Trump. He paid off Stormy Daniels, after all. Nobody would have gotten any juicy e-mail dumps, and some criminals would have had actual leverage over politicians. Just because Hillary Clinton was less shrewd than Donald Trump does not mean that blackmail material is good for us as citizens just because some politicians don't pay ransoms on principle. If you want transparency from your politicians, then you should demand unconditional archival and publication of campaign e-mails. Build transparency into the system. Leakers are not archivists, nor are they journalists. They are leakers, with an entirely different set of motivations and incentives which only sometimes align with journalistic or archival motivations. You as a member of the public will not hear about leaks if the person in possession of those leaked files has successfully extorted or ransomed the politician they came from. In this particular threat model, DKIM does not provide a social benefit to you as a citizen, it provides a monetary benefit to the leaker.
harikb 6y ago
Please read the whole article before jumping into a conclusion about the author, Matthew Green. He sighted two examples where incorrect crypto science affected both a Democrat and a Republican. He is not trying to protect any particular side. He is simply articulating a method by which the key can be invalidated after its intended life time. If you have a technical argument, please explain that.
- 0xy 6y ago
  The timing is extremely suspect, and seems tailor written to protect a single political party.
zajio1am 6y ago
> 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.
- chimeracoder 6y ago
  > 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. It would make a good TV drama plot, but courts don't work this way in real life. If that were the case, courts wouldn't be able to enforce contracts with wet signatures (which are straightforward to forge), or verbal contracts (which are valid contracts and regularly enforced). In practice, you don't need to check DKIM in order to use an email as evidence of a contract, because the courts would more likely just use the many other threats and tools at their disposal to ensure that the email is not fabricated. This is why, even though most contracts are not executed in a cryptographically secure manner, most contract disputes that land before the courts hinge on matters like breach of contract ("we agree on the original terms, but disagree on whether our actions upheld them") or disputes over the intended vs. actual meaning of the contract ("we agree on the text we both signed to, but disagree on the correct interpretation of that text"). Disputes over whether the text of the executed contract is authentic are rare in real life.
  - thinkharderdev 6y ago
    Not to mention that DKIM only validates that en email was sent with particular content from a particular email address. It cannot ensure who was actually sitting at the keyboard composing the email.
    - upofadown 6y ago
      More specifically, DKIM only validates that an email passed through a particular mail server.
  - amadeuspagel 6y ago
dannyw 6y ago
Cryptography should benefit the users.
secondcoming 6y ago
I think he's referring to this? https://www.trumpaccountability.net/ https://www.trumpaccountability.net/
- gowld 6y ago
  That website's owners already abandoned the project under suspicious pretenses of "unity".
  - secondcoming 6y ago
    The biggest pretence is that it's 'abandoned'
codebolt 6y ago
Might have something to do with this: https://www.washingtonexaminer.com/opinion/the-hunter-biden-emails-are-legitimate-and-theyre-not-going-away https://www.washingtonexaminer.com/opinion/the-hunter-biden-...
maest 6y ago
A counter to the non-repudiation of old emails is the fact that people who own their own mail servers can rotate their DKIM keys. So it's already possible for e.g politicians to have their email set up in such a way that they're insulated from leaks. The argument here is more that customers of gmail and other email services are not offered repudiation as a feature.
- gowld 6y ago
  "Rotating keys" isn't the important part. "Publishing keys" is the important part. "Rotating keys" is an implementation requirement of "DKIM with repudiability via eventually-published keys."
  - londons_explore 6y ago
    OP's argument is if you care about this enough, you can set up your own mail server, rotate and publish your own keys on whatever schedule you like.
simias 6y ago
I don't know how I feel about it but I do think it's an interesting argument. The point of DKIM is, first and foremost, to fight spam. The non-repudiation aspect is, as far as I'm concerned, a side effect of DKIM, not a core feature. The more I think about it the more I inch towards agreeing with TFA. If I need my email to be authenticated I can sign them with GPG. If the law enforcement needs to see if I did or did not send an email they can subpoena Google. >Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. Can you expand on this? I can't really come up with a use case that wouldn't be about associating somebody with an email they may want to distantiate themselves from.

by xbar 6y ago

bluu00 6y ago

your arguement seriously makes the whole _privacy arguement_ seem futile. what about a _telegram_ message?

hyperpape 6y ago

"An accident of the past few years is that this feature has been used primarily by political actors working in a manner that many people find agreeable — either because it suits a partisan preference, or because the people who got “caught” sort of deserved it. But bad things happen to good people too. If you build a mechanism that incentivizes crime, sooner or later you will get crimed on."

tigger0jk 6y ago
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 verify their origins? Making real emails and fake emails more similar protects people who have their incriminating emails leaked, but it also harms the defence of people who have fake emails targeting them "leaked". There's a high bar for obfuscating truth and I don't believe this argument meets it.
- harikb 6y ago
  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.
  - tigger0jk 6y ago
    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 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-keys-can-be-cracked 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.
- avianlyric 6y ago
  Ah yes, the good old, “If you haven’t done anything wrong, you’ve got nothing to hide” argument. The authoritarians favourite argument for a police state. I guess you’re the type of person that would happily hand over all your personal files to the police on a regular basis as you have nothing to hide.
  - zo1 6y ago
    Not OP. But I would give all my data to the police/government... in an encrypted manner that has guarantees in place that only valid criminal investigations can decrypt. Heck, we do it on some level all the time anyways when it comes to things such as filing taxes, getting married, running companies, enforcing contracts and various other day-to-day benign interactions. At this point, I'm more inclined to believe that "democratic" and "noble" governments and agents are the ones maliciously pushing for "privacy" because it suits their power-maintaining agenda. I'm struggling to find compelling and valid reasons why we can't pursue a general solution that involves us giving all this "private" data to a government entity for legitimate investigations, fraud prevention and crime-solving whilst keeping that data free from abuse.
    - earthboundkid 6y ago
      > I'm struggling to find compelling and valid reasons why we can't pursue a general solution that involves us giving all this "private" data to a government entity for legitimate investigations, fraud prevention and crime-solving whilst keeping that data free from abuse. Because that's not logically possible. It would be nice if it were, but just think about it: if you give data to the government, humans can look at it. Can we ensure that the humans who look at it are good humans? No. Is there some mathematical way of signing and encrypting such that only good humans can look at it? No. Okay, so it's logically impossible to keep bad people out mathematically, but maybe it's a practical problem and it doesn't matter in practice? Except no, there are tons of evil governments (CCP being the most obvious, but pick your poison), and even good governments are subject to the problem that people can bribed and secrets can be stolen if there is sufficient motivation. It's just not compatible with human nature to say "collect all this information on people, but only use it For Good Purposes."
- scarmig 6y ago
  The world isn't entitled to knowing whether something I'm alleged to have said or done really happened or not. For the people who lack imagination: suppose I'm a public official, and a photograph comes out depicting me doing some kind of "dirty" sexual act. Maybe it's real; maybe it's a deepfake; but if confirmed to be real it certainly would do reputational damage. Non-repudiation by definition prevents me from disavowing it, to no social benefit, and it's an anti-feature, in the sense that the large majority of users would prefer to have the ability to repudiate certain message contents than not. Non-repudiation should be opt-in.
- thinkharderdev 6y ago
  I don't think the implication that only "bad" people can be blackmailed is valid. You could be blackmailed for being a homosexual in many parts of the US still or doubting the existence of god or having unacceptably conservative political views. We do all sorts of things that are not at all wrong but may carry a significant social or economic cost if they were to be exposed publicly.
  - anfilt 6y ago
    I think people are overlooking this. It can even be worse in other countries. Some of those things (among numerous other things) can lead to death in a few countries.

ChuckMcM 6y ago

Except, as pointed out in the article, over time the ability to crack the underlying key and thus forge such emails becomes very practical. By disavowing the keys it prevents someone from taking a cracked key, forging an email and then "discovering it" for nefarious purposes.

tzs 6y ago
Disavowing also protects against key theft or leaks. I'd guess that theft or leaks are probably more likely than cracking, now that the major providers are using long keys.

tptacek 6y ago

Among messaging cryptographers, it's not even an argument. Serious secure messengers have been designed to avoid non-repudiation since OTR. Non-repudiation is a vulnerability: once counterparties have authenticated each other's messages, the legitimate need for authentication is gone; allowing random strangers to authenticate messages concedes information to them. Here, have a link, from 2004: https://otr.cypherpunks.ca/otr-wpes.pdf https://otr.cypherpunks.ca/otr-wpes.pdf

baobabKoodaa 6y ago
> once counterparties have authenticated each other's messages, the legitimate need for authentication is gone; allowing random strangers to authenticate messages concedes information to them. As you know, there are many legitimate needs to authenticate messages of strangers. For example, when you order products over the internet, an e-mail of your purchase is often the only proof of what was agreed in the purchase. If there is later a dispute between the buyer and the seller, the email can be used to repudiate lies. In particular, if a third party (like a court) can authenticate the message, the honest party can convince the third party that the dishonest party is being fraudulent. You are exaggerating when you claim that there is no legitimate need to authenticate messages as a third party.
- tptacek 6y ago
  No, you have confused messaging cryptography with "all of cryptography".
  - baobabKoodaa 6y ago
    You said "there is never a legitimate need to do X". I gave an example of a legitimate need to do X. Your rebuttal is that... I'm confused? Yeah, you're gonna have to be more specific than that if you want to convince anybody.
    - ska 6y ago
      The point was that you pointed out a use case for some sort of cryptographic signing, not for (ab-) using DKIM for this purpose rather than what it was designed for. I don't understand enough about all the issue to really know how I feel about it, but clearly there are trade-offs here that at least argue against expanding the scope.

Alex3917 6y ago

> Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. This. Publishing the DKIM keys would be a huge loss for email archivists and historians in general. E.g. a couple weeks ago Donald Knuth published all of the emails he's sent and received over the last 20+ years of his career[1], without DKIM how would we know that they are authentic? [1] https://library.stanford.edu/blogs/special-collections-unbound/2020/10/don-knuth-email-collection-now-available-research https://library.stanford.edu/blogs/special-collections-unbou...

tptacek 6y ago
You can say the exact same thing about all secure messaging, which, after all, has the essential function of keeping documents out of the hands of third parties, including activists and historians. If DKIM upsets you, how do you get your head around disappearing messages?
- Alex3917 6y ago
  > how do you get your head around disappearing messages? I mean I try to publish most of my interesting email conversations on the web, because every time you have a good email conversation that isn't public it's like taking a $100 bill and lighting it on fire. So I wouldn't ever personally use disappearing messages. Literally the first rule of email is that if you wouldn't want it on the front page of the NYT then you shouldn't send it. The first national scandal involving email was Iran Contra in 1986. People should know by now not to put anything into an email that they wouldn't be comfortable with the entire world knowing. And while privacy is hugely important to individuals and essential for a healthy society, to me rotating DKIM keys feels like it's incentivizing people to use email incorrectly.
  - harikb 6y ago
    Then why don't we design such a system first with a higher level of guarantee first and inform users that this the goal.

kmeisthax 6y ago

This fails the role-reversal test. If Donald Trump had his e-mails leaked in 2016, the blackmailer would likely have extorted a ransom payment from then-candidate Trump. He paid off Stormy Daniels, after all. Nobody would have gotten any juicy e-mail dumps, and some criminals would have had actual leverage over politicians. Just because Hillary Clinton was less shrewd than Donald Trump does not mean that blackmail material is good for us as citizens just because some politicians don't pay ransoms on principle. If you want transparency from your politicians, then you should demand unconditional archival and publication of campaign e-mails. Build transparency into the system. Leakers are not archivists, nor are they journalists. They are leakers, with an entirely different set of motivations and incentives which only sometimes align with journalistic or archival motivations. You as a member of the public will not hear about leaks if the person in possession of those leaked files has successfully extorted or ransomed the politician they came from. In this particular threat model, DKIM does not provide a social benefit to you as a citizen, it provides a monetary benefit to the leaker.

harikb 6y ago

Please read the whole article before jumping into a conclusion about the author, Matthew Green. He sighted two examples where incorrect crypto science affected both a Democrat and a Republican. He is not trying to protect any particular side. He is simply articulating a method by which the key can be invalidated after its intended life time. If you have a technical argument, please explain that.

0xy 6y ago
The timing is extremely suspect, and seems tailor written to protect a single political party.

zajio1am 6y ago

> 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.

chimeracoder 6y ago
> 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. It would make a good TV drama plot, but courts don't work this way in real life. If that were the case, courts wouldn't be able to enforce contracts with wet signatures (which are straightforward to forge), or verbal contracts (which are valid contracts and regularly enforced). In practice, you don't need to check DKIM in order to use an email as evidence of a contract, because the courts would more likely just use the many other threats and tools at their disposal to ensure that the email is not fabricated. This is why, even though most contracts are not executed in a cryptographically secure manner, most contract disputes that land before the courts hinge on matters like breach of contract ("we agree on the original terms, but disagree on whether our actions upheld them") or disputes over the intended vs. actual meaning of the contract ("we agree on the text we both signed to, but disagree on the correct interpretation of that text"). Disputes over whether the text of the executed contract is authentic are rare in real life.
- thinkharderdev 6y ago
  Not to mention that DKIM only validates that en email was sent with particular content from a particular email address. It cannot ensure who was actually sitting at the keyboard composing the email.
  - upofadown 6y ago
    More specifically, DKIM only validates that an email passed through a particular mail server.
- amadeuspagel 6y ago

dannyw 6y ago

Cryptography should benefit the users.

secondcoming 6y ago

I think he's referring to this? https://www.trumpaccountability.net/ https://www.trumpaccountability.net/

gowld 6y ago
That website's owners already abandoned the project under suspicious pretenses of "unity".
- secondcoming 6y ago
  The biggest pretence is that it's 'abandoned'

codebolt 6y ago

Might have something to do with this: https://www.washingtonexaminer.com/opinion/the-hunter-biden-emails-are-legitimate-and-theyre-not-going-away https://www.washingtonexaminer.com/opinion/the-hunter-biden-...

maest 6y ago

A counter to the non-repudiation of old emails is the fact that people who own their own mail servers can rotate their DKIM keys. So it's already possible for e.g politicians to have their email set up in such a way that they're insulated from leaks. The argument here is more that customers of gmail and other email services are not offered repudiation as a feature.

gowld 6y ago
"Rotating keys" isn't the important part. "Publishing keys" is the important part. "Rotating keys" is an implementation requirement of "DKIM with repudiability via eventually-published keys."
- londons_explore 6y ago
  OP's argument is if you care about this enough, you can set up your own mail server, rotate and publish your own keys on whatever schedule you like.

simias 6y ago

I don't know how I feel about it but I do think it's an interesting argument. The point of DKIM is, first and foremost, to fight spam. The non-repudiation aspect is, as far as I'm concerned, a side effect of DKIM, not a core feature. The more I think about it the more I inch towards agreeing with TFA. If I need my email to be authenticated I can sign them with GPG. If the law enforcement needs to see if I did or did not send an email they can subpoena Google. >Non-repudiation over time is a truly powerful property of DKIM'd email for a great many uses outside of blackmail. Can you expand on this? I can't really come up with a use case that wouldn't be about associating somebody with an email they may want to distantiate themselves from.