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The problem with the author's paper is that his assumption (and that of, apparently, media organizations, Wikileaks, and others) of DKIM "ensuring non-repudiati

The problem with the author's paper is that his assumption (and that of, apparently, media organizations, Wikileaks, and others) of DKIM "ensuring non-repudiation of emails" is simply wrong. >DKIM provides a life-long guarantee of email authenticity that anyone can use to cryptographically verify the authenticity of stolen emails, even years after they were sent. No, it doesn't. It simply offers an assurance that, at around the time of sending, a given email was mostly likely sent from the server that signed it. It can't prove _anything_ about who actually sent it, because it can't guarantee the ownership of the email account. >For better or for worse, the DKIM authenticity stamp has been widely used by the press, primarily in the context of political email hacks. It’s real, it’s important, and it’s meaningful. There's no _better_ there -- only for worse. It would be better to dispute the validity of using DKIM for non-repudiation of emails than to propagate the lie and ask server operators to publish their expired secret keys.

X6S1x6Okd1st 6y ago
Your conceptions of what is good and bad are not everyone's. When a potentially important email dump is leaked individuals will use any reasonable means to gain information about it's authenticity. Knowing that DKIM headers are on those emails and that the service provider hasn't published those keys changes the question from: "Did you send this email" to "Was your email address compromised at this time?"
- creeble 6y ago
  > “Was your email address compromised at this time?" How would the accused sender be able to prove it was or was not? And is it his or her burden? Yes, individuals will use any reasonable to prove its authenticity. My point is that DKIM is not a reasonable means.
  - X6S1x6Okd1st 6y ago
    For certain scandals just losing control of an email address is enough to cause serious concern. Willfully admitting that control was lost could be a story in and of it's self. Email is not a reasonable means to conduct business, qwerty is a terrible keyboard layout, different countries driving on different sides of the road seems like a really silly thing to do. Just because something isn't reasonable doesn't really hold much sway when it comes to will people use it.
geocar 6y ago
I don't think it needs to be all server operators; It is not difficult for me to believe a Judge could find it "unlikely" that a 2013 email was forged containing a valid Google signature, and I would not want to rely on you being on my jury. If Google were to publish their private keys, I could produce a forgery of my own in my defence. Of course it would be great if people were smarter than they are, but they're not, and I wrote some perl today, so it is hard to tilt at this particular windmill.
LimaBearz 6y ago
Spot on! I use to work for a company that helped Yahoo on the RFC (We were in the email spam space). DKIM is not meant to prove the payload is authentic/un-tampered, merely the person sending the email was authorized to use the domains SMTP server in question. Thats it. DKIM is a one bit in preventing spam. Lets just say it. The emails that sparked all this are looking for something that simply isnt there. They see what they need to see to fit a world view
cakoose 6y ago
> It simply offers an assurance that, at around the time of sending, a given email was mostly likely sent from the server that signed it. It can't prove _anything_ about who actually sent it, because it can't guarantee the ownership of the email account. Not on it's own, but it's a critical step in this chain: 1. DKIM verifies that a message was sent by Gmail. 2. We assume Gmail is careful with its keys. 3. We assume Gmail doesn't forge addresses. 4. Find evidence that links me to that address. Most people will readily grant #2 and #3. Now we just need #4, which can be easy. No, it's not cryptographically verified end-to-end, but it's good enough to convince a court or to convince a respectable news organization to run a story.

X6S1x6Okd1st 6y ago

Your conceptions of what is good and bad are not everyone's. When a potentially important email dump is leaked individuals will use any reasonable means to gain information about it's authenticity. Knowing that DKIM headers are on those emails and that the service provider hasn't published those keys changes the question from: "Did you send this email" to "Was your email address compromised at this time?"

creeble 6y ago
> “Was your email address compromised at this time?" How would the accused sender be able to prove it was or was not? And is it his or her burden? Yes, individuals will use any reasonable to prove its authenticity. My point is that DKIM is not a reasonable means.
- X6S1x6Okd1st 6y ago
  For certain scandals just losing control of an email address is enough to cause serious concern. Willfully admitting that control was lost could be a story in and of it's self. Email is not a reasonable means to conduct business, qwerty is a terrible keyboard layout, different countries driving on different sides of the road seems like a really silly thing to do. Just because something isn't reasonable doesn't really hold much sway when it comes to will people use it.

geocar 6y ago

I don't think it needs to be all server operators; It is not difficult for me to believe a Judge could find it "unlikely" that a 2013 email was forged containing a valid Google signature, and I would not want to rely on you being on my jury. If Google were to publish their private keys, I could produce a forgery of my own in my defence. Of course it would be great if people were smarter than they are, but they're not, and I wrote some perl today, so it is hard to tilt at this particular windmill.

LimaBearz 6y ago

Spot on! I use to work for a company that helped Yahoo on the RFC (We were in the email spam space). DKIM is not meant to prove the payload is authentic/un-tampered, merely the person sending the email was authorized to use the domains SMTP server in question. Thats it. DKIM is a one bit in preventing spam. Lets just say it. The emails that sparked all this are looking for something that simply isnt there. They see what they need to see to fit a world view

cakoose 6y ago

> It simply offers an assurance that, at around the time of sending, a given email was mostly likely sent from the server that signed it. It can't prove _anything_ about who actually sent it, because it can't guarantee the ownership of the email account. Not on it's own, but it's a critical step in this chain: 1. DKIM verifies that a message was sent by Gmail. 2. We assume Gmail is careful with its keys. 3. We assume Gmail doesn't forge addresses. 4. Find evidence that links me to that address. Most people will readily grant #2 and #3. Now we just need #4, which can be easy. No, it's not cryptographically verified end-to-end, but it's good enough to convince a court or to convince a respectable news organization to run a story.