291–300 of 433 posts
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Counter-example example: I've been an expert witness in court to prove an email was a forgery; using DKIM.
It'd be funny if we were working together and just telling the same story behind our aliases.
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If you publish DKIM keys, you don't have to convince anybody that you were targeted by someone who stole your password, because your stolen email spool no longer reveals to attackers the authenticity of your emails, which is what you as a user want.
But you need to convince someone that someone targeted you and used the published key to forge an email. Where is the difference?
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I never suggested that Yahoo uses 512bit keys, that's a misunderstanding. The article clearly states that Yahoo is one of the 3 clients that didn't reject 512bit keys the way they should per RFC. Yahoo Mail inbox users are vulnerable _receivers_ of spoofed emails.
remember when yahoo mail was the first one to implement DKIM validation and then all mailing list owners added a footer telling their subscribers not to use yahoo mail because it was broken, instead of calling their mailing list providers to upload a key? yeah nobody remembers, but yahoo probably do. i doubt they will err on the side of security again.
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> it's a grave privacy violation. I'm missing something here. DKIM mostly proves an email from person@from.me was sent by a server @from.me controls. There is also a bloody great audit trail inside of the email with together with SPF can do a pretty good job of proving the same thing. I'm struggling to see how an email sent to me, that presumably was always intended to be readable by me could suddenly become a privac…
It's nobody else's business whether the emails in your inbox are valid or not, and that's basically all non-deniable DKIM signatures do: durable secure verifiable DKIM signatures are "security feature" with real-world value exclusively for attackers .
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But you need to convince someone that someone targeted you and used the published key to forge an email. Where is the difference?
No you don't. You just say "that email is fake and you can't prove otherwise", and you're right. What's almost more important is: there is no reason not to give users that affordance. They literally do not benefit from the non-repudiability of their email archive. The OTR paper got this right 20 years ago, and in the process basically created the entire field of secure messaging. It is wild to see people argue agains…
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No you don't. You just say "that email is fake and you can't prove otherwise", and you're right. What's almost more important is: there is no reason not to give users that affordance. They literally do not benefit from the non-repudiability of their email archive. The OTR paper got this right 20 years ago, and in the process basically created the entire field of secure messaging. It is wild to see people argue agains…
I think here is where the problem isn't purely a technical one anymore. You're right that, from a legal perspective, there is a difference as the burden of proof would now be on someone else. But, if this actually matters or not, depends entirely on the situation. If you're a criminal trying to get away with something then the change in the burden of proof is all you need. If instead you're a politician trying to avo…
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Isn't deniability at odds with DKIM's goal? What would be the point of setting DKIM then? Sure, it helps with spam scores. But most companies rely on a major email provider to send emails, so maybe they wouldn't have deliverability issues anyway?
Do take a look at the blog post I cited above, where I go into this in loads of detail. The TL;DR is that DKIM only needs to ensure origin authenticity for the time it takes to deliver an email, which is usually a few hours or a day at most. The unintentional problem DKIM is causing is that it actually provides non-repudiation for many years. Those signed emails can sit in someone's mailbox for years, then get stolen…
> Reasonable people (e.g., high-integrity newspapers, courts of law) will say "how can we trust that these stolen emails are authentic given that there's no chain of custody?" DKIM signatures nearly answer that question, which makes stolen emails much more valuable than they would be otherwise.
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It's nobody else's business whether the emails in your inbox are valid or not, and that's basically all non-deniable DKIM signatures do: durable secure verifiable DKIM signatures are "security feature" with real-world value exclusively for attackers .
If you’re under Rule 26 discovery or disclosure requirements, it absolutely might be my business whether emails in your client are valid, but I suppose you could classify opposing counsel as an “attacker,” so you’re not wrong.
I don't understand why didn't Yahoo fail due to SPF check failure.
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It's also only true so long as we don't discover more efficient ways of factoring large numbers. We haven't come up with any dramatic improvements lately, but it's always possible that something will come up. Symmetric crypto systems like AES are on much firmer ground, as they don't depend as heavily on the difficulty of any single mathematical problem.
By "lately" you mean...