4 ms·

Breaking a 512-bit key for a good demonstration is very valuable security research, even if it's been done before. It's also legit to call out "Hey, here's a li

Breaking a 512-bit key for a good demonstration is very valuable security research, even if it's been done before. It's also legit to call out "Hey, here's a list of folks still using 512 bit, they should move off." ... but for me, actually cracking a real-world in-use key crosses an ethical line that makes me uncomfortable. IANAL but it might even be criminal. Just seems a bit unnecessary.

tptacek 2y ago
I don't think there's a way to make it criminal, any more than publishing a vulnerability that got you code execution on their servers could be. Actually exploiting it, of course, would be.
- colmmacc 2y ago
  I think many in cryptography would see cracking a key as a precondition to "actually exploiting it" ... because you've only gotten a cryptographic secret, not "actual data". But I think many others, and many in law enforcement, will see cracking a key as "actually exploiting it". You've exploited the cracking vulnerability to target a particular key, is how they'll see it. Law enforcement also have a natural incentive to want possession of harm-adjacent paraphernalia to carry substantial liability. I think they have a point; that key is private data, and there's a reason people lock keys up in KMSs and HSMs; they can have a large blast radius, and be hard for companies to revoke and rotate. Importantly, a compromise of a key will often trigger notification requirements and so now it is a breach or an incident, in a way that a good faith security vulnerability report is not. To make an extreme example; if you were to crack an important key for a government agency, good luck with that is all I'll say. I sure wouldn't.
  - tptacek 2y ago
    The US law most at play in criminal prosecution of computer usage is CFAA, and a clear CFAA predicate is intentional access to a protected computer (18 USC 1030(a)(2)). This distinction is what makes vulnerability research on things like Chrome vulnerabilities generally safe (as long as you don't knowingly spirit exploits to people who are actually attacking people), while vulnerability research on other people's websites (looking for SQLI and SSRF) is risky. The CFAA has a clause about "trafficing in passwords or similar information" (18 USC 1030(a)(6)), but the mental state requirements are very high: that trafficking has to be knowing and with intent to defraud (that intent will be something prosecutors will have to prove at trial). There might be some state law somewhere that makes this risky, but virtually every hacking prosecution in the US anyone has heard of happens under CFAA. I'm not a lawyer, but I've spent a lot of time with CFAA, and I think cracking DKIM keys is pretty safe.
    - colmmacc 2y ago
      By this interpretation it would be perfectly legal to abuse a wifi encryption vulnerability to spy on your neighbors, because that doesn't involve accessing a computer of theirs. My understanding, and IANAL, is that decrypting things that aren't yours is a bad idea and is covered mainly by electronic communications and wire acts, e.g. U.S. Code § 2511 and others.
      - tptacek 2y ago
        A wifi encryption vulnerability that required you to interact with a base station or remote computer would implicate CFAA. A wifi encryption vulnerability that allowed for pure passive interception --- a devastating flaw in 802.11/WPA3 --- might not actually violate any federal law directly. There are probably state laws (I believe Michigan has one) that implicate packet sniffing directly (they were problematic in the early oughts for security researchers). Worth remembering: when CFAA was originally passed, an objection to it was "we already have laws that proscribe hacking computers"; the fraud statutes encompass most of this activity. CFAA's original motivation was literally WarGames: attacks with no financial motivation, just to mess things up. So even without statutory issues, breaking an encryption key and using it to steal stuff (or to gain information and ferry it to others who will use it for crimes) is still illegal. Your guess is as good as mine about whether ECPA covers wifi sniffing. But: presuming you obtain an encryption key through lawful means, ECPA can't (by any obvious reading) make cracking that key unlawful; it's what you'd do with the key afterwards that would be problematic.
        colmmacc 2y ago
        My understanding of the ECPA and other acts is that you can't intercept, decode, or receive by other intentional means any information or communications that aren't "generally accessible" without permission. It's pretty broad and doesn't care about the "how". Private keys are not "generally accessible" and my concern is that the authorities will see cracking the key itself as issue enough, and unlawful. If a security researcher triggers painful breach notifications, which could well happen for a compromised private key, I don't think it's unthinkable at all that an upset target will find a DA who is happy to take this interpretation. I don't think this specific DKIM case is particularly high-risk, but I still wouldn't do it without permission from the key holder.
michaelmior 2y ago
I am also not a lawyer, but I would suspect it's not criminal to crack a real-world in-use key if you do so using only publicly available information and you don't actually do anything with the result.
- colmmacc 2y ago
  Let's say you local coffee shop is featured in a local news piece and the blithe owner happened to get photographed holding the store key. That's now easy to clone from public information. Would you be comfortable actually doing it? Reporting the issue is fine - "Hey you should rekey your locks!". Actually making a clone of the key, and then showing "hey it fits" will get you more traction more quickly ... but there's also plenty of Police Departments who might well arrest you for that.
  - michaelmior 2y ago
    > showing "hey it fits" That's exactly what I meant in terms of not actually doing anything with the result. That said, it's obviously somewhat different with a physical key than a cryptographic key.
phoe-krk 2y ago
> for me, actually cracking a real-world in-use key crosses an ethical line that makes me uncomfortable They've contacted the company with the vulnerability and resolved it before publishing the article - search the original article for the substring "now no longer available". Usually, you demonstrate that an online system is vulnerable by exploiting that vulnerability in good faith, documenting the research, and submitting it for review. It does not matter if you're cracking an encryption scheme, achieving custom code execution for a locked-down game console, proving that you can tamper with data in a voting machine, or proving that you can edit people's comments on a Google Meet Q&A session - the process is the same. If you say something's vulnerable, people can shrug it off. If you say and prove something's vulnerable, the ability to shrug it off shrinks. If you say and prove something's vulnerable and that you'll publish the vulnerability - again, using the industry standard of disclosure deadlines and making the vulnerability public after 60-or-so days of attempting to contact the author - the ability to shrug it off effectively disappears.
- colmmacc 2y ago
  I read the article, and I don't think it changes it. If you crack someone's key, they might be well within their rights to pursue a criminal prosecution. Of course it would also have a Streisand effect and there's reasons not to, but I personally wouldn't allow or recommend a security researcher to do it. It's needlessly risky. In general, subverting security and privacy controls tends to be illegal in most jurisdictions. Best case is when you have clear permission or consent to do some testing. Absent that there's a general consensus that good faith searching for vulnerabilities is ok, as long as you report findings early and squarely. But if you go on to actually abuse the vulnerability to spy on users, look at data etc ... you've crossed a line. For me, cracking a key is much more like that second case. Now you have a secret that can be used for impersonation and decryption. That's not something I'd want to be in possession of without permission.
  - Avamander 2y ago
    They can pursue what they want, it doesn't mean it will go through. Looking at public data, using some other public knowledge to figure out something new does not make it inherently illegal. They didn't crack it on their systems, they didn't subvert it on their systems, they did not use it against their systems. I'd love to see some specific examples under what it could be prosecuted under specifically. Because "that door doesn't actually have a lock" or "the king doesn't actually have clothes" is not practically prosecutable anywhere normal just like that. Especially in the EU, making such cryptographic blunders might even fall foul of NIS2, should it apply to you. In general this also quickly boils down to the topic of "illegal numbers" (https://en.wikipedia.org/wiki/Illegal_number https://en.wikipedia.org/wiki/Illegal_number) as well.
yellow_lead 2y ago
You can say this about a lot of security research, i.e "Showing a bug is exploitable is one thing, but writing a POC is crossing the line!" The problem is that most people won't listen to your security research unless you demonstrate that something is actually possible.
mmastrac 2y ago
Breaking a key isn't criminal. It's just math. Sending emails that would constitute fraud or a violation of another jurisdictional law, relying on that math, is illegal. But again -- it's not the math, it's the action and intent. Pointing out that someone is doing something stupid is also not illegal, though they make try to make your life painful for doing so.
- colmmacc 2y ago
  Secrets themselves are often regarded as sensitive information, and often also categorized in the highest classifications for information protection. This stuff isn't just a game, and in my experience it's not how law enforcement authorities or courts see things. Just as if you made a copy of the physical key for a business's real-world premises, you could well find yourself in trouble. Even if you never "use" it.
cafeinux 2y ago
As mentioned in the article, the key's no longer available and I presume the article has been released only after responsible disclosure was done and with the approval of the key owner (hope so). At this point, it's not more unethical than any other security research performed in the same conditions and with the same outcome.
croemer 2y ago
They only called out 1 out of the ~1.7k domains they found with keys shorter than 1024bits. They _did_ call out the 3 of 10 tested major email providers that don't follow the DKIM RFC properly: Yahoo, Tuta, Mailfence (after having notified them).
- Tutanota 2y ago
  Actually, we did not get notified, but we did see this message - so thanks! We have now fixed the issue and the fix will go live in the next days. Matthias, co-founder of Tuta Mail

tptacek 2y ago

I don't think there's a way to make it criminal, any more than publishing a vulnerability that got you code execution on their servers could be. Actually exploiting it, of course, would be.

colmmacc 2y ago
I think many in cryptography would see cracking a key as a precondition to "actually exploiting it" ... because you've only gotten a cryptographic secret, not "actual data". But I think many others, and many in law enforcement, will see cracking a key as "actually exploiting it". You've exploited the cracking vulnerability to target a particular key, is how they'll see it. Law enforcement also have a natural incentive to want possession of harm-adjacent paraphernalia to carry substantial liability. I think they have a point; that key is private data, and there's a reason people lock keys up in KMSs and HSMs; they can have a large blast radius, and be hard for companies to revoke and rotate. Importantly, a compromise of a key will often trigger notification requirements and so now it is a breach or an incident, in a way that a good faith security vulnerability report is not. To make an extreme example; if you were to crack an important key for a government agency, good luck with that is all I'll say. I sure wouldn't.
- tptacek 2y ago
  The US law most at play in criminal prosecution of computer usage is CFAA, and a clear CFAA predicate is intentional access to a protected computer (18 USC 1030(a)(2)). This distinction is what makes vulnerability research on things like Chrome vulnerabilities generally safe (as long as you don't knowingly spirit exploits to people who are actually attacking people), while vulnerability research on other people's websites (looking for SQLI and SSRF) is risky. The CFAA has a clause about "trafficing in passwords or similar information" (18 USC 1030(a)(6)), but the mental state requirements are very high: that trafficking has to be knowing and with intent to defraud (that intent will be something prosecutors will have to prove at trial). There might be some state law somewhere that makes this risky, but virtually every hacking prosecution in the US anyone has heard of happens under CFAA. I'm not a lawyer, but I've spent a lot of time with CFAA, and I think cracking DKIM keys is pretty safe.
  - colmmacc 2y ago
    By this interpretation it would be perfectly legal to abuse a wifi encryption vulnerability to spy on your neighbors, because that doesn't involve accessing a computer of theirs. My understanding, and IANAL, is that decrypting things that aren't yours is a bad idea and is covered mainly by electronic communications and wire acts, e.g. U.S. Code § 2511 and others.
    - tptacek 2y ago
      A wifi encryption vulnerability that required you to interact with a base station or remote computer would implicate CFAA. A wifi encryption vulnerability that allowed for pure passive interception --- a devastating flaw in 802.11/WPA3 --- might not actually violate any federal law directly. There are probably state laws (I believe Michigan has one) that implicate packet sniffing directly (they were problematic in the early oughts for security researchers). Worth remembering: when CFAA was originally passed, an objection to it was "we already have laws that proscribe hacking computers"; the fraud statutes encompass most of this activity. CFAA's original motivation was literally WarGames: attacks with no financial motivation, just to mess things up. So even without statutory issues, breaking an encryption key and using it to steal stuff (or to gain information and ferry it to others who will use it for crimes) is still illegal. Your guess is as good as mine about whether ECPA covers wifi sniffing. But: presuming you obtain an encryption key through lawful means, ECPA can't (by any obvious reading) make cracking that key unlawful; it's what you'd do with the key afterwards that would be problematic.
      - colmmacc 2y ago
        My understanding of the ECPA and other acts is that you can't intercept, decode, or receive by other intentional means any information or communications that aren't "generally accessible" without permission. It's pretty broad and doesn't care about the "how". Private keys are not "generally accessible" and my concern is that the authorities will see cracking the key itself as issue enough, and unlawful. If a security researcher triggers painful breach notifications, which could well happen for a compromised private key, I don't think it's unthinkable at all that an upset target will find a DA who is happy to take this interpretation. I don't think this specific DKIM case is particularly high-risk, but I still wouldn't do it without permission from the key holder.

michaelmior 2y ago

I am also not a lawyer, but I would suspect it's not criminal to crack a real-world in-use key if you do so using only publicly available information and you don't actually do anything with the result.

colmmacc 2y ago
Let's say you local coffee shop is featured in a local news piece and the blithe owner happened to get photographed holding the store key. That's now easy to clone from public information. Would you be comfortable actually doing it? Reporting the issue is fine - "Hey you should rekey your locks!". Actually making a clone of the key, and then showing "hey it fits" will get you more traction more quickly ... but there's also plenty of Police Departments who might well arrest you for that.
- michaelmior 2y ago
  > showing "hey it fits" That's exactly what I meant in terms of not actually doing anything with the result. That said, it's obviously somewhat different with a physical key than a cryptographic key.

phoe-krk 2y ago

> for me, actually cracking a real-world in-use key crosses an ethical line that makes me uncomfortable They've contacted the company with the vulnerability and resolved it before publishing the article - search the original article for the substring "now no longer available". Usually, you demonstrate that an online system is vulnerable by exploiting that vulnerability in good faith, documenting the research, and submitting it for review. It does not matter if you're cracking an encryption scheme, achieving custom code execution for a locked-down game console, proving that you can tamper with data in a voting machine, or proving that you can edit people's comments on a Google Meet Q&A session - the process is the same. If you say something's vulnerable, people can shrug it off. If you say and prove something's vulnerable, the ability to shrug it off shrinks. If you say and prove something's vulnerable and that you'll publish the vulnerability - again, using the industry standard of disclosure deadlines and making the vulnerability public after 60-or-so days of attempting to contact the author - the ability to shrug it off effectively disappears.

colmmacc 2y ago
I read the article, and I don't think it changes it. If you crack someone's key, they might be well within their rights to pursue a criminal prosecution. Of course it would also have a Streisand effect and there's reasons not to, but I personally wouldn't allow or recommend a security researcher to do it. It's needlessly risky. In general, subverting security and privacy controls tends to be illegal in most jurisdictions. Best case is when you have clear permission or consent to do some testing. Absent that there's a general consensus that good faith searching for vulnerabilities is ok, as long as you report findings early and squarely. But if you go on to actually abuse the vulnerability to spy on users, look at data etc ... you've crossed a line. For me, cracking a key is much more like that second case. Now you have a secret that can be used for impersonation and decryption. That's not something I'd want to be in possession of without permission.
- Avamander 2y ago
  They can pursue what they want, it doesn't mean it will go through. Looking at public data, using some other public knowledge to figure out something new does not make it inherently illegal. They didn't crack it on their systems, they didn't subvert it on their systems, they did not use it against their systems. I'd love to see some specific examples under what it could be prosecuted under specifically. Because "that door doesn't actually have a lock" or "the king doesn't actually have clothes" is not practically prosecutable anywhere normal just like that. Especially in the EU, making such cryptographic blunders might even fall foul of NIS2, should it apply to you. In general this also quickly boils down to the topic of "illegal numbers" (https://en.wikipedia.org/wiki/Illegal_number https://en.wikipedia.org/wiki/Illegal_number) as well.

yellow_lead 2y ago

You can say this about a lot of security research, i.e "Showing a bug is exploitable is one thing, but writing a POC is crossing the line!" The problem is that most people won't listen to your security research unless you demonstrate that something is actually possible.

mmastrac 2y ago

Breaking a key isn't criminal. It's just math. Sending emails that would constitute fraud or a violation of another jurisdictional law, relying on that math, is illegal. But again -- it's not the math, it's the action and intent. Pointing out that someone is doing something stupid is also not illegal, though they make try to make your life painful for doing so.

colmmacc 2y ago
Secrets themselves are often regarded as sensitive information, and often also categorized in the highest classifications for information protection. This stuff isn't just a game, and in my experience it's not how law enforcement authorities or courts see things. Just as if you made a copy of the physical key for a business's real-world premises, you could well find yourself in trouble. Even if you never "use" it.

cafeinux 2y ago

As mentioned in the article, the key's no longer available and I presume the article has been released only after responsible disclosure was done and with the approval of the key owner (hope so). At this point, it's not more unethical than any other security research performed in the same conditions and with the same outcome.

croemer 2y ago

They only called out 1 out of the ~1.7k domains they found with keys shorter than 1024bits. They _did_ call out the 3 of 10 tested major email providers that don't follow the DKIM RFC properly: Yahoo, Tuta, Mailfence (after having notified them).

Tutanota 2y ago
Actually, we did not get notified, but we did see this message - so thanks! We have now fixed the issue and the fix will go live in the next days. Matthias, co-founder of Tuta Mail