If a researcher manages to make a cryptanalytic breakthrough on a cryptographic algorithm or protocol that is in use, what should they do?

Has this ever happened before? What are the implications for release and how do those relying on such systems ensure they are not caught in a situation where the crypto-system on which they depend is trivially broken?


  • What details would you make available online?
  • Who would you release full details to?
  • How are affected parties notified?
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    $\begingroup$ I'm not sure this is the right site for this question. This is not about cryptography, more about ethics, I suppose. $\endgroup$ – Paŭlo Ebermann Aug 26 '11 at 10:44
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    $\begingroup$ @Paŭlo I agree that the field of cryptography needs to be able to discuss attacking and defending in a completely abstract way, using the terminology such that it's unloaded from the ethics of any particular human situation. More often than not, it's the real-world defender who benefits from the 'attack' research anyway. Nevertheless, it's probably not a good idea for any researcher to be completely oblivious to the real-world implications of their research. It think it's an important (even if maybe a little far-fetched) question that needs to be asked. If not here, then where? $\endgroup$ – Marsh Ray Aug 26 '11 at 14:18
  • $\begingroup$ I once faced a similar situation, for a much lesser target. Here is what I did $\endgroup$ – fgrieu Aug 26 '11 at 15:31
  • $\begingroup$ I've edited the question to make it more generic; let me know what you think (I can always roll it back, or the OP can). I think, personally, that it is a difficult case to decide if this question is in-scope, so I'll be guided by everyone else. Also, I've introduced an ethics tag which may or may not be a good idea - anyone with any better suggestions (soft-question?) please shout. $\endgroup$ – user46 Aug 26 '11 at 15:51
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    $\begingroup$ First of all, you should never assume that you're the only party that knows about it. $\endgroup$ – Marsh Ray Aug 28 '11 at 12:35

Well, first off, the question doesn't arise that often in practice. People do find cryptographical weaknesses; however, generally they are purely of theoretical interest, or if they could be used in a real attack, it may take quite a while before someone figures out how to use it. As an example of the second case, Ms. Wang announced an efficient way to create MD5 collisions; this is a severe break of the MD5 security properties, but it took people quite a while to figure out how to translate that into being able to obtain a bogus certificate (by asking for an innocuous one from a CA).

On the other hand, it does happen on occasion; one example that springs to mind is WEP and the key recovery attack.

Now, in my opinion, the ethical thing to try to do is to get people to stop using the broken protocol, and switch to something which doesn't have known weaknesses. However, in practice, that appears to be difficult. Once they have a system in place, quite a lot of people are loathe to update it. In addition, when cryptographical hardware is involved, sometimes the fix involves hardware modification, and so updating things would involve real money (rather than just a software update). One example of someone ignoring an announced attack would be the TJX credit card breach; this attack was done using the WEP key recovery attack that was announced 5+ years earlier.

So, what should we do? Well, I don't see any good options. Not publishing the result doesn't appear to work (we leave the weaknesses in place for the blackhats to find and exploit). Publishing the result does mean that some will update, but others won't bother. Publishing the fact that we have a result will generally mean that you won't be taken seriously (unless you're already a cryptographical Big Name), and the blackhats will be alerted that there is a weakness.

My personal feeling is that publishing the result is the "least worse".

[Hmmmm, we're supposed to avoid statements based on opinions; for a question about ethics like this, I don't see how I can avoid it]

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    $\begingroup$ I think there's enough history and data at this point that we can say full disclosure is a good principle and default course of action. Generally the only parties opposed to it are those who actually want (perversely) the vulnerable state to persist longer. $\endgroup$ – Marsh Ray Aug 28 '11 at 12:31
  • $\begingroup$ Depending on when you consider something a breakthrough I believe this happens much more often than one thinks. Consider the integer overflow on BitCoin: the idea behind the currency is decentralization through open source code of a certain peer to peer protocol. He found a flaw in its implementation. Instead of trying to contact a "certain" centralized person, he showed to everyone listening to the blockchain what the problem was and anyone with debugger skills could find the problem. Also consider that windows virus that closed the vulnerability it used. $\endgroup$ – propaganda Jan 22 '12 at 18:48

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