All else equal, in practical terms you should probably devote all your time to first finding the person(s) that already know the private keys, and then patiently persuading them to share. I believe the technical term for this is “rubber hose cryptanalysis”.
Yes. At the beginning, it is better to work on A than to work on B, because the machine choosing A is more likely. After the beginning, it is still better to work on A than to work on B, because finishing A will be easier than finishing B if you’ve already worked on it some. On the off chance that you don’t complete both decryptions, it’s better to have the one you’re more likely to need.
I think some of us know considerably less about cryptography than you do. I think sketerpot’s suggestion was based on the assumption that most of the work would just be done by the computer and that the hacker could just sit back and relax while his two laptops went to work on the encryptions (you know, like in movies!). If the hacker needs to spend a month of his/her time (rather than computer time) to complete the decryption, then I see what you’re talking about.
The assumption that most of the work would be done by the computer is correct. Perhaps sketerpot was assuming that breaking a decryption key is an operation that’s impossible to parallelize (i.e. two computers both working on a single key would be no better than just one computer doing so), whereas I’m pretty sure that two computers would do the job twice as fast as one computer.
Why would you do that? If one key is more likely than the other, you should devote all your time toward breaking that key.
All else equal, in practical terms you should probably devote all your time to first finding the person(s) that already know the private keys, and then patiently persuading them to share. I believe the technical term for this is “rubber hose cryptanalysis”.
Even if there is a high probability of completing both decryptions and the probability the machine chooses A over B is only slightly over .5?
Yes. At the beginning, it is better to work on A than to work on B, because the machine choosing A is more likely. After the beginning, it is still better to work on A than to work on B, because finishing A will be easier than finishing B if you’ve already worked on it some. On the off chance that you don’t complete both decryptions, it’s better to have the one you’re more likely to need.
I think some of us know considerably less about cryptography than you do. I think sketerpot’s suggestion was based on the assumption that most of the work would just be done by the computer and that the hacker could just sit back and relax while his two laptops went to work on the encryptions (you know, like in movies!). If the hacker needs to spend a month of his/her time (rather than computer time) to complete the decryption, then I see what you’re talking about.
The assumption that most of the work would be done by the computer is correct. Perhaps sketerpot was assuming that breaking a decryption key is an operation that’s impossible to parallelize (i.e. two computers both working on a single key would be no better than just one computer doing so), whereas I’m pretty sure that two computers would do the job twice as fast as one computer.
Ah, yes. That makes sense. Thanks for your patience.