Re: [viff-devel] Securely running the same VIFF program multiple times
Thomas P Jakobsen writes: > On Thu, Aug 12, 2010 at 12:06, Martin Geisler wrote: > >> Would it not be fairly easy to let each of the players secret share a >> random integer, add all the shared numbers, open the result, and use >> that as the computation ID? That is, automate this so that you don't >> have to agree on a certain computation ID in advance. > > That might well be a better solution. But there's a trade-off; it > makes it easier to use, but slows down the execution time. Of course, > for most applications a single secret sharing and an opening is > affordable. Yes, I don't think performance is an issue here. > Another potential issue is that some runtimes may require prss in > order to share and/or open values. That would give us kind of a > chicken-egg problem. I meant that they should just Shamir share the random number. Malicious parties may then of course produce an inconsistent sharing and this will result in the parties using different seeds for PRSS. I think that would be no worse than if the parties had used different command line options. -- Martin Geisler aragost Trifork Professional Mercurial support http://aragost.com/mercurial/ ___ viff-devel mailing list (http://viff.dk/) viff-devel@viff.dk http://lists.viff.dk/listinfo.cgi/viff-devel-viff.dk
Re: [viff-devel] Securely running the same VIFF program multiple times
On Thu, Aug 12, 2010 at 12:06, Martin Geisler wrote: > Would it not be fairly easy to let each of the players secret share a > random integer, add all the shared numbers, open the result, and use > that as the computation ID? That is, automate this so that you don't > have to agree on a certain computation ID in advance. That might well be a better solution. But there's a trade-off; it makes it easier to use, but slows down the execution time. Of course, for most applications a single secret sharing and an opening is affordable. Another potential issue is that some runtimes may require prss in order to share and/or open values. That would give us kind of a chicken-egg problem. Anyway, the best solution may be to let it up to each runtime to decide what to do on startup and which parameters to use. Regards, Thomas ___ viff-devel mailing list (http://viff.dk/) viff-devel@viff.dk http://lists.viff.dk/listinfo.cgi/viff-devel-viff.dk
Re: [viff-devel] Securely running the same VIFF program multiple times
Thomas P Jakobsen writes: > Hi all, > > As you may or may not know, running the same VIFF program more than > once using the same set of player configuration files is insecure when > the runtime relies on pseudo-random secret sharing. This is the case > for e.g. the PassiveRuntime. > > This is not a bug, but rather a consequence of the way in which we use > pseudo-random secret sharing. In order to maintain security, a new set > of player configuration files has to be generated for each run. > > In some practical settings this turns out to be inconvenient. So we > recently added a changeset (1538:9d4f9551644c) that fixes this. It > means that one no longer has to use fresh configuration files for each > run. Instead, there's now a command line option called computation-id, > e.g. > > python my_viff_program.py --computation-id=42 player-1.ini > > When using runtimes based on pseudo-random secret sharing, like > PassiveRuntime, one can then safely reuse the configuration files as > long as the computation ids are unique. That is, for each run with a > given set of configuration files, the players should agree on a > computation id that has not been used before for that set of > configuration files. Would it not be fairly easy to let each of the players secret share a random integer, add all the shared numbers, open the result, and use that as the computation ID? That is, automate this so that you don't have to agree on a certain computation ID in advance. -- Martin Geisler aragost Trifork Professional Mercurial support http://aragost.com/mercurial/ ___ viff-devel mailing list (http://viff.dk/) viff-devel@viff.dk http://lists.viff.dk/listinfo.cgi/viff-devel-viff.dk
[viff-devel] Securely running the same VIFF program multiple times
Hi all, As you may or may not know, running the same VIFF program more than once using the same set of player configuration files is insecure when the runtime relies on pseudo-random secret sharing. This is the case for e.g. the PassiveRuntime. This is not a bug, but rather a consequence of the way in which we use pseudo-random secret sharing. In order to maintain security, a new set of player configuration files has to be generated for each run. In some practical settings this turns out to be inconvenient. So we recently added a changeset (1538:9d4f9551644c) that fixes this. It means that one no longer has to use fresh configuration files for each run. Instead, there's now a command line option called computation-id, e.g. python my_viff_program.py --computation-id=42 player-1.ini When using runtimes based on pseudo-random secret sharing, like PassiveRuntime, one can then safely reuse the configuration files as long as the computation ids are unique. That is, for each run with a given set of configuration files, the players should agree on a computation id that has not been used before for that set of configuration files. A consequence of this is that the length of all program counters are increased by one. This means that the data that needs to be sent across the network increases a bit, but we expect it to have only negligible impact on performance. Regards, Thomas ___ viff-devel mailing list (http://viff.dk/) viff-devel@viff.dk http://lists.viff.dk/listinfo.cgi/viff-devel-viff.dk
