I don't get the problem. It's a server based game right? So just use some hybrid encryption? I don't get why you'd want to play with a commutative system system, you probably could do it with AES in OFB (Streamcipher, thus using XOR) mode, but I don't get the advantage. What are you trying to hide from the participants? Can't you simply stop sending that data to them? You want both to have the data, but make them only able to read it if both agree? Just encrypt it twice using AES OFB and give each one a key. In order to get the plaintext they have to apply both keys (thus exchange keys), though the order in which they're applied doesn't matter. That's what you want to archive using a commutative system?
Elias Cameron Hutchison wrote: > [I sent this directly to Elias by accident - gmail newbie here. Here > it is again for the list] > > I don't think man-in-the-middle is going to be a problem. My goal > here is to make sure information is not revealed to the participants > (of which there are two, but the protocol could probably be extended > to more easily enough) before both players agree to it. > > Anyway, if the man-in-the-middle does become an issue, the game can be > played over a SSL/TLS link so I dont have to invent a new identity > scheme for the game (i.e. make it possible to set up comms with > existing certs - I hate the proliferation of different incompatible > certs for different systems that I'm not going to add to it). > > None of that matters though, unless I find an appropriate cipher for > the game itself. :-) > > Cheers > > On Sun, Jul 4, 2010 at 9:32 AM, Elias <[email protected] > <mailto:[email protected]>> wrote: > > Don't forget about man-in-the-middle - You'd have to use signatures at > least! So better use asymmetric crypto in the first place ;) > > On Jul 1, 6:48 am, Cameron Hutchison <[email protected] > <mailto:[email protected]>> wrote: > > Hi crypto++ users, > > > > I'm looking for a commutative cipher to use to implement a card game > > protocol (any type of card game, not just the 52/54 standard deck > > games). > > > > My research has led me to the Massey-Omura cryptosystem, but I > cannot > > find any implementations of it. I have read of references to > elliptic > > curve variations on M-O but most of what I read goes over my head. I > > don't have the math background to understand the actual > implementation > > and theory behind these cryptosystems. So I'm not sure if what I've > > read is saying that ECC is commutative or not, but my > experiments with > > the ECC systems in crypto++ leads me to believe it is not. > > > > Are there any commutative ciphers in crypto++ (besides XOR)? > Symmetric > > key would be simplest, but I can also work with asymmetric key > > algorithms. > > > > Thanks > > -- > You received this message because you are subscribed to the > "Crypto++ Users" Google Group. > To unsubscribe, send an email to > [email protected] > <mailto:[email protected]>. > More information about Crypto++ and this group is available at > http://www.cryptopp.com. > > > -- > You received this message because you are subscribed to the "Crypto++ > Users" Google Group. > To unsubscribe, send an email to > [email protected]. > More information about Crypto++ and this group is available at > http://www.cryptopp.com. -- You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to [email protected]. More information about Crypto++ and this group is available at http://www.cryptopp.com.
