[e-lang] Card game based on covert channels

[Constantine Plotnikov]

Chris Hibbert wrote:

>> I have just remembered that there is a card game that is based on
>> covert channels. Tt is "Contract Bridge". Covert channel is
>> established and used in bidding process. There is also a way to
>> introduce a noise in the channel to confuse opponents covert channel.
>>
>> This game might be a good sample to explain what is a covert channel
>> in the protocol in security books or articles.
>
>
> That's an interesting idea, but the fact that the bidders are required 
> to explain their (partners') bids makes it more overt than covert.  I 
> think it may make a good opening example, but if you try to explain it 
> in any depth, the analogy will get pretty strained.

This is a covert channel because the formal surface meaning of the 
protocol is making bids. But partners interpreting it as information 
about state of their hands. I have not played game myself, so it is 
interesting to learn that there are even rules for using bids as covert 
channel ;).

>
> And most bidding systems discourage injecting noise into the 
> opponents' channel, since your partner is expected to decode that as a 
> signal to her.
>
I had a friend that played the game quite much and he told me that some 
bid values are often reserved in the protocol to make empty shots that 
answers using standard systems more difficult if usage of standard 
system is detected. He also did not use standard systems for some reasons.

Constantine