What I want to do is to look at the packets inbound for my PC, to see if they contain information of other clients that should not be sent. The packets are encrypted with SSL, but since they are being sent to my PC the informaion to decrypt them must be on my PC.
Sorry brm I missed that first time. Its's the no doubt.

Hoss has the best solution for you. Just sniff what you are receiving and check the (plain) headers to see if they belong to you. If you are getting other people's stuff then they are probably getting yours as you have suggested.

They key won't be on your computer, it will be on theirs, so your key is actually irrelevant. The issue is can the packets be cracked? the answer to which has to be "yes" but with what effort?

I think that I have addressed several of the other issues?

Basically, if they are sending stuff to you that you should not be getting, then they need to sort their system out, if only because it is a gross waste of bandwidth?