Check out http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing Encrypt the answer and maybe some salt or

Check out http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing Encrypt the answer and maybe some salt or if you're really brave, some known plaintext provided by the other guy (here be dragons), give the pub key for every node to everyone, split the private key using SSSS or some other strategy, and give all SSSS key-halve to the other guy and google only gives up precisely two of their halves upon request so you only get to SSSS reassemble the private keys for two nodes and thus only know two nodes. There are some other schemes involving hashing that I feel a little fuzzier about. Also look into "double spend" algos for digital cash. Go ahead, opfor, make my day, you double spend a token and you get more data but GOOG gets the transaction's swiss bank account number so the financial transaction auto-completes. That might take a little more fooling around at the protocol level to set up.