On Sun, 10 Sep 1995, Adam Shostack wrote:
Good question, but a quick modification allows for effective bootstrapping. If I want to start consulting for Amalgameted Consolodated, I can offer them a 10 free questions deal to bootstrap things with. Mallet can only cheat if my offer was broadcast. (I presume that Amalagated' keys are somehow strongly verified, and the negotiantions are kept secret from Eve and Mallet.)
This scheme doesn't quite work. (Let's call Amalgameted Bob, to keep names short.) Bob can create a new, unlinkable pseudonym and give the same offer to Carol under the new pseudonym. Then, Bob acts as Mallet and passes messages back and forth between Alice and Carol. At the end of the 10 free questions, Bob terminates its contract with Alice, leaving Alice with nothing and Bob's pseudonym a certain amount of reputation with Carol.
There might also be fingerprinting technologies that allow me to embed a signature in the documents returned to clients that would allow me to show that Mallet stole them. (Which might, incidentally, get Mallet a job in some circles...If thats known, Bob and Alice can collude to make it appear that Bob was Mallet, and thus forge a reputation.
Fingerprinting may be useful in some situations, but is clearly not a perfect solution to this problem. Alice may be able to prove to Mallet's customers that she originally wrote the answers, but if their communications with Mallet are private, how does Alice even know who those customers are? Also, I'm not too familiar with fingerprinting technologies, but Mallet may be able to remove the identifying marks by translating the answers to a different form while preserving the meaning. Wei Dai