re once they get your keys in article dockmaster ncsc mil grant dockmaster ncsc mil lynn r grant writes about people so far have asked once the fbi gets your clipper keys won t they be able to read all your future and past traffic there has been no response from nist nsa ms denning mr hellman or anyone else who might be able to give us an authoritative answer this is troubling didn t nsa think about this or is it a feature and they thought we wouldn t notice i would have thought that by now they would have responded with something of the form well that won t be a problem because don alvarez posted a good partial solution to this problem to comp risks i ll present my variant on it instead since i feel it s a bit stronger against some likely attempts to cheat depends on the protocol that s followed for reading traffic briefly the cops get a wiretap warrant and record the call they then notice the encryption and the disclosure header it along with a copy of their warrant is sent to the fbi or whoever it is who holds the family key the f holder decrypts the header and sends the serial number n and the encrypted session key u k to the escrow agents they in turn use u and u to recover k and send that to the local police note how this solves the problem of wiretapping forever neither the cops nor the fbi ever see u so they can t read other traffic every request must be validated by both the fbi and the escrow agents the cops and the fbi together can t cheat since they don t have u i regard that as a likely pairing of folks who might try to beat the system it s to prevent this that i modified alvarez s scheme the escrow agents can t read the conversation since they don t have it all they have is n and u k and the police don t even see n it s harder to see how to block decryption of old warrantless wiretaps there is one protection you have to persuade the escrow agents that the call is current but that s not nearly as strong there are approaches i can see that might work involving sequences of data on an unalterable medium complete with cryptographic protection against insertion onto a new medium but i don t have anything yet that isn t too complex for comfort or too hard to install in the real world the nsa might have an answer they may or may not be smarter than me but i ve been working on this for a week and they ve had years
