Review the solutions proposed in the discussion of the Wireless Equivalent Privacy protocol design, outlining ways in which each solution could be implemented and discussing any unresolved issues or drawbacks.

a) Sharing a single key: Solution, use a public-key based protocol for negotiating individual keys.

b) Base stations are never authenticated: Solution, base stations should supply a certificate.

c) Inappropriate use of a stream cipher: Solution: Negotiate a new key after a time less than the worst case for repetition. An explicit termination code would be needed, as is the case in TLS.

d) The RC4 stream cipher weakness Solution: Provision for the negotiation of cipher specifications

e) Users often didn’t deploy the protection Solution: Better default settings and documentation.

a) How would authorized users establish their credentials? They would need a certificate signed by an authority such as the administrator of the network. As a simple (primitive) solution could get the certificate using a physical channel (e.g. on a memory stick from the sys admin). But a more sophisticated scheme would have the sys admin establish a database contianing a set of certificates for authorized users. The users would establish their identities using public key certificates in order to utilize their authorization. Once the authorization has occured, the protocol to establish a shared encryption key would proceed in a manner similar to (or even using) SSL/TSL.

b) The certificate could be supplied as part of the exchange that is described above. Care is needed to ensure that the public key in the base-station certificate is used to establish the shared key.

c) The worst case for repetition is in the order of hours. A base station should initiate the negotiation of new keys without disruption of communication using a protocol similar to the TLS change cipher spec mechanism. Drawbacks: the TLS mechanism must be implemented everywhere. It may not be possible to perform a cipher change without interruping a real-time datastream.

d) the main problem is the inflexibility of hardwiring the cipher spec into the protocol definition. Solution is to allow communication partners to negotiate a cipher algorithm as in TLS. This requires a handshake protocol, similar to the change cipher spec mechanism required in the previous answer.

e) The issue here is the importance given to security by administrators and users. It’s worth noting that the failure to do so has resulted in several recorded incidents of loss of privacy and some decisions to suspend the use of WiFi networks.