KEY PRE-DISTRIBUTION SYSTEM (KPS Clause Samples

KEY PRE-DISTRIBUTION SYSTEM (KPS. Key pre-distribution system (KPS) (a.k. a. non- interactive conference distribution system) can be regarded as a non-interactive group key agreement. In this case, the shared key of a given group is fixed after the setup. If a group is updated, then the group key changes to the shared key of the new group. The drawback of KPS is that the user key size is combinatorial large in the total number of users (if the system is unconditionally secure). Another drawback is that the group key of a given group cannot be changed even if it is leaked unexpectedly (e.g., cryptanalysis of cipher texts bearing this key). The key size problem may be overcome if a computationally secure system is used, while the key leakage problem is not easy. Further, computationally secure KPS is only known for the two-party case and the three-party case. KPS with a group size greater than 3 is still open.