XTR is one of the most efficient public-key cryptosystems that allow us to compress the communication bandwidth of their ciphertext. The compact representation can be achieved by deploying a subgroup Fq2 of extension field Fq6, so that the compression ratio of XTR cryptosystem is 1/3. On the other hand, Dijk et al. proposed an efficient public-key cryptosystem using a torus over Fq30 whose compression ratio is 4/15. It is an open problem to construct an efficient public-key cryptosystem whose compression ratio is smaller than 4/15. In this paper we propose a new variant of XTR cryptosystem over finite fields with characteristic three whose compression ratio is 1/6. The key observation is that there exists a trace map from Fq6 to Fq in the case of characteristic three. Moreover, the cost of compression and decompression algorithm requires only about 1% overhead compared with the original XTR cryptosystem. Therefore, the proposed variant of XTR cryptosystem is one of the fastest public-key cryptosystems with the smallest compression ratio.

The delay characteristics of the MPsLS, a data forwarding scheme used for a core area of the integrated data service network, are discussed and analyzed. MPsLS has the capability of guaranteeing QoS on the per-flow level for time-sensitive applications and simultaneously maintaining the high utilization of network resources. In the MPsLS core area, the forwarding process is implemented with a fine-grain slot synchronization model, and at the ingress edge nodes, the forwarding process is carried with a coarse-grain frame synchronization model. The delay analyses are done according to three service models: the exact synchronization model, the less strict synchronization model for the appointed channels, and an asynchronous model for the filler channels. The authors give estimation equations of mean delay between edge-to-edge nodes in an MPsLS network, and introduce an effective method to determine the reserved bandwidth for given application flows based on numerical calculations from those theory analysis and simple simulation results.

A new practical parallel garbage collection algorithm and its correctness proof are presented. Some results of its implementation applied to a small size LISP system are reported. The algorithm, which is constructed on the condition that all active lists are bound in the linear stack, needs only one mark bit for each node and a scan-request-flag (SREQ) for the system. The minimum utilization of critical sections, where the operations on SREQ are performed, dispenses with the need for multicolored marking, such as white, gray or black. Also marking efficiency improves since it enables applying a recursive trace-and-mark method instead of a simple scan-and-markmethod. An outline of the correctness proof is as follows : It is proned by induction that the relation, wherein the active-node-set is a subset of the mark-reachable-set, which is defined as the set of all the nodes to which some links exist from any nodes already marked, is retained during the mark propagating phase for any list processing primitives, so that the algorithm guarantees that no active nodes are reclaimed. Last, the implementation of a small size LISP system with this algorithm is reported. The comparison between the parallel system and the regular one is discussed on the basis of actual data.