Ik Rae Jeong , Dong Hoon Lee

The KIPS Transactions:PartC, Vol. 12, No. 7, pp. 949-958, Dec. 2005
10.3745/KIPSTC.2005.12.7.949,   PDF Download:

Abstract

In the paper we study key agreement schemes when a party needs to establish a session key with each of several parties, thus having multiple session keys. This situation can be represented by a graph, called a key graph, where a vertex represents a party and an edge represents a relation between two parties sharing a session key. The purpose of the paper is to design a key agreement protocol forkey graphs to establish all session keys corresponding to al;l edges in a key graph simultaneously in a single session. A key agreement protocol of a key graph is a natural extension of a two-party key agreement protocol. We propose a new key exchange model for key graph which is an extension of a two-party key exchange model. Using the so-called randomness re-use technique thisch re-uses random values to make session keys for different sessions, we suggest two efficient key agreement protocols for key graphs based on the decisional Diffie-Hellman assumption, and prove their securitues in the key exchange model of key graphs. Our first cheme requires only a single round and provides key independence. Our second scheme requires two rounds and provides forward secerecy. Both are proven secure in the standard mode. The suggested protocols are the first pairwise key agreement protocols and more efficient than a simple scheme which use a two-party keyexchange for each necessary key. Suppose that a user makes a session keywith n other users, respectively. The simple scheme''s computational cost and the length ofthe transmitted messages are increased by a factor of n. The suggested protocols''s computational cost also depends on n, nut the length of the transmitted messages are constant.,

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