Mathematics / Matematik

Permanent URI for this collectionhttps://hdl.handle.net/11147/8

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Institution Author: search.filters.institutionAuthor.Fujioka, Atsushi

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  • Article
    Utilizing Postponed Ephemeral and Pseudo-Static Keys in Tripartite and Identity-Based Key Agreement Protocols
    (International Association for Cryptologic Research, 2009) Fujioka, Atsushi; Suzuki, Koutarou; Ustaoğlu, Berkant
    We propose an new one-round implicitly authenticated three-party protocol that extends Joux's protocol as well as a two-party identity-based protocol. Our protocols have a single communication round that consists of ephemeral (one-time) public keys along with certificates in the tripartite protocol, and identities in the identity-based setting. As such our protocols are communication efficient and furthermore do not require enhanced message format.
  • Conference Object
    Citation - WoS: 28
    Strongly Secure Authenticated Key Exchange Without Naxos' Approach
    (Springer Verlag, 2009) Kim, Minkyu; Fujioka, Atsushi; Ustaoğlu, Berkant
    LaMacchia, Lauter and Mityagin [15] proposed the extended Canetti-Krawczyk (eCK) model and an AKE protocol, called NAXOS. Unlike previous security models, the adversary in the eCK model is allowed to obtain ephemeral secret information related to the test session, which makes the security proof difficult. To overcome this NAXOS combines an ephemeral private key x with a static private key a to generate an ephemeral public key X; more precisely X∈=∈g H(x,a). As a result, no one is able to query the discrete logarithm of X without knowing both the ephemeral and static private keys. In other words, the discrete logarithm of an ephemeral public key, which is typically the ephemeral secret, is hidden via an additional random oracle. In this paper, we show that it is possible to construct eCK-secure protocol without the NAXOS' approach by proposing two eCK-secure protocols. One is secure under the GDH assumption and the other under the CDH assumption; their efficiency and security assurances are comparable to the well-known HMQV [12] protocol. Furthermore, they are at least as secure as protocols that use the NAXOS' approach but unlike them and HMQV, the use of the random oracle is minimized and restricted to the key derivation function. © 2009 Springer-Verlag Berlin Heidelberg.