E. Okamoto

Bio: E. Okamoto is an academic researcher from NEC. The author has contributed to research in topics: Key distribution & Authentication. The author has an hindex of 2, co-authored 2 publications receiving 204 citations.

Key distribution system based on identification information

Abstract: A key distribution system (KDS) based on identification information (ID-based KDS) is presented. The system is founded on the Diffie-Hellman public key distribution scheme and has an identity authentication function. It uses an individual user's identification information instead of the public file used in the Diffie-Hellman scheme. It does not require any services of a center to distribute work keys or users to keep directories of key-encrypting keys. Therefore, key management in cryptosystems can be simplified by adopting the ID-based KDS. Two kinds of identity-based key distribution system are proposed and applied to actual communication networks. One uses two-way (interactive) communication to distribute work keys, while the other uses one-way communication. Modular exponentiations of large numbers, used in the systems, are implemented with digital signal processors. >

Identity-based information security management system for personal computer networks

Abstract: A network information security management system which authenticates and/or encrypts messages is proposed. Both authentication and key distribution are executed in a simple scheme. Once the system is set up, the transactions are done independently by the users involved, yet the amount of information that users must keep is small. The experimental implementation of the system on a personal computer network, using IC cards (smart cards) and digital signal processors, is described. The signal processors shorten calculation time and make the concept practical. >

Handbook of Applied Cryptography

Abstract: From the Publisher: A valuable reference for the novice as well as for the expert who needs a wider scope of coverage within the area of cryptography, this book provides easy and rapid access of information and includes more than 200 algorithms and protocols; more than 200 tables and figures; more than 1,000 numbered definitions, facts, examples, notes, and remarks; and over 1,250 significant references, including brief comments on each paper.

Authentication and authenticated key exchanges

Abstract: We discuss two-party mutual authentication protocols providing authenticated key exchange, focusing on those using asymmetric techniques. A simple, efficient protocol referred to as the station-to-station (STS) protocol is introduced, examined in detail, and considered in relation to existing protocols. The definition of a secure protocol is considered, and desirable characteristics of secure protocols are discussed.

Perfectly-Secure Key Distribution for Dynamic Conferences

Abstract: A key distribution scheme for dynamic conferences is a method by which initially an (off-line) trusted server distributes private individual pieces of information to a set of users. Later any group of users of a given size (a dynamic conference) is able to compute a common secure key. In this paper we study the theory and applications of such perfectly secure systems. In this setting, any group of t users can compute a common key by each user computing using only his private piece of information and the identities of the other t - 1 group users. Keys are secure against coalitions of up to k users, that is, even if k users pool together their pieces they cannot compute anything about a key of any t-size conference comprised of other users.First we consider a non-interactive model where users compute the common key without any interaction. We prove a lower hound on the size of the user's piece of information of (k+t-1 t-1) times the size of the common key. We then establish the optimality of this bound, by describing and analyzing a scheme which exactly meets this limitation (the construction extends the one in [2]). Then, we consider the model where interaction is allowed in the common key computation phase, and show a gap between the models by exhibiting an interactive scheme in which the user's information is only k + t - 1 times the size of the common key. We further show various applications and useful modifications of our basic scheme. Finally, we present its adaptation to network topologies with neighborhood constraints.

A secure and efficient conference key distribution system

Abstract: We present practical conference key distribution systems based on public keys, which authenticate the users and which are ‘proven’ secure provided the Diffie-Hellman problem is intractable. A certain number of interactions is needed but the overall cost is low. There is a complexity tradeoff. Depending on the network used, we either have a constant (in the number of conference participants) number of rounds (exchanges) or a constant communication and computation overhead. Our technique for authentication can be extended and used as the basis for an authentication scheme which is ‘proven’ secure against any type of attack, provided the Discrete Logarithm problem is intractable.

Protocols for Authentication and Key Establishment

Abstract: Protocols for authentication and key establishment are the foundation for security of communications. The range and diversity of these protocols is immense, while the properties and vulnerabilities of different protocols can vary greatly.This is the first comprehensive and integrated treatment of these protocols. It allows researchers and practitioners to quickly access a protocol for their needs and become aware of existing protocols which have been broken in the literature.As well as a clear and uniform presentation of the protocols this book includes a description of all the main attack types and classifies most protocols in terms of their properties and resource requirements. It also includes tutorial material suitable for graduate students.