Paper 2012/460

Information-Theoretic Timed-Release Security: Key-Agreement, Encryption, and Authentication Codes

Yohei Watanabe and Takenobu Seito and Junji Shikata

Abstract

In this paper, we study timed-release cryptography with information-theoretic security. As fundamental cryptographic primitives with information-theoretic security, we can consider key-agreement, encryption, and authentication codes. Therefore, in this paper we deal with information-theoretic timed-release security for all those primitives. Specifically, we propose models and formalizations of security for information-theoretic timed-release key-agreement, encryption, and authentication codes; we also derive tight lower bounds on entities' memory-sizes required for all those ones; and we show optimal constructions of all those ones. Furthermore, we investigate a relationship of mechanisms between information-theoretic timed-release key-agreement and information-theoretic key-insulated key-agreement. It turns out that there exists a simple algorithm which converts the former into the latter, and vice versa. In the sense, we conclude that these two mechanisms are essentially close.

Note: We derived tight lower bounds on entities' memory-sizes required for TRA-codes. We also proposed a direct optimal construction of TRA-codes.