Yutaka Kawai

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Secret handshake allows two members in the same group to authenticate each other secretly. In previous works of secret handshake schemes, two types of anonymities against the group authority (GA) of a group G are discussed: 1)Even GA cannot identify members, namely nobody can identify them (No-Traceability), 2)Only GA can identify members (Traceability). In(More)
In this paper, we propose a reasonable definition of predicate-hiding inner product encryption (IPE) in a public key setting, which we call inner product encryption with ciphertext conversion (IPE-CC), where original ciphertexts are converted to predicate-searchable ones by an helper in possession of a conversion key. We then define a notion of full(More)
In this paper, we introduce a general notion of functional proxy-re-encryption (F-PRE), where a wide class of functional encryption (FE) is combined with proxy-re-encryption (PRE) mechanism. The PRE encryption system should reveal minimal information to a proxy, in particular, hiding parameters of re-encryption keys and of original ciphertexts which he(More)
In this paper, we discuss the strong attack model security for public key encryption scheme and digital signature scheme. Recently, Barbosa and Farshim introduced strong chosen ciphertext attack (SCCA) which is stronger than chosen ciphertext attack. The main motivation of this paper is to find an essential mechanism of secure schemes under strong attack(More)
This paper describes practical file access applications based on SAGA -- A <u>S</u>imple <u>A</u>PI for <u>G</u>rid <u>A</u>pplications-- for distributed storage resources over multi-file-system middleware. SAGA provides a high-level programming interface to bridge between network file-system middleware as(More)