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 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 introduce a new functionality for proxy re-encryption (PRE) that we call re-encryption verifiability. In a PRE scheme with re-encryption verifiability (which we simply call verifiable PRE, or VPRE), a receiver of a re-encrypted ciphertext can verify whether the received ciphertext is correctly transformed from an original ciphertext by a(More)