Hasegawa Shingo

39Publications

3H-index

52Citations

Publications 34

Newest

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

Multisignatures enable multiple users to sign a message in an interactive manner. Many instantiations are proposed for multisignatures, however, most of them are quantum-insecure, because these are based on the integer factoring assumption or the discrete logarithm assumption. Although there exist some constructions based on the lattice problems, which are believed to be quantum-secure, their security reductions are loose. In this paper, we construct a first lattice-based multisignature which ha...

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (CIT: Center for Information Technology)H-Index: 3

Galindo-Garcia identity-based signature (GG09 IBS) is an efficient identity-based signature (IBS) based on Schnorr signature scheme. The security of GG09 IBS is proven in the random oracle model under the discrete-log assumption, however, the security proof achieves a loose security only. In CANDAR'17, Fukumitsu and Hasegawa proposed a GG09-like IBS (FH17 IBS). Although their scheme achieves a tight security in the random oracle model under the DDH assumption, the size of components and the comp...

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (CIT: Center for Information Technology)H-Index: 3

Galindo and Garcia introduced a light-wight identity-based signature (IBS) based on Schnorr signature in AFRICACRYPT 2009. Despite the simple construction and the ef-ficiency of Galindo-Garcia IBS, to the best of our knowledge, their followers do not appear except the IBS scheme by Fukumitsu and Hasegawa in CANDAR’17. Although their IBS achieves the tight security, the efficiency is worse than Galindo-Garcia IBS. Their result suggests that Galindo-Garcia IBS utilizes some special properties of S...

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

Galindo and Garcia proposed an identity-based signature based on the Schnorr signature. Although their scheme is proven to be secure in the random oracle model, the security reduction is loose. Later, the security reduction is improved by Chatterjee, Kamath and Kumar, however, the reduction is still loose. In this paper, we propose an identity-based signature scheme which is based on the Schnorr signature. Our scheme follows the idea of the construction of the Galindo and Garcia's one. The secur...

A Method for Constructing an Autonomous Decentralized P2P Storage with High Confidentiality and Reliability

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

Last.Masao Sakai (Tohoku University)H-Index: 5

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We have proposed a decentralized Peer-to-Peer (P2P) cloud storage scheme achieving high confidentiality by using a large number of unspecified P2P nodes. There is one crucial problem in the scheme: it is generally difficult to maintain the reliability of the stored data since there is no designated central server which supervises the whole system, and hence, it will be infeasible to certainly restore the stored data if the P2P nodes are to be less reliable. In this paper, we propose a method to ...

Impossibility of the Provable Security of the Schnorr Signature from the One-More DL Assumption in the Non-programmable Random Oracle Model

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

The security of the Schnorr signature was widely discussed. In the random oracle model (ROM), it is provable from the DL assumption, whereas there is a negative circumstantial evidence in the standard model. Fleischhacker, Jager and Schroder showed that the tight security of the Schnorr signature is unprovable from a strong cryptographic assumption, such as the One-more DL (OM-DL) assumption and the computational and decisional Diffie-Hellman assumption, in the ROM via a generic reduction as lon...

Mar 1, 2017 in AINA (Advanced Information Networking and Applications)

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

Last.Daiki Takahashi (Tohoku University)H-Index: 2

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We propose a new secure online storage scheme based on an open P2P network without a central server. In the proposed scheme, attackers cannot detect target user data in the online storage because the user data is divided into some parts by the secret sharing, and they are distributed to P2P nodes via the anonymous communication. The proposed scheme can prevent the direct attack on the target user node because metadata for the reconstruction also hidden in the online storage, hence nothing remain...

Oct 1, 2016 in ISITA (International Symposium on Information Theory and its Applications)

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

We propose a generic construction of tightly secure signature schemes in the non-programmable random oracle model. Our construction employs the dual-mode commitment and the lossy identification schemes. Since there are many instantiation of lossy identification schemes, we can obtain many tightly secure signature schemes in the non-programmable random oracle model.

Oct 1, 2016 in ISITA (International Symposium on Information Theory and its Applications)

#1Hasegawa Shingo (Tohoku University)H-Index: 3

#2Shuji Isobe (Tohoku University)H-Index: 3

Last.Ryo Takahashi (Tohoku University)H-Index: 16

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For the identity-based aggregate signatures, Hohenberger, Sahai and Waters proposed the first scheme that admits unrestricted aggregation, using multilinear maps. On the other hand, for the attribute based-signatures, which is an extended notion of the identity-based signatures, the ones with aggregation are not known to exist so far. This paper studies the attribute-based aggregate signatures. We introduce a rigorous definition of the attribute-based aggregate signatures and propose a construct...

Impossibility on the Provable Security of the Fiat-Shamir-Type Signatures in the Non-programmable Random Oracle Model

#1Masayuki Fukumitsu (Hokkaido Information University)H-Index: 3

#2Hasegawa Shingo (Tohoku University)H-Index: 3

On the security of Fiat-Shamir (FS) type signatures, some negative circumstantial evidences were given in the non-programmable random oracle model (NPROM). Fischlin and Fleischhacker first showed an impossibility for specific FS-type signatures via a single-instance reduction. In ISC 2015, Fukumitsu and Hasegawa found another conditions to prove such an impossibility, however their result requires a strong condition on a reduction, i.e. a key-preserving reduction. In this paper, we focus on a no...

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