Key Laboratory of Cryptographic Technology and Information Security

Jinan, China

Key Laboratory of Cryptographic Technology and Information Security

Jinan, China

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Yu J.,Qingdao University | Hao R.,Qingdao University | Kong F.-Y.,Shandong University | Kong F.-Y.,Key Laboratory of Cryptographic Technology and Information Security | And 2 more authors.
Ruan Jian Xue Bao/Journal of Software | Year: 2010

The formal security model of forward-secure multi-signature is examined and a forward-secure multi-signature scheme with provable security is proposed. Even if the current secret keys of all the signers are exposed, all the signatures pertaining to previous periods are still valid in this scheme. The presented scheme has proven to be secure in the standard model. © by Institute of Software, the Chinese Academy of Sciences. All rights reserved.


Yu J.,Qingdao University | Kong F.-Y.,Shandong University | Kong F.-Y.,Key Laboratory of Cryptographic Technology and Information Security | Cheng X.-G.,Qingdao University | And 2 more authors.
Ruan Jian Xue Bao/Journal of Software | Year: 2010

An intrusion-resilient signature scheme with provable security is presented in this paper. The scheme has a stronger security than a forward secure signature scheme and a key-insulated signature scheme. It satisfies that signatures in other time periods are secure even after arbitrarily many compromises of base and signer, as long as the compromises do not happen simultaneously. Furthermore, the intruder cannot generate signatures pertaining to previous time periods, even if she compromises base and signer simultaneously to get their secret information. The scheme has a nice average performance. There is no cost parameter for key generation time, base (user) key updating time, base (user) key refresh time, signing time, verifying time, signature size, public key size, and base (user) storage size having a complexity more than O(logT) in this scheme. At last, this scheme is proven secure in the random oracle model, assuming CDH problem is hard. © by Institute of Software, the Chinese Academy of Sciences. All rights reserved.


Yu J.,Qingdao University | Kong F.-Y.U.,Shandong University | Kong F.-Y.U.,Key Laboratory of Cryptographic Technology and Information Security | Cheng X.-G.,Qingdao University | And 2 more authors.
Journal of Information Science and Engineering | Year: 2011

Forward-secure signatures can be used to limit the damage of secret key exposure for digital signatures. In a forward-secure signature scheme, the exposure of current secret key doesn't affect the security of signatures generated in previous periods. In order to integrate this primitive into standard security architectures, Boyen et al. presented a forward-secure signature scheme with untrusted update in the standard model. In this study, we propose another forward-secure signature scheme with untrusted update in the random oracle model. Compared with Boyen's scheme, this scheme has shorter public key, secret key and better key generation algorithm, update algorithm, encrypted key verifying algorithm and signing algorithm. At last, we prove that the scheme is update secure and forward secure under CDH assumption in the random oracle model.


Yu J.,Qingdao University | Kong F.,Shandong University | Kong F.,Key Laboratory of Cryptographic Technology and Information Security | Hao R.,Qingdao University | And 2 more authors.
Jisuanji Yanjiu yu Fazhan/Computer Research and Development | Year: 2010

The secret key exposure is a serious problem for the security of the digital signature. Unfortunately, for a regular digital signature, if the secret key is exposed, all the signatures previously signed are invalid because the verifier cannot identify whether a signature is produced before key exposure or not. Therefore, how to deal with the problem of secret key exposure in signatures is very important. Forward secure threshold signature is an important distributed signature to deal with this problem. It inherits the advantages of forward secure signature and threshold signature. The secret key is renewed periodically through the shares that the players hold, while the public key is fixed during the whole time periods. This kind of signature makes it more difficult for an adversary to compromise the security of the signature: if an adversary cannot attack a quorum number of players, he can't forge any signature; if an adversary can attack a quorum number of players in a certain time period, he can't forge any signature of previous time periods. In 2007, Peng et al. proposed a forward secure threshold signature scheme from bilinear pairing. Analyzed in this paper is the security of Peng et al.'s scheme. Several techniques of security attack are given and it is pointed out that their scheme is insecure. At the same time, some improvement methods are also given.


Yu J.,Qingdao University | Hao R.,Qingdao University | Kong F.,Shandong University | Kong F.,Key Laboratory of Cryptographic Technology and Information Security | And 3 more authors.
Information Sciences | Year: 2011

The security of traditional identity-based signatures wholly depends on the security of secret keys. Exposure of secret keys requires reissuing all previously assigned signatures. This limitation becomes more obvious today as key exposure is more common with increasing use of mobile and unprotected devices. Under this background, mitigating the damage of key exposure in identity-based signatures is an important problem. To deal with this problem, we propose to integrate forward security into identity-based signatures. In this paper, we firstly formalize the definition and security notions for forward-secure identity-based signature scheme, and then construct an efficient scheme. All parameters in our scheme have, at most, log-squared complexity in terms of the total number of time periods. The scheme is provably secure without random oracles. © 2010 Elsevier Inc. All rights reserved.


Yu J.,Qingdao University | Kong F.,Shandong University | Kong F.,Key Laboratory of Cryptographic Technology and Information Security | Cheng X.,Qingdao University | And 2 more authors.
Information Sciences | Year: 2014

Forward-secure signatures are proposed to deal with the key exposure problem. Compared to regular signatures, forward-secure signatures have a special update algorithm that can evolve the new private key in each time period. Therefore, it can protect the security of signatures previous to the time period of key exposure. The efficiency is an important issue of forward-secure signatures. In this paper, we construct a new forward-secure signature scheme using bilinear maps. In this scheme, all performance parameters have complexities of log magnitude in terms of the total time periods. In addition, our scheme needs very few (only triple) pairing operations in the verifying algorithm, which is very important because the pairing operation is very time-consuming. This scheme is proved to be forward secure in the random oracle model assuming the CDH problem is hard. Finally, we give some applications of this scheme including constructing an intrusion-resilient signature scheme and constructing a forward-secure threshold signature scheme. © 2014 Elsevier Inc. All rights reserved.

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