• Journal of Communications and Networks
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• v.13 no.5
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• pp.428-441
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• 2011

A trace-and-revoke scheme is a type of broadcast encryption scheme for content protection on various platforms such as pay-per-view TV and DVD players. In 2006, Boneh and Waters (BW) presented a fully collusion-resistant trace-and-revoke scheme. However, a decisive drawback of their scheme is to require composite-order groups. In this paper, we present a new trace-and-revoke scheme that works in prime-order groups. Our scheme is fully collusion-resistant and achieves ciphertexts and private keys of size O($\sqrt{N}$) for N users. For the same level of security, our scheme is better than the BW scheme in all aspects of efficiency. Some superior features include 8.5 times faster encryption, 12 times faster decryption, and 3.4 times shorter ciphertexts. To achieve our goal, we introduce a novel technique where, by using asymmetric bilinear maps in prime-order groups, the cancellation effect same as in composite-order groups can be obtained.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.1
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• pp.17-30
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• 2016

In this paper, we propose an efficient public key trace and revoke scheme. An trace and revoke scheme is a broadcast encryption scheme which has a tracing and revocation algorithm. It would maintain security of the scheme to revoke pirate keys which are colluded by malicious users. In addition, property of revocation can be applied to various circumstances because it can help cipher text delivered to certain users who are supposed to. In this paper, we would change the scheme[Augmented broadcast encryption scheme] based on the bilinear groups of the composite order into that of prime order and we can improve the size of public key, secret key, ciphertext considerably. Furthermore, we define property of revocation precisely, so we can obtain the result that the scheme with limited revocation can be expanded to have a full revocation. This paper can be easily applied to the organization such as government, military, which has a hierarchical structure.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.46-56
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• 2012

Traitor Tracing schemes are broadcast encryption systems where at least one of the traitors who were implicated in the construction of a pirate decoder can be traced. This traceability is required in various contents delivery system like satellite broadcast, DMB, pay-TV, DVD and so on. In this paper, we propose a public key traitor tracing scheme with key-update method. If the system manager can update a secret key which is stored in an authorized decode, it makes a pirate decoder useless by updating a secret key A pirate decoder which cannot update a secret key does not decrypt contents in next session or during tracing a traitor, this scheme has merits which will make a pirate decoder useless, therefore this scheme raises the security to a higher level.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.5
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• pp.795-807
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• 2014

Vehicular Ad hoc Network (VANET) has gone through a rich amount of research and currently is making its way towards the deployment. However, surprisingly it evolved to rather more applications and services-rich breed referred to as VANET-based clouds due to the advancements in the automobile and communication technologies. Security and privacy have always been the challenges for the think tanks to deploy this technology on mass scale. It is even worse that some security issues are orthogonally related to each other such as privacy, revocation and route tracing. In this paper, we aim at a specific VANET-based clouds framework proposed by Hussain et al. namely VANET using Clouds (VuC) where VANET and cloud infrastructure cooperate with each other in order to provide VANET users (more precisely subscribers) with services. We specifically target the aforementioned conflicted privacy, route tracing, and revocation problem in VANET-based clouds environment. We propose a multiple pseudonymous approach for privacy reasons and leverage the beacons stored in the cloud infrastructure for both route tracing and revocation. In the proposed scheme, revocation authorities after colluding, can trace the path taken by the target node for a specified timespan and can also revoke the identity if needed. Our proposed scheme is secure, conditional privacy preserved, and is computationally less expensive than the previously proposed schemes.