• Communications of the Korean Mathematical Society
• /
• v.24 no.1
• /
• pp.153-159
• /
• 2009

In this paper, we analyze a dynamic threshold decryption scheme proposed by Long et al. It was claimed that the scheme allows to renew the master key, or to add/remove or update a decryption server, without leaking any information on the master key and changing other decryption server's secret keys. We present an attack to Long et al's scheme by using the fact that it renews a decryption server's secret key without changing other decryption server's secret shares.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.12
• /
• pp.6175-6189
• /
• 2019

To slove the security and efficiency problem of anonymous authentication in vehicular ad-hoc network (VANET), we adopt the bilinear pairing theory to propose an identity-based batch anonymous authentication scheme for VANET. The tamper-proof device in the on-board unit and the trusted authority jointly realize the anonymity of vehicle identity and the signature of messages, which further enhances the security of this scheme, as well as reduces the overhead of trusted authority. Batch authentication can improve the efficiency of anonymous authentication for VANET. Security and efficiency analyses demonstrate that this scheme not only satisfies such security properties as anonymity, non-forgeability and non-repudiation, but also has advantage in time and space complexity. Simulation results show that this scheme can achieve good performance in real-time VANET communication.

• Journal of Communications and Networks
• /
• v.15 no.3
• /
• pp.252-257
• /
• 2013

To alleviate the damage caused by key exposures, Dodis et al. introduced the notion of key-insulated security where secret keys are periodically updated by using a physically insulated helper key. To decrease the risk of helper key exposures, Hanaoka et al. advocated parallel key-insulated mechanism where distinct helpers are independently used in key updates. In this paper, we propose the first parallel key-insulated signature scheme which is provably secure without resorting to the random oracle methodology. Our scheme not only allows frequent key updating, but also does not increase the risk of helper key exposures.

• ETRI Journal
• /
• v.34 no.3
• /
• pp.421-428
• /
• 2012

An aggregate signature scheme is a digital signature scheme that allows aggregation of n distinct signatures by n distinct users on n distinct messages. In this paper, we present an aggregate signcryption scheme (ASC) that is useful for reducing the size of certification chains (by aggregating all signatures in the chain) and for reducing message size in secure routing protocols. The new ASC scheme combines identity-based encryption and the aggregation of signatures in a practical way that can simultaneously satisfy the security requirements for confidentiality and authentication. We formally prove the security of the new scheme in a random oracle model with respect to security properties IND-CCA2, AUTH-CMA2, and EUF-CMA.

• Journal of Broadcast Engineering
• /
• v.13 no.1
• /
• pp.79-85
• /
• 2008

An authenticated group key agreement protocol allows a group of parties communicating over an insecure network to share a common secret key. In this paper, we show that Zhou et al.'s ID-based authenticated group key agreement schemes do not provide forward secrecy.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.1
• /
• pp.287-304
• /
• 2022

With the development of quantum computers, ring signature schemes based on large integer prime factorization, discrete logarithm problem, and bilinear pairing are under threat. For this reason, we design a ring signature scheme based on lattice with a fixed verification key. Compared with the previous ring signature scheme based on lattice, our design has a fixed verification key and does not disclose the signer's identity. Meanwhile, we propose an anonymous electronic voting scheme by using our ring signature scheme based on lattice and (t, n) threshold scheme, which makes up for the lack of current anonymous electronic voting that cannot resist attacks of the quantum computer. Finally, under standard model (SM), we prove that our ring signature scheme based on lattice is anonymous against the full-key exposure, and existentially non-forgeable against insider corruption. Furthermore, we also briefly analyze the security of our anonymous electronic voting scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.20 no.2
• /
• pp.1-11
• /
• 2020

As an important basic building block of the smart grid environment, smart meter provides real-time electricity consumption information to the utility. However, ensuring information security and privacy in the smart meter data aggregation process is a non-trivial task. Even though the secure data aggregation for the smart meter has been a lot of attention from both academic and industry researchers in recent years, most of these studies are not secure against internal attackers or cannot provide data integrity. Besides, their computation costs are not satisfactory because the bilinear pairing operation or the hash-to-point operation is performed at the smart meter system. Recently, blockchains or distributed ledgers are an emerging technology that has drawn considerable interest from energy supply firms, startups, technology developers, financial institutions, national governments and the academic community. In particular, blockchains are identified as having the potential to bring significant benefits and innovation for the electricity consumption network. This study suggests a distributed, privacy-preserving, and simple secure smart meter data aggregation system, backed up by Blockchain technology. Smart meter data are aggregated and verified by a hierarchical Merkle tree, in which the consensus protocol is supported by the practical Byzantine fault tolerance algorithm.

• Journal of Internet Computing and Services
• /
• v.14 no.5
• /
• pp.11-26
• /
• 2013

In the wireless Internet, it is so restrictive to use the IPSec. The MIPv4 IPSec's path cannot include wireless links. That is, the IPSec of the wireless Internet cannot protect an entire path of Host-to-Host connection. Also wireless circumstance keeps a path static during the shorter time, nevertheless, the IKE for IPSec SA agreement requires relatively long delay. The certificate management of IPSec PKI security needs too much burden. This means that IPSec of the wireless Internet is so disadvantageous. Our paper is to construct the Mobile IPSec proper to the wireless Internet which provides the host-to-host transport mode service to protect even wireless links as applying excellent WP-IBE scheme. For this, Mobile IPSec requires a dynamic routing over a path with wireless links. FA Forwarding is a routing method for FA to extend the path to a newly formed wireless link. The FA IPSec SA for FA Forwarding is updated to comply the dynamically extended path using Source Routing based Bind Update. To improve the performance of IPSec, we apply efficient and strong future Identity based Weil Pairing Bilinear Elliptic Curve Cryptography called as WP-IBE scheme. Our paper proposes the modified protocols to apply 6 security-related algorithms of WP-IBE into the Mobile IPSec. Particularly we focus on the protocols to be applied to construct ESP Datagram.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.15 no.1
• /
• pp.41-55
• /
• 2005

A group key agreement protocol allows a group of user to share a key which may later be used to achieve certain cryptographic goals. In this paper, we propose a new scalable two-round ID-based group key agreement protocol which would be well fit to a Pay-TV system, additionally. to the fields of internet stock quotes, audio and music deliveries, software updates and the like. Our protocol improves the three round poop key agreement protocol of Nam et al., resulting in upgrading the computational efficiency by using the batch verification technique in pairing-based cryptography. Also our protocol simplifies the key agreement procedures by utilizing ID-based system. We prove the security of our protocol under the Computational Diffie-Hellman assumption and the Bilinear Decisional Diffie-Hellman assumption. Also we analyze its efficiency.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.15 no.4
• /
• pp.11-27
• /
• 2005

To date, most identity-based key agreement protocols are based on a single PKG (Private Key Generator) environment. In 2002, Chen and Kudla proposed an identity-based key agreement protocol for a multiple PKG environment, where each PKG shares identical system parameters but possesses distinct master key. However, it is more realistic to assume that each PKG uses different system parameters including the PKG's master key. In this paper, we propose a new two party key agreement protocol between users belonging to different PKGs that do not share system parameters. We also extend this protocol to two types of tripartite key agreement protocols. We show that our two party protocol requires minimal amount of pairing computation for a multiple PKG environment and our tripartite protocol is more efficient than existing protocols. We also show that the proposed key agreement protocols satisfy every security requirements of key agreement protocol.