• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1972-1988
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• 2013

In order to deal with key exposure problem, we introduce forward secure technique into certificateless proxy signature scheme, and propose the formal definition and security model of the forward secure certificateless proxy signature. Our security model takes into account the super adversary in certificateless signature. Furthermore, we present a construction of forward secure certificateless proxy signature scheme with bilinear maps. Based on the difficulty of computational Diffie-Hellman problem, we prove the scheme is secure against chosen message attack in the random oracle model. Finally, we analyze efficiency of the proposed scheme.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.556-558
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• 2008

Secure broadcasting is requirement for payment of TV systems, government or company. Hierarchical key management for access control provides efficient key management in those environment. Also, time-bound hierarchical key management technique generates different keys in each time period. In 2004, Tzeng proposed a time-bound cryptgraphic key assignment scheme for access control in a hierarchy and in 2008, Bertino et al proposed an efficient time-bound hierarchical key management scheme for secure broadcasting. Tzeng's scheme and Bertino et al's scheme are organized in different environment and primitive. In this paper, we analysis above two time-bound hierarchical key management scheme.

• Journal of information and communication convergence engineering
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• v.5 no.1
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• pp.68-72
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• 2007

In this paper, we present robust and secure metering scheme to measure the number of interactions between clients and servers in the web, especially the web advertising. In most cases the web advertising is consists of advertisers, clients, servers, and an audit agency. The metering scheme should always be secure against fraud attempts by servers which maliciously try to inate the number of their visits and against clients that attempt to disrupt the metering process. We propose robust and secure metering scheme based on cryptographic techniques. By analyzing the proposed scheme we show that our scheme is more robust and secure than the previous schemes [1,2,4,5].

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2718-2731
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• 2019

Conjunctive keyword search encryption is an important technique for protecting sensitive data that is outsourced to cloud servers. However, the process of searching outsourced data may facilitate the leakage of sensitive data. Thus, an efficient data search approach with high security is critical. To solve this problem, an efficient conjunctive keyword search scheme based on ciphertext-policy attribute-based encryption is proposed for cloud storage environment. This paper proposes an efficient mechanism for removing the secure channel and resisting off-line keyword-guessing attacks. The storage overhead and the computational complexity are regardless of the number of keywords. This scheme is proved adaptively secure based on the decisional bilinear Diffie-Hellman assumption in the standard model. Finally, the results of theoretical analysis and experimental simulation show that the proposed scheme has advantages in security, storage overhead and efficiency, and it is more suitable for practical applications.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.313-323
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• 2020

With the development of smart grid technologies, a user can use the secure and reliable power services in smart gird environments. However, the users are not secure against various potential attacks because the smart gird services are provided through the public channel. Therefore, a secure and lightweight authentication and key agreement scheme has become a very important security issue in smart grid in order to guarantee user's privacy. In 2019, Zhang et al. proposed a lightweight authentication scheme for smart gird communications. In this paper, we demonstrate that Zhang et al.'s scheme is vulnerable to impersonation and session key disclosure attacks, and then we propose a secure authentication and key agreement scheme for smart grid environments without tamper-resistant devices. Moreover, we perform the informal security and the BAN logic analysis to prove that our scheme is secure various attacks and provides secure mutual authentication, respectively. We also perform the performance analysis compared with related schemes. Therefore, the proposed scheme is efficiently applicable to practical smart gird environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1502-1522
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• 2019

Leakage of secret keys may be the most devastating problem in public key cryptosystems because it means that all security guarantees are missing. The forward security mechanism allows users to update secret keys frequently without updating public keys. Meanwhile, it ensures that an attacker is unable to derive a user's secret keys for any past time, even if it compromises the user's current secret key. Therefore, it offers an effective cryptographic approach to address the private key leakage problem. As an extension of the forward security mechanism in certificate-based public key cryptography, forward-secure certificate-based signature (FS-CBS) has many appealing merits, such as no key escrow, no secure channel and implicit authentication. Until now, there is only one FS-CBS scheme that does not employ the random oracles. Unfortunately, our cryptanalysis indicates that the scheme is subject to the security vulnerability due to the existential forgery attack from the malicious CA. Our attack demonstrates that a CA can destroy its existential unforgeability by implanting trapdoors in system parameters without knowing the target user's secret key. Therefore, it is fair to say that to design a FS-CBS scheme secure against malicious CAs without lying random oracles is still an unsolved issue. To address this problem, we put forward an enhanced FS-CBS scheme without random oracles. Our FS-CBS scheme not only fixes the security weakness in the original scheme, but also significantly optimizes the scheme efficiency. In the standard model, we formally prove its security under the complexity assumption of the square computational Diffie-Hellman problem. In addition, the comparison with the original FS-CBS scheme shows that our scheme offers stronger security guarantee and enjoys better performance.

• The Journal of Information Technology
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• v.2 no.2
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• pp.89-105
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• 1999

In this paper, we present a countermeasure for a various trouble occurred in secure communication of document image. We Propose a security system for transmission of document image using mixing algorithm that the third party cannot conceive secure transmission of information instead of existing scheme which depend on crypto-degree of security algorithm, itself. For this, RM, DM and RDM algorithm for mixing of secure bits are proposed and applied to digital signature for mixing for secure document and mixing for non-secure document by secure document. Security system for document image involves not only security scheme for document image transmission itself, but also digital signature scheme. The transmitter embeds secretly the signatures onto secure document, embeds it to non-secure document and transfers it to the receiver. The receiver makes a check of any forgery on the signature and the document. Because the total amount of transmitted data and the image quality are about the same to those of the original document image, respectively, the third party cannot notice the fact that signatures and secure document are embedded on the document image. Thus, the probability of attack will be reduced.

• International Journal of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.35-43
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• 2017

In 2013, Lee-Lie proposed secure smart card based authentication scheme of Zhu's authentication for TMIS which is secure against the various attacks and efficient password change. In this paper, we discuss the security of Lee-Lie's smart card-based authentication scheme, and we have shown that Lee-Lie's authentication scheme is still insecure against the various attacks. Also, we proposed the improved scheme to overcome these security problems of Lee-Lie's authentication scheme, even if the secret information stored in the smart card is revealed. As a result, we can see that the improved smart card based user authentication scheme for TMIS is secure against the insider attack, the password guessing attack, the user impersonation attack, the server masquerading attack, the session key generation attack and provides mutual authentication between the user and the telecare system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.3280-3298
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• 2019

Vehicular ad-hoc networks (VANETs) have become increasingly significant in intelligent transportation systems, they play a great role in improving traffic safety and efficiency. In the deployment of intelligent VANETs, intelligent vehicles can efficiently exchange important or urgent traffic information and make driving decisions. Meanwhile, secure data communication and vehicle's identity privacy have been highlighted. To cope with these security issues, in this paper, we construct an efficient anonymous authentication scheme with secure communication in intelligent VANETs. Combing the ElGamal encryption technique with a modified Schnorr signature technique, the proposed scheme provides secure anonymous authentication process for encrypted message in the vehicle-to-infrastructure communication model, and achieves identity privacy, forward security, and reply attack resistance simultaneously. Moreover, except the trusted authority (TA), any outside entity cannot trace the real identity of an intelligent vehicle. The proposed scheme is designed on an identity-based system, which can remove the costs of establishing public key infrastructure (PKI) and certificates management. Compared with existing authentication schemes, the proposed scheme is much more practical in intelligent VANETs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4484-4501
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• 2019

In this paper, we put forward a delay-aware secure maximum distance separable (MDS) coded caching scheme to resist the eavesdropping attacks for device-to-device (D2D) content sharing by combining MDS coding with distributed caching. In particular, we define the average system delay to show the potential coupling of delay-content awareness, and learn the secure constraints to ensure that randomly distributed eavesdroppers cannot obtain enough encoded packets to recover their desired contents. Accordingly, we model such a caching problem as an optimization problem to minimize the average system delay with secure constraints and simplify it to its convex relaxation. Then we develop a delay-aware secure MDS coded caching algorithm to obtain the optimal caching policy. Extensive numerical results are provided to demonstrate the excellent performance of our proposed algorithm. Compared with the random coded caching scheme, uniform coded caching scheme and popularity based coded caching scheme, our proposed scheme has 3.7%, 3.3% and 0.7% performance gains, respectively.