• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.771-780
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• 2020

QKD(Quantum Key Distribution) is one of the protocols that can make two distant parties safely share secure keys against the threat of quantum computer. Generally, cryptographic applications which are connected to the QKD device have fixed roles as a transmitter and a receiver due to the race condition and complexity of implementation. Because the conventional QKD system is mainly applied to the link encryptor, there are no problems even if the roles of the cryptographic devices are fixed. We propose a new scheme of QKD system and protocol that is easy to extend to the QKD network by eliminating quantum key dependency between cryptographic device and QKD node. The secure keys which are generated by the TRNG(True Random Number Generator) are provided to the cryptographic applications instead of quantum keys. We design an architecture to transmit safely the secure keys using the inbound and outbound quantum keys which are shared between two nodes. In this scheme, since the dependency of shared quantum keys between two QKD nodes is eliminated, all cryptographic applicatons can be a master or a slave depending on who initiates the cryptographic communications.

• 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 Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.512-518
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• 2000

Self-certified public keys, introduced by Girault allow the authenticity of public keys to be verified implicitly during the use of the keys. This paper first presents new concept of verifiable self-certified public keys and provides concrete examples satisfying our conditions. Verifiable self-certified public keys combine the benefit of certification-based schemes and Girault's self-certified public keys. Furthermore, we also cryptanalyze Petersen's pseudonymous self-certified keys and present the more secure protocol.

• Journal of Information Processing Systems
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• v.20 no.1
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• pp.116-130
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• 2024

In the Internet-of-Things (IoT) or blockchain-based network systems, secure keys may be stored in individual devices; thus, individual devices should protect data by performing secure operations on the data transmitted and received over networks. Typically, secure functions, such as a physical unclonable function (PUF) and fully homomorphic encryption (FHE), are useful for generating safe keys and distributing data in a network. However, to provide these functions in embedded devices for IoT or blockchain systems, proper inspection is required for designing and implementing embedded system-on-chip (SoC) modules through overhead and performance analysis. In this paper, a virtual platform (SoC VP) was developed that includes a secure key generation module with a PUF and FHE. The SoC VP platform was implemented using SystemC, which enables the execution and verification of various aspects of the secure key generation module at the electronic system level and analyzes the system-level execution time, memory footprint, and performance, such as randomness and uniqueness. We experimentally verified the secure key generation module, and estimated the execution of the PUF key and FHE encryption based on the unit time of each module.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.354-362
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• 2021

The device to device (D2D) communication is an important and emerging area for future cellular networks. It is concerned about all aspect of secure data transmission between end devices along with originality of the data. In this paradigm, the major concerns are about how keys are delivered between the devices when the devices require the cryptographic keys. Another major concern is how effectively the receiver device verifies the data sent by the sender device which means that the receiver checks the originality of the data. In order to fulfill these requirements, the proposed system able to derive a cryptographic key using a single secret key and these derived keys are securely transmitted to the intended receiver with procedure called mutual authentication. Initially, derived keys are computed by applying robust procedure so that any adversary feel difficulties for cracking the keys. The experimental results shows that both sender and receiver can identify themselves and receiver device will decrypt the data only after verifying the originality of the data. Only the devices which are mutually authenticated each other can interchange the data so that entry of the intruder node at any stage is not possible.

• Journal of Korea Multimedia Society
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• v.20 no.5
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• pp.782-790
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• 2017

As most of the recent smart devices have NFC function the NFC mobile coupon will become one of the pervasive NFC applications. We need the secure NFC coupon protocols to issue and use NFC mobile coupon. In this paper, we analyze the security of the previous protocols and point out the problems of security. As the result of analysis, Premium M-coupon Protocol proposed by A. Alshehri and S. Schneider is the most secure but has unnecessary operations. We propose the Modified Premium M-coupon Protocol-1 with the unnecessary operations removed and show this protocol is secure by security analysis. Most of NFC mobile coupon protocols use the cryptography with the shared secret keys. We propose the Modified Premium M-coupon Protocol-2 without the shared secret keys and show this protocol is secure by security analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1350-1355
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• 2011

It is very important issues to protect many system resources using authorized client authentication in distributed client server systems. So it is not enough to prevent unauthorized opponents from attacking our systems that client authentication is performed using only the client's identifier and password. In this paper, we propose a secure authentication database modeling with two authentication keys such as a client authentication key and a server authentication key. The proposed authentication model can be used making high quality of computer security using two authentication keys during transaction processing. The two authentication keys are created by client and server, and are used in every request transaction without user's extra input. Using the proposed authentication keys, we can detect intrusion during authorized client's transaction processing because we can know intrusion immediately through comparing stored authentication keys in client server systems when hackers attack our network or computer systems.

• ETRI Journal
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• v.37 no.4
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• pp.696-706
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• 2015

This paper presents an achievable secure videoconferencing system based on quantum key encryption in which key management can be directly applied and embedded in a server/client videoconferencing model using, for example, OpenMeeting. A secure key management methodology is proposed to ensure both a trusted quantum network and a secure videoconferencing system. The proposed methodology presents architecture on how to share secret keys between key management servers and distant parties in a secure domain without transmitting any secrets over insecure channels. The advantages of the proposed secure key management methodology overcome the limitations of quantum point-to-point key sharing by simultaneously distributing keys to multiple users; thus, it makes quantum cryptography a more practical and secure solution. The time required for the encryption and decryption may cause a few seconds delay in video transmission, but this proposed method protects against adversary attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2394-2406
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• 2016

ABE has become an effective tool for data protection in cloud computing. However, since users possessing the same attributes share the same private keys, there exist some malicious users exposing their private keys deliberately for illegal data sharing without being detected, which will threaten the security of the cloud system. Such issues remain in many current ABE schemes since the private keys are rarely associated with any user specific identifiers. In order to achieve user accountability as well as provide key exposure protection, in this paper, we propose a key-insulated ciphertext policy attribute based encryption with key exposure accountability (KI-CPABE-KEA). In our scheme, data receiver can decrypt the ciphertext if the attributes he owns match with the self-centric policy which is set by the data owner. Besides, a unique identifier is embedded into each user's private key. If a malicious user exposes his private key for illegal data sharing, his identity can be exactly pinpointed by system manager. The key-insulation mechanism guarantees forward and backward security when key exposure happens as well as provides efficient key updating for users in the cloud system. The higher efficiency with proved security make our KI-CPABE-KEA more appropriate for secure data sharing in cloud computing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3608-3628
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• 2017

Several block cipher modes of operation have been proposed in the literature to protect sensitive information. However, different security analysis models have been presented for attacking them. The analysis indicated that most of the current modes of operation are vulnerable to several attacks such as known plaintext and chosen plaintext/cipher-text attacks. Therefore, this paper proposes a secure block cipher mode of operation to thwart such attacks. In general, the proposed mode combines one-time chain keys with each plaintext before its encryption. The challenge of the proposed mode is the generation of the chain keys. The proposed mode employs the logistic map together with a nonce to dynamically generate a unique set of chain keys for every plaintext. Utilizing the logistic map assures the dynamic behavior while employing the nonce guarantees the uniqueness of the chain keys even if the same message is encrypted again. In this way, the proposed mode called SPCBC can resist the most powerful attacks including the known plaintext and chosen plaintext/cipher-text attacks. In addition, the SPCBC mode improves encryption time performance through supporting parallelized implementation. Finally, the security analysis and experimental results demonstrate that the proposed mode is robust compared to the current modes of operation.