• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1714-1725
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• 2003

In this paper we propose reliable billing schemes between users and contents providers where a user is provided value­added service for a paid contents using mobile terminals. Our schemes support various types of services such as short messages, bell sounds, images or music data transmissions, and games in mobile communication environments. Using hash chain method, we also reduced the computational overhead of mobile terminals and the volume of data transmitted between the user and the content provider. Content providers can save memory space because they don't need to store each user's usage evidence but still can charge.

• The KIPS Transactions:PartC
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• v.10C no.6
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• pp.755-762
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• 2003

For the route optimization in the MIPv6, MN(Mobile Node) sends CN(Correspondent Node) a binding update message to notify the binding of is HoA(Home Address) with its new CoA(Care-of Address). However, unautenticated binding updates expose the involved MN and CM to various sucurity attacks. Thus, protecting the binding update process becomes of paramount importance in the MIPv6, and several secure binding update protocols, and the performance of packet exchanges and cryptographic operations. Then, we analyze the four typical binding update protocols based on the presented criterions. In addition, we propose some improvement tips for secure binding updates.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.4
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• pp.213-219
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• 2002

A secret sharing scheme is a kind of cryptographic protocol to maintain secret information by splitting it to many small pieces of shares and sharing between shareholders. In case of shareholders having different authorization to reconstruct the original secret, it is required a new secret sharing scheme to reflect any hierarchical structure between shareholders. In this paper, we propose a new weighted secret sharing scheme, that is, each shareholder has a weight according to the authorization of reconstructing the secret and an access set which is a subset of shareholders can reconstruct the secret if the sum of weights is equal or greater than a predefined threshold.

• ETRI Journal
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• v.44 no.6
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• pp.903-914
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• 2022

Mobile and telecommunication networking uses temporary and random identifiers (IDs) to protect user privacy. For greater intelligence and security o the communications between the core network and the mobile user, we design and build a dynamic randomization scheme for the temporary IDs for mobile networking, including 5G and 6G. Our work for ID randomization (ID-RZ) advances the existing state-of-the-art ID re-allocation approach in 5G in the following ways. First, ID-RZ for ID updates is based on computing, as opposed to incurring networking for the re-allocation-based updates, and is designed for lightweight and low-latency mobile systems. Second, ID-RZ changes IDs proactively (as opposed to updating based on explicit networking event triggers) and provides stronger security (by increasing the randomness and frequency of ID updates). We build on the standard cryptographic primitives for security (e.g., hash) and implement our dynamic randomization scheme in the 5G networking protocol to validate its design purposes, which include time efficiency (two to four orders of magnitude quicker than the re-allocation approach) and appropriateness for mobile applications.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.5
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• pp.396-403
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• 2009

An anonymous asymmetric fingerprinting protocol combined with watermarking techniques, is one of the copyright protection technologies keeping both right of a seller and that of a buyer, where a seller and an anonymous buyer perform such a protocol that employs various cryptographic tools in order that the seller does not know the exact watermarked copy that the buyer receives, while inserting an invisible non-removable fingerprint i.e., each different unique watermark, into each copy of the digital content to be sold. In such a protocol innocent buyers are kept anonymous during transactions, however, the unlawful reseller is unambiguously identified with a real identity as a copyright violator. In 2007, Yong and Lee proposed an anonymous asymmetric fingerprinting scheme with trusted third party. In this paper we point out the weakness of their scheme such as: the buyer with intention can remove the fingerprint in the watermarked content, because he/she can decrypt the encrypted fingerprint with a symmetric key using man-in-the-middle-attack; a real identity of a buyer can be revealed to the seller through the identification process even though he/she is honest. Furthermore, we propose an improved secure and efficient anonymous asymmetric fingerprinting scheme which enables to reduce the number of communication between the participants.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1083-1091
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• 2017

This paper describes a design of cryptographic processor supporting 224-bit elliptic curves over prime field defined by NIST. Scalar point multiplication that is a core arithmetic function in elliptic curve cryptography(ECC) was implemented by adopting the modified Montgomery ladder algorithm. In order to eliminate division operations that have high computational complexity, projective coordinate was used to implement point addition and point doubling operations, which uses addition, subtraction, multiplication and squaring operations over GF(p). The final result of the scalar point multiplication is converted to affine coordinate and the inverse operation is implemented using Fermat's little theorem. The ECC processor was verified by FPGA implementation using Virtex5 device. The ECC processor synthesized using a 0.18 um CMOS cell library occupies 2.7-Kbit RAM and 27,739 gate equivalents (GEs), and the estimated maximum clock frequency is 71 MHz. One scalar point multiplication takes 1,326,985 clock cycles resulting in the computation time of 18.7 msec at the maximum clock frequency.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.119-131
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• 2009

The world's widely used key exchange protocols are open cryptographic communication protocols, such as TLS/SSL, whereas in the financial field in Korea, key exchange protocols developed by industrial classification group have been used that are based on PKI(Public Key Infrastructure) which is suitable for the financial environments of Korea. However, the key exchange protocols are not only vulnerable to client impersonation attacks and known-key attacks, but also do not provide forward secrecy. Especially, an attacker with the private keys of the financial security server can easily get an old session-key that can decrypt the encrypted messages between the clients and the server. The exposure of the server's private keys by internal management problems, etc, results in a huge problem, such as exposure of a lot of private information and financial information of clients. In this paper, we analyze the weaknesses of the cryptographic communication protocols in use in Korea. We then propose two key exchange protocols which reduce the replacement cost of protocols and are also secure against client impersonation attacks and session-key and private key reveal attacks. The forward secrecy of the second protocol is reduced to the HDH(Hash Diffie-Hellman) problem.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.4 s.304
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• pp.25-32
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• 2005

The spread of mobile devices, PDAs and sensors has enabled the construction of ubiquitous computing environments, transforming regular physical spaces into 'Smart space' augmented with intelligence and enhanced with services. However, the deployment of this computing paradigm in real-life is disturbed by poor security, particularly, the lack of proper authentication and authorization techniques. Also, it is very important not only to find security measures but also to preserve user privacy in ubiquitous computing environments. In this Paper, we propose efficient user authentication and authorization model with anonymity for the privacy-preserving for ubiquitous computing environments. Our model is suitable for distributed environments with the computational constrained devices by using MAC-based anonymous certificate and security association token instead of using Public key encryption technique. And our Proposed Protocol is better than Kerberos system in sense of cryptographic computation processing.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.3
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• pp.161-168
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• 2002

A secret sharing scheme is a cryptographic protocol to share a secret among a set of participants P in the way that only qualified subsets of P can reconstruct the secret whereas any other subset of P, non-qualified to know the secret, cannot determine anything about the secret. In this paper, we propose a new secret sharing scheme in hierarchical groups, whose hierarchy can be represented as a tree structure. In the tree structure, participants of higher levels have priorities to reconstruct the secret over participants of lower levels. In the absence of the participant of a higher level, it is possible for this participant to delegate the ability to reconstruct the secret to the child nodes of the next lower level through the transfer of his delegation ticket. This scheme has a dynamic access structure through the recursive delegation process from the root to lower levels where participants aren't absent.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.4 s.334
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• pp.29-36
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• 2005

This paper presents the first hardware design of ARIA that KSA(Korea Standards Association) decided as the block encryption standard at Dec. 2004. The ARIA cryptographic algorithm has an efficient involution SPN (Substitution Permutation Network) and is immune to known attacks. The proposed ARIA design based on 1 cycle/round include a dual port ROM to reduce a size of circuit md a high speed round key generator with barrel rotator. ARIA design proposed is implemented with Xilinx VirtexE-1600 FPGA. Throughput is 437 Mbps using 1,491 slices and 16 RAM blocks. To demonstrate the ARIA system operation, we developed a security system cyphering video data of communication though Internet. ARIA addresses applications with high-throughput like data storage and internet security protocol (IPSec and TLS) as well as IC cards.