• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.11-25
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• 2005

In MIPv6 environment, an important design consideration for public key based binding update protocols is to minimize asymmetric cryptographic operations in mobile nodes with constraint computational power, such as PDAs and cellular phones, For that, public key based protocols such as CAM-DH. SUCV and Deng-Zhou-Bao's approach provides an optimization to offload asymmetric cryptographic operations of a mobile node to its home agent. However, such protocols have some problems in providing the optimization. Especially, CAM-DH with this optimization does not unload all asymmetric cryptographic operations from the mobile node, while resulting in the home agent's vulnerability to denial of service attacks. In this paper, we improve the drawbacks of CAM-DH. Furthermore, we adopt Aura's two hash-based CGA scheme to increase the cost of brute-force attacks searching for hash collisions in the CGA method. The comparison of our protocol with other public key based protocols shows that our protocol can minimize the MN's computation overhead, in addition to providing better manageability and stronger security than other protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.547-556
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• 2003

This paper proposes a novel arithmetic unit over GF(2$^{m}$ ) for low-area elliptic curve cryptographic processor. The proposed arithmetic unit, which is linear feed back shift register (LFSR) architecture, is designed by using hardware sharing between the binary GCD algorithm and the most significant bit (MSB)-first multiplication scheme, and it can perform both division and multiplication in GF(2$^{m}$ ). In other word, the proposed architecture produce division results at a rate of one per 2m-1 clock cycles in division mode and multiplication results at a rate of one per m clock cycles in multiplication mode. Analysis shows that the computational delay time of the proposed architecture, for division, is less than previously proposed dividers with reduced transistor counts. In addition, since the proposed arithmetic unit does not restrict the choice of irreducible polynomials and has regularity and modularity, it provides a high flexibility and scalability with respect to the field size m. Therefore, the proposed novel architecture can be used for both division and multiplication circuit of elliptic curve cryptographic processor. Specially, it is well suited to low-area applications such as smart cards and hand held devices.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.8
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• pp.453-464
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• 2004

In order to solve the well-known drawback of reduced flexibility that is associate with ASIC implementations, this paper proposes a novel arithmetic unit over GF(2$^{m}$ ) for field programmable gate arrays (FPGAs) implementations of elliptic curve cryptographic processor. The proposed arithmetic unit is based on the binary extended GCD algorithm and the MSB-first multiplication scheme, and designed as systolic architecture to remove global signals broadcasting. The proposed architecture can perform both division and multiplication in GF(2$^{m}$ ). In other word, when input data come in continuously, it produces division results at a rate of one per m clock cycles after an initial delay of 5m-2 in division mode and multiplication results at a rate of one per m clock cycles after an initial delay of 3m in multiplication mode respectively. Analysis shows that while previously proposed dividers have area complexity of Ο(m$^2$) or Ο(mㆍ(log$_2$$^{m}$ )), the Proposed architecture has area complexity of Ο(m), In addition, the proposed architecture has significantly less computational delay time compared with the divider which has area complexity of Ο(mㆍ(log$_2$$^{m}$ )). FPGA implementation results of the proposed arithmetic unit, in which Altera's EP2A70F1508C-7 was used as the target device, show that it ran at maximum 121MHz and utilized 52% of the chip area in GF(2$^{571}$ ). Therefore, when elliptic curve cryptographic processor is implemented on FPGAs, the proposed arithmetic unit is well suited for both division and multiplication circuit.

• Journal of the Institute of Convergence Signal Processing
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• v.1 no.2
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• pp.177-185
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• 2000

In this paper CPLD design of cryptographic coprocessor which implements SEED algorithm is described. To satisfy trade-off between area and speed, the coprocessor has structure in which 1 round operation is divided into three subrounds and then each subround is executed using one clock. To improve clock frequency, online precomputation scheme for round key is used. To apply the coprocessor to various applications, four operating modes such as ECB, CBC, CFB, and OFB are supported. The cryptographic coprocessor is designed using Altera EPF10K100GC503-3 CPLD device and its operation is verified by encryption or decryption of text files through ISA bus interface. It consists of about 29,300 gates and performance of CPLD chip is about 44 Mbps encryption or decryption rate under 18 Mhz clock frequency and ECB mode.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.2
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• pp.135-145
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• 2002

Active networks represent a new approach to network architecture. Nodes(routers, switches, etc.) can perform computations on user data, while packets can carry programs to be executed on nodes and potentially change the state of them. While active networks provide a flexible network iufrastructure, they are more complex than traditional networks and raise considerable security problems. Nodes are Public resources and are essential to the proper and contract running of many important systems. Therefore, security requirements placed upon the computational environment where the code of packets will be executed must be very strict. Trends of research for active network security are divided into two categories: securing active nodes and securing active packets. For example, packet authentication or monitoring/control methods are for securing active node, but some cryptographic techniques are for the latter. This paper is for transferring active packets securely between active nodes. We propose a new method that can transfer active packets to neighboring active nodes securely, and execute executable code included in those packets in each active node. We use both public key cryptosystem and symmetric key cryptosystem in our scheme

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.1
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• pp.29-37
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• 2014

In this paper we show that a dynamic ID authentication scheme using smart cards proposed by Tsai et al. is not secure against DoS attack and insider attack. Further we claim that their scheme may raise a security problem when a user changes his/her password. Then we come up with a security-enhanced version only with small additional computational cost. Our scheme is based on the security of cryptographic hash function and the infeasibility assumption of discrete logarithm problem. In addition, we provide details of security and computational cost analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.2292-2309
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• 2017

Ciphertext policy attribute-based encryption (CP-ABE) is a useful cryptographic technology for guaranteeing data confidentiality but also fine-grained access control. Typically, CP-ABE can be divided into two classes: small universe with polynomial attribute space and large universe with unbounded attribute space. Since the learning with errors over rings (R-LWE) assumption has characteristics of simple algebraic structure and simple calculations, based on R-LWE, we propose a small universe CP-ABE scheme to improve the efficiency of the scheme proposed by Zhang et al. (AsiaCCS 2012). On this basis, to achieve unbounded attribute space and improve the expression of attribute, we propose a large universe CP-ABE scheme with the help of a full-rank differences function. In this scheme, all polynomials in the R-LWE can be used as values of an attribute, and these values do not need to be enumerated at the setup phase. Different trapdoors are used to generate secret keys in the key generation and the security proof. Both proposed schemes are selectively secure in the standard model under R-LWE. Comparison with other schemes demonstrates that our schemes are simpler and more efficient. R-LWE can obtain greater efficiency, and unbounded attribute space means more flexibility, so our research is suitable in practices.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.245-251
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• 2014

Mix network plays a key role in electronic voting to preserve anonymity and lots of mixnet schemes have been proposed so far. However, they requires complex and costly zero-knowledge proofs to provide their correct mixing operations. In 2010, Seb$\acute{e}$ et al. proposed an efficient and lightweight mixnet scheme based on a cryptographic secure hash function instead of zero-knowledge proofs. In this paper, we present a more efficient and faster mixnet scheme than Seb$\acute{e}$ et al.'s scheme under the same assumption. Also, our scheme is secure.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.6
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• pp.288-295
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• 2005

Multi-signcryption scheme is an extension of signcryption scheme for multi-signers performing together the signcryption operation on messages, and it provides useful cryptographic functions such as confidentiality and authenticity for the sound circulation of messages through the Internet. In this paper, we show the weaknesses of the previous multi-signcryption schemes. And then we propose a new multi-signcryption scheme that improves the weaknesses and the efficiency of the previous schemes. Our scheme efficiently provides message flexibility, order flexibility, message verifiability, order verifiability, message confidentiality, message unforgeability, non-repudiation and robustness. Therefore, it is suitable for protecting messages and multi-signers from malicious attacks in the Internet.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.9
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• pp.487-493
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• 2003

A secret sharing scheme is a cryptographic Protocol that a dealer distributes shares about a secret to many participants and authorized subsets of the participants can reconstruct the secret. Secret sharing schemes that reflect various access structure were proposed. We propose a new reusable secret sharing scheme in a hierarchical group. Participants have priority about restoration of secret from high position level of tree. And when participants who belong in high position level are absent, they can delegate restoration competence of the secret transmitting delegation ticket to child nodes that it belongs in low rank level. By participants reuse own share and take part in different secret restoration, they who belong on hierarchical group can be possible different secret restoration by each participant's single share.