• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.87-92
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• 2006

An $AB^2$ modular operation is an efficient basic operation for the public key cryptosystems and various systolic architectures for $AB^2$ modular operation have been proposed. However, these architectures have a shortcoming for cryptographic applications due to their high area complexity. Accordingly, this paper presents an partitioned $AB^2$ systolic modular multiplier over GF($2^m$). A dependency graph from the MSB $AB^2$ modular multiplication algorithm is partitioned into 1/3 to get an partitioned $AB^2$ systolic multiplier. The multiplier reduces the area complexity about 2/3 compared with the previous multiplier. The multiplier could be used as a basic building block to implement the modular exponentiation for the public key cryptosystems based on smartcard which has a restricted hardware requirements.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.189-194
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• 2017

The reversibility of a quantum logic circuit can be realized when two reversible conditions of information reversible and energy reversible circuits are satisfied. In this paper, we have modeled the computation cycle required to recover the information reversibility from the multivalued quantum logic to the original state. For modeling, we used a function embedding method that uses a unitary switch as an arithmetic exponentiation switch. In the quantum logic circuit, if the adjoint gate pair is symmetric, the unitary switch function shows the balance function characteristic, and it takes 1 cycle operation to recover the original information reversibility. Conversely, if it is an asymmetric structure, it takes two cycle operations by the constant function. In this paper, we show that the problem of 2-cycle restoration according to the asymmetric structure when the hybrid MCT gate is realized with the ternary M-S gate can be solved by equivalent conversion of the asymmetric gate to the gate of the symmetric structure.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.23-29
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• 2015

The baby-step giant-step algorithm seeks b in a discrete logarithm problem when a,c,p of $a^b{\equiv}c$(mod p) are already given. It does so by dividing p by m block of $m={\lceil}{\sqrt{p}}{\rceil}$ length and letting one giant walk straight toward $a^0$ with constant m strides in search for b. In this paper, I basically reduce $m={\lceil}{\sqrt{p}}{\rceil}$ to p/l, $a^l$ > p and replace a giant with an adult who is designed to walk straight with constant l strides. I also extend the algorithm to allow $2^k$ adults to walk simultaneously. As a consequence, the proposed algorithm quarters the execution time of the basic adult-walk method when applied to $2^k$, (k=2) in the range of $1{\leq}b{\leq}p-1$. In conclusion, the proposed algorithm greatly shorten the step number of baby-step giant-step.

• Journal of IKEEE
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• v.22 no.3
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• pp.522-531
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• 2018

A public-key cryptography processor EC-RSA was designed, which integrates a 224-bit prime field elliptic curve cryptography (ECC) defined in the FIPS 186-2 as well as RSA with 2048-bit key length into a single hardware structure. A finite field arithmetic core used in both scalar multiplication for ECC and exponentiation for RSA was designed with 32-bit data-path. A lightweight implementation was achieved by an efficient hardware sharing of the finite field arithmetic core and internal memory for ECC and RSA operations. The EC-RSA processor was verified by FPGA implementation. It occupied 11,779 gate equivalents (GEs) and 14 kbit RAM synthesized with a 180-nm CMOS cell library and the estimated maximum clock frequency was 133 MHz. It takes 867,746 clock cycles for ECC scalar multiplication resulting in the estimated throughput of 34.3 kbps, and takes 26,149,013 clock cycles for RSA decryption resulting in the estimated throughput of 10.4 kbps.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.32-43
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• 2010

IPTV is an emerging technology that combines both broadcasting and tele-communication technologies, and provides various multi-media contents to the service subscribers. In general, IPTV broadcasters transmit scrambled signals (multi-media contents) to the paying subscribers, and the users within the acknowledged network descramble the signals using the smart-card. That is, users are verified through communication between STB (Set-Top Box) and smart-card. In 2004, Jiang et al. proposed a secure protocol regarding the verification process. The method has been modified and enhanced by several following research works. However, all the methods that have been proposed so far required modular exponentiation operations which may raise the smart-card costs. In this paper, we propose a new efficient mutual authentication and session-key establishment protocol using only hash functions and exclusive-or operations, and show that the proposed protocol is still secure under various security attacks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7C
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• pp.653-663
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• 2002

The signature-then-encryption based on RSA scheme provides forward secrecy, but requires 4 modulo exponentiation operations in total, and the signcryption scheme proposed by Zheng simultaneously fulfills both the functions of digital signature and symmetric key encryption in a logically single step, and with a computational cost significantly smaller than that required by the current standard signature-then-encryption, but it can not provide forward secrecy. In this paper, we propose an enhanced signcryption scheme which can provide forward secrecy with lower computational cost and lower communication overhead comparing with those of the signature-then-encryption based on RSA, and with a similar communication overhead of Zheng's scheme. The proposed scheme can be also easily modified to the direct signature verification scheme by the recipient without using the recipient's private key. Additionally, we suggest a new design protocol with server-supported signatures which solves the CRLs(Certificate Revocation Lists) burden and provides non-repudiation of origin. This protocol with server-supported signatures also can be applied to the original signcryption scheme proposed by Zheng in order to improve security.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.229-239
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• 2009

To solve user authentication problem, many remote user authentication schemes using password and smart card at the same time have been proposed. Due to the increasing of interest in personal privacy, there were some recent researches to provide user anonymity. In 2004, Das et al. firstly proposed an authentication scheme that guarantees user anonymity using a dynamic ID. In 2005, Chien et al. pointed out that Das et al.'s scheme has a vulnerability for guaranteing user anonymity and proposed an improved scheme. However their authentication scheme was found some weaknesses about insider attack, DoS attack, and restricted replay attack. In this paper, we propose an enhanced scheme which can remove vulnerabilities of Chien et al.'s scheme. The proposed authentication protocol prevented insider attack by using user's Nonce value and removed the restricted replay attack by replacing time stamp with random number. Furthermore, we improved computational efficiency by eliminating the exponentiation operation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1367-1372
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• 2007

This paper suggests One-time Password key exchange authentication technique for a strong authentication based on MANET and through identify wireless environment security vulnerabilities, analyzes current authentication techniques. The suggested authentication technique consists of 3 steps: Routing, Registration, and Running. The Routing step sets a safe route using AODV protocol. The Registration and Running step apply the One-time password S/key and the DH-EKE based on the password, for source node authentication. In setting the Session key for safe packet transmission and data encryption, the suggested authentication technique encrypts message as H(pwd) verifiers, performs key exchange and utilizes One time password for the password possession verification and the efficiency enhancement. EKE sets end to end session key using the DH-EKE in which it expounds the identifier to hash function with the modula exponent. A safe session key exchange is possible through encryption of the H(pwd) verifier. The suggested authentication technique requires exponentiation and is applicable in the wireless network environment because it transmits data at a time for key sharing, which proves it is a strong and reliable authentication technique based on the complete MANET.

• Journal of the Korea Society of Computer and Information
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• v.18 no.8
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• pp.87-93
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• 2013

A baby-step giant-step algorithm divides n by n blocks that possess $m={\lceil}\sqrt{n}{\rceil}$ elements, and subsequently computes and stores $a^x$ (mod n) for m elements in the 1st block. It then calculates mod n for m blocks and identifies each of them with those in the 1st block of an identical elemental value. This paper firstly proposes a modified baby-step giant-step algorithm that divides ${\lceil}m/2{\rceil}$ blocks with m elements applying $a^{{\phi}(n)/2}{\equiv}1(mod\;n)$ and $a^x(mod\;n){\equiv}a^{{\phi}(n)+x}$ (mod n) principles. This results in a 50% decrease in the process of the giant-step. It then suggests a reverse baby-step giant step algorithm that performs and saves ${\lceil}m/2{\rceil}$ blocks firstly and computes $a^x$ (mod n) for m elements. The proposed algorithm is found to successfully halve the memory and search time of the baby-step giant step algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.1
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• pp.11-18
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• 2003

As the Internet moves to mobile environment, one of the most serious problems for the security is to required a new security Protocol with safety and efficiency. To solve the problem. we Propose a new Protocol that reduces the communication franc and solves the problem associated with the private security keys supplied by the trusted third party. The protocol is a non-Interactive oblivious transfer protocol, based on the EIGamal public-key algorithm. Due to its Non-Interactive oblivious transfer protocol, it can effectively reduce communication traffic in server-client environment. And it is also possible to increase the efficiency of protocol through the mechanism that authentication probability becomes lower utilizing a challenge selection bit. The protocol complexity becomes higher because it utilizes double exponentiation. This means that the protocol is difficult rather than the existing discrete logarithm or factorization in prime factors. Therefore this can raise the stability of protocol.