ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 13 Oct 2024 17:18:56 GMT2024-10-13T17:18:56Z50251- New construction of algebraic-geometry codeshttps://scholarbank.nus.edu.sg/handle/10635/43052Title: New construction of algebraic-geometry codes
Authors: Niederreiter, H.; Xing, C.; Lam, K.Y.
Abstract: We present a new construction of linear codes based on algebraic geometry. An important feature of this construction is that we can use places of arbitrary degrade and not just rational places as in Goppa's construction. Examples show that this leads to various improvements on Goppa's construction.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430521999-01-01T00:00:00Z
- A fast algorithm for determining the linear complexity of a sequence with period p n over G F (q)https://scholarbank.nus.edu.sg/handle/10635/39066Title: A fast algorithm for determining the linear complexity of a sequence with period p n over G F (q)
Authors: Xiao, G.; Wei, S.; Lam, K.Y.; Imamura, K.
Abstract: A fast algorithm is presented for determining the linear complexity of a sequence with period p n over GF (q), where p is an odd prime, and where q is a prime and a primitive root (mod p 2). © 2000 IEEE.
Sat, 01 Jan 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/390662000-01-01T00:00:00Z
- The Weight Distribution of C5(1, n)https://scholarbank.nus.edu.sg/handle/10635/39215Title: The Weight Distribution of C5(1, n)
Authors: Lam, K.Y.; Sica, F.
Abstract: In [2] the codes Cq(r, n) over double-struck F signq were introduced. These linear codes have parameters [2n, ∑i=0 r (i n), 2n-r], can be viewed as analogues of the binary Reed-Muller codes and share several features in common with them. In [2], the weight distribution of C3(1, n) is completely determined. In this paper we compute the weight distribution of C5(1, n). To this end we transform a sum of a product of two binomial coefficients into an expression involving only exponentials and Lucas numbers. We prove an effective result on the set of Lucas numbers which are powers of two to arrive to the complete determination of the weight distribution of C5(1, n). The final result is stated as Theorem 2.
Mon, 01 Jan 2001 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/392152001-01-01T00:00:00Z
- Securing digital signatures for non-repudiationhttps://scholarbank.nus.edu.sg/handle/10635/38877Title: Securing digital signatures for non-repudiation
Authors: Zhou, J.; Lam, K.Y.
Abstract: Dispute of transactions is a common problem that could jeopardize business. Hence non-repudiation services are essential in business transactions which provide evidence to enable dispute resolution. To be eligible as non-repudiation evidence, the digital signature on an electronic document should remain valid until its expiry date which is specified by some non-repudiation policy. The conventional approaches are either inefficient or insecure to achieve non-repudiation in electronic commerce. This article presents a practical scheme to secure digital signatures as non-repudiation evidence with an adjustable degree of risk.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/388771999-01-01T00:00:00Z
- Mobile IP registration protocol: a security attack and new secure minimal public-key based authenticationhttps://scholarbank.nus.edu.sg/handle/10635/38876Title: Mobile IP registration protocol: a security attack and new secure minimal public-key based authentication
Authors: Sufatrio, Kwok Yan Lam
Abstract: The ubiquity of the Internet and explosive growth in wireless networking in recent years increasingly urge the demand to support mobility within the Internet, which is what Mobile IP aims to provide. This paper is concerned with the security aspect of the registration protocol in Mobile IP. In this paper, we show that despite the use of authenicated registration messages and replay protection, the current registration protocol suffers from a possible replay attack. The paper also analyzes a proposed extension of Mobile IP that aims to provide public-key based authentication. We show some drawbacks in its protocol design and then propose our own new secure authentication protocol that employs only minimal use of public key cryptography. Despite its practicality, our new protocol provides a scalable solution for authentication and non-repudiation, while sets only minimal computing and administration cost on the Mobile Node.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/388761999-01-01T00:00:00Z
- Sequences with almost perfect linear complexity profiles and curves over finite fieldshttps://scholarbank.nus.edu.sg/handle/10635/43037Title: Sequences with almost perfect linear complexity profiles and curves over finite fields
Authors: Xing, C.; Lam, K.Y.
Abstract: For stream ciphers, we need to generate pseudorandom sequences which are of properties of unpredictability and randomness. A important measure of unpredictability and randomness is the linear complexity profile (l.c.p.) l a(n) of a sequence a. A sequence a is called almost perfect if the l.c.p. is l a(n) = n/2+O(1). Based on curves over finite fields, we present in this correspondence a method to construct almost perfect sequences. We also illustrate our construction by explicit examples from the projective line and elliptic curves over the binary field.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430371999-01-01T00:00:00Z
- Cnstructions of authentication codes from algebraic curves over finite fieldshttps://scholarbank.nus.edu.sg/handle/10635/43054Title: Cnstructions of authentication codes from algebraic curves over finite fields
Authors: Xing, C.; Wang, H.; Lam, K.Y.; Xing, C.P.
Abstract: We present a new application of algebraic curves over finite fields to the constructions of universal hash families and unconditionally secure codes. We show that the constructions derived from the Garcia-Stichtenoth curves yield new classes of authentication codes and universal hash families which are substantially better than those previously known. ©2000 IEEE.
Sat, 01 Jan 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430542000-01-01T00:00:00Z
- Constructions of algebraic-geometry codeshttps://scholarbank.nus.edu.sg/handle/10635/43040Title: Constructions of algebraic-geometry codes
Authors: Xing, C.; Niederreiter, H.; Lam, K.Y.
Abstract: Based on curves over finite fields with many rational points, we present two constructions of linear codes from local expansions of functions at a fixed rational point. It turns out that codes from our constructions have the same bound on their parameters as Goppa's geometry codes. Furthermore, we prove that our second construction is equivalent to Goppa's construction. Finally, an additional construction of linear codes from maximal curves shows that these codes have better parameters than Goppa's geometry codes from maximal curves for a certain interval of parameters.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430401999-01-01T00:00:00Z
- A generalization of algebraic-geometry codeshttps://scholarbank.nus.edu.sg/handle/10635/43009Title: A generalization of algebraic-geometry codes
Authors: Xing, C.; Niederreiter, H.; Lam, K.Y.
Abstract: In this correspondence a generalization of algebraic-geometry codes based on function fields over finite fields with many places of small degree is presented. It turns out that many good linear codes can be obtained from these generalized algebraic-geometry codes. In particular, we calculate some examples of q-ary linear codes for q = 2, 3, 5. These examples show that many best possible linear codes can be found from our construction. © 1999 IEEE.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430091999-01-01T00:00:00Z
- Construction and enumeration of all binary duadic codes of length pmhttps://scholarbank.nus.edu.sg/handle/10635/43014Title: Construction and enumeration of all binary duadic codes of length pm
Authors: Ding, C.; Lam, K.Y.; Xing, C.
Abstract: In this paper we present a binary-tree approach to the construction of all binary duadic codes of length n = pm. We also calculate the number of binary duadic codes of length n = pm, where p = ± 1 (mod 8) is a prime.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430141999-01-01T00:00:00Z
- Constructions of sequences with almost perfect linear complexity profile from curves over finite fieldshttps://scholarbank.nus.edu.sg/handle/10635/43016Title: Constructions of sequences with almost perfect linear complexity profile from curves over finite fields
Authors: Xing, C.; Niederreiter, H.; Lam, K.Y.; Ding, C.
Abstract: Sequences with almost perfect linear complexity profile are of importance for the linear complexity theory of sequences. In this paper we present several constructions of sequences with almost perfect linear complexity profile based on algebraic curves over finite fields. Moreover, some interesting consequences and examples are derived from our constructions. © 1999 Academic Press.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/430161999-01-01T00:00:00Z
- A cardinalised binary representation for exponentiationhttps://scholarbank.nus.edu.sg/handle/10635/52744Title: A cardinalised binary representation for exponentiation
Authors: Lam, K.-Y.; Sung, K.; Hui, L.C.-K.
Abstract: This paper introduces the Cardinalised Binary Representation (CBR) of integers. A family of algorithms for converting binary integers to their CBR equivalents is described. Characteristics of the resulting representation is analyzed and exploited to achieve performance improvement for large integer exponentiation operations. This paper demonstrates that the CBR is a more general scheme than the well known Binary Redundant Representation (BRR) [1], and shows that both software and hardware CBR exponentiation algorithms operate more efficiently than that of BRR. © 1995.
Sun, 01 Oct 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/527441995-10-01T00:00:00Z
- Duadic sequences of prime lengthshttps://scholarbank.nus.edu.sg/handle/10635/38915Title: Duadic sequences of prime lengths
Authors: Ding, C.; Helleseth, T.; Lam, K.Y.
Abstract: Legendre sequences have a number of interesting properties. Their counterparts in coding theory are binary quadratic residue codes. In this paper we study a class of binary sequences, called duadic sequences whose counterparts in coding theory are duadic codes. We calculate their linear complexity, study their autocorrelation and crosscorrelation properties, give exact formulas for the number of bigrams in a cycle, investigate their decimation properties, and discuss their implementation. © 2000 Elsevier Science B.V. All rights reserved.
Sat, 01 Jan 2000 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/389152000-01-01T00:00:00Z
- Several classes of binary sequences with three-level autocorrelationhttps://scholarbank.nus.edu.sg/handle/10635/38910Title: Several classes of binary sequences with three-level autocorrelation
Authors: Ding, C.; Helleseth, T.; Lam, K.Y.
Abstract: In this correspondence we describe several classes of binary sequences with three-level autocorrelation. Those classes of binary sequences are based on cyclic almost difference sets. Some classes of binary sequences have optimum autocorrelation. © 1999 IEEE.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/389101999-01-01T00:00:00Z
- On identification secret sharing schemeshttps://scholarbank.nus.edu.sg/handle/10635/39580Title: On identification secret sharing schemes
Authors: Cai, N.; Lam, K.Y.
Abstract: Let ℘ be a set of participants sharing a secret from a set of secrets. A secret sharing scheme is a protocol such that any qualified subset of ℘ can determine the secret by pooling their shares, the messages which they receive, without error, whereas non-qualified subsets of ℘ cannot obtain any knowledge about the secret when they pool what they receive. In (optimal) schemes, the sizes of shared secrets depend on the sizes of shares given to the participants. Namely the former grow up exponentially as the latter increase exponentially. In this paper, instead of determining the secret, we require the qualified subsets of participants to identify the secret. This change would certainly make no difference from determining secret if no error for identification were allowed. So here we relax the requirement to identification such that an error may occur with a vanishing probability as the sizes of the secrets grow up. Under relaxed condition this changing allows us to share a set of secrets with double exponential size as the sizes of shares received by the participants exponentially grow. Thus much longer secret can be shared. On the other hand, by the continuity of Shannon entropy we have that the relaxation makes no difference for (ordinary) secret sharing schemes. We obtain the characterizations of relations of sizes of secrets and sizes of the shares for identification secret sharing schemes without and with public message. Our idea originates from Ahlswede-Dueck's awarded work in 1989, where the identification codes via channels were introduced. © 2003 Published by Elsevier Science (USA).
Wed, 01 Jan 2003 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/395802003-01-01T00:00:00Z
- Scalable threshold closurehttps://scholarbank.nus.edu.sg/handle/10635/39579Title: Scalable threshold closure
Authors: Zhang, C.; Lam, K.-Y.; Jajodia, S.
Abstract: Secret sharing is an important concept for implementing robust and secure computer systems. A (t, ℓ)-threshold scheme such as Shamir's (Commun. ACM22(11) (1979) 612-613) is a mechanism that allows a set of ℓ participants to share a secret such that only subsets of t or more participants can reconstruct it. The threshold scheme, though simple and easy to implement, is not flexible enough to support complex secret sharing policies typical in practical systems. An access structure (Benaloh and Leichter, Advances in Cryptology - CRYPTO'88, Lecture Notes in Computer Science, vol. 403, Springer, Berlin, 1990, pp. 27-35; Ito et al., Globecom'87, Tokyo, Japan, 1987, pp. 99-102), on the other hand, is a powerful concept by which complex secret sharing schemes may be represented. However, the implementation is very complicated when the access structure contains a great number of authorized sets. This paper introduces a new construction for the secret sharing schemes called threshold closure, which allows a complex access structure it represents to be realized by possibly the fewest number of (t, ℓ)-threshold schemes. © 1999 Elsevier Science B.V. All rights reserved.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/395791999-01-01T00:00:00Z
- Fast square-and-multiply exponentiation for RSAhttps://scholarbank.nus.edu.sg/handle/10635/99287Title: Fast square-and-multiply exponentiation for RSA
Authors: Hui, L.C.K.; Lam, K.-Y.
Abstract: The authors describe a practical technique for improving the performance of square-and-multiply exponentiation. A family of linear time algorithms, denoted by SS(l) where l determines the maximum length of precomputed exponents, is presented. Analysis on n-bit exponents shows that the average number of multiplications required tends to n/(l+1) for large n.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/992871994-01-01T00:00:00Z
- Implementing a highly available network directory servicehttps://scholarbank.nus.edu.sg/handle/10635/99306Title: Implementing a highly available network directory service
Authors: Lam, K.-Y.; Salkield, T.
Abstract: This article presents a new technique for implementing the kind of directory services that frequently occur in the design of network applications conforming to the C.C.I.T.T. X.500 recommendation. A directory service is an important part of a computer network because it implements some logical to physical address translation to allow user and machine mobility in the system. This service has a high availability requirement in that the normal functioning of network applications rely heavily on their ability to locate communicating parties in a flexible and dynamic environment. In this article, a technique for implementing directory services that satisfy this availability requirement is presented. © 1997 by Elsevier Science Inc.
Tue, 01 Apr 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/993061997-04-01T00:00:00Z
- Multivariate data analysis software for enhancing system securityhttps://scholarbank.nus.edu.sg/handle/10635/99344Title: Multivariate data analysis software for enhancing system security
Authors: Lam, K.-Y.; Hui, L.; Chung, S.-L.
Abstract: This article describes an intrusion detection technique that aims to enhance the security of computing systems. The idea of intrusion detection is based on the hypothesis that computer users are typically involved in specific types of activity, and the set of programs they use will normally reflect that activity. Hence, security violations could be detected from abnormal patterns of system usage. Intrusion detection almost invariably involves two components: system monitoring and data analysis. In general, system monitoring records everything that each user performs in the system. Monitoring information is analyzed by use of some data analysis technique to abstract user behavior patterns from the audit log. Although the concept of system monitoring is widely supported in today's computer systems (at least for accounting purposes), the provision of tools for analyzing monitoring information is not sufficient. We present a multivariate data analysis technique that is a nice mathematical tool for the analysis of user behavior patterns in intrusion detection. Our system records all user activities in each login session; abnormal sessions are identified when the monitoring data are analyzed. Data analysis involves two steps: analysis of correlations and classification of behavior patterns. Analysis of correlations, which is based on standardized principal components analysis, partitions the set of user sessions into groups such that sessions within the same group are closely correlated and hence governed by the same behavior pattern. Classification of behavior patterns is automated by a cluster recognition technique. To visualize analysis results, the multivariate data set is summarized by factor analysis. © 1995.
Fri, 01 Dec 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/993441995-12-01T00:00:00Z
- Replay tolerance of authentication protocolshttps://scholarbank.nus.edu.sg/handle/10635/99401Title: Replay tolerance of authentication protocols
Authors: Lam, K.-Y.
Abstract: This research note addresses the problem of message replay in distributed authentication. It discusses the merits and defeats of three most widely accepted approaches to the replay problem. It then presents a different approach which, though difficult to achieve in practice, has been accepted to be most tolerant to replays in distributed systems. This note also describes a practical implementation of this replay-tolerance approach. © 1995.
Fri, 01 Dec 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/994011995-12-01T00:00:00Z
- On the Efficient Implementation of Fair Non-repudiationhttps://scholarbank.nus.edu.sg/handle/10635/99362Title: On the Efficient Implementation of Fair Non-repudiation
Authors: You, C.-H.; Zhou, J.; Lam, K.-Y.
Abstract: Due to the explosive growth of electronic businesses carried on the Internet, non-repudiation services turn out to be increasingly important. Non-repudiation services protect the transacting parties against any false denial that a particular event or action has taken place, in which evidence will be generated, collected and maintained to enable the settlement of disputes. Several fair non-repudiation protocols have been proposed, which support non-repudiation of origin and non-repudiation of receipt while neither the originator nor the recipient can gain an advantage by quitting prematurely or otherwise misbehaving during a transaction. However, a critical issue on how to maintain the validity of non-repudiation evidence efficiently during and after a transaction was not considered. This paper uses the idea of evidence chaining to address such a problem.
Thu, 01 Oct 1998 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/993621998-10-01T00:00:00Z
- Hash function based on block cipherhttps://scholarbank.nus.edu.sg/handle/10635/99303Title: Hash function based on block cipher
Authors: Yi, X.; Lam, K.Y.
Abstract: A new 2m-bit iterated hash function based on an m-bit block cipher with a 2m-bit key is presented. The results of security analysis show that the hash function can be expected to have ideal computational security against the five attacks when the underlying cipher is assumed to have no weakness.
Thu, 06 Nov 1997 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/993031997-11-06T00:00:00Z
- Designing a system infrastructure for distributed programshttps://scholarbank.nus.edu.sg/handle/10635/99239Title: Designing a system infrastructure for distributed programs
Authors: Lam, K.-Y.; Hui, L.C.-K.
Abstract: A distributed program is one that consists of several components distributed over a network of computers. The reliability of a distributed program is strongly affected by the behaviour of the underlying distributed system software platform. One of the most fundamental issues in improving the reliability of distributed programs is to provide a better environment within which these programs operate. This paper investigates the functional requirement of the infrastructure of a distributed operating system in anticipation of the goal of improving the reliability of distributed programs. It identifies the major problems that make the task of achieving high software quality hard to accomplish, then suggests possible functionality that is advisable for the system infrastructure to provide. The design and implementation of the new distributed system service are then described.
Thu, 01 Aug 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/992391996-08-01T00:00:00Z
- Efficiency of SS(l) square-and-multiply exponentiation algorithmshttps://scholarbank.nus.edu.sg/handle/10635/99257Title: Efficiency of SS(l) square-and-multiply exponentiation algorithms
Authors: Lam, K.-Y.; Hui, L.C.K.
Abstract: SS(l) has been demonstrated experimentally to be the fastest square-and-multiply exponentiation scheme based on precomputation and string substitution. The Letter provides a complete proof of the efficiency of the SS(l) algorithm. It shows that SS(l) is a minimum weight representation scheme and proves that the expected weight of an n-bit SS(l)-represented exponent is n/(l+1) for large n.
Thu, 08 Dec 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/992571994-12-08T00:00:00Z
- Efficient nearer-ancestor algorithm for network routinghttps://scholarbank.nus.edu.sg/handle/10635/99260Title: Efficient nearer-ancestor algorithm for network routing
Authors: Lam, K.-Y.; Hui, L.C.K.
Abstract: This research note addresses the problem of efficiently updating routing tables in computer networks. Network routing usually involves the collection of network status information and the execution of routing algorithms based on which routing tables for each network node are created. Nearer-ancestor finding algorithm is an important part of the routing algorithm. Therefore, provisions of efficient nearer-ancestor finding algorithms will help to improve the overall performance of the routing algorithm. This note presents an efficient and practical solution for finding nearer-ancestors.
Tue, 01 Oct 1996 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/992601996-10-01T00:00:00Z