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41
Computational bounds on hierarchical data processing with applications to information security
 In Proc. Int. Colloquium on Automata, Languages and Programming (ICALP), volume 3580 of LNCS
, 2005
"... Motivated by the study of algorithmic problems in the domain of information security, in this paper, we study the complexity of a new class of computations over a collection of values associated with a set of n elements. We introduce hierarchical data processing (HDP) problems which involve the comp ..."
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Motivated by the study of algorithmic problems in the domain of information security, in this paper, we study the complexity of a new class of computations over a collection of values associated with a set of n elements. We introduce hierarchical data processing (HDP) problems which involve the computation of a collection of output values from an input set of n elements, where the entire computation is fully described by a directed acyclic graph (DAG). That is, individual computations are performed and intermediate values are processed according to the hierarchy induced by the DAG. We present an Ω(log n) lower bound on various computational cost measures for HDP problems. Essential in our study is an analogy that we draw between the complexities of any HDP problem of size n and searching by comparison in an order set of n elements, which shows an interesting connection between the two problems. In view of the logarithmic lower bounds, we also develop a new randomized DAG scheme for HDP problems that provides close to optimal performance and achieves cost measures with constant factors of the (logarithmic) leading asymptotic term that are close to optimal. Our lower bounds are general, apply to all HDP problems and, along with our new DAG construction, they provide an interesting –as well as useful in the area of algorithm analysis – theoretical framework. We apply our results to two information security problems, data authentication through cryptographic hashing and multicast key distribution using keygraphs and get a unified analysis and treatment for these problems. We show that both problems involve HDP and prove logarithmic lower bounds on their computational and communication costs. In particular, using our new DAG scheme, we present a new efficient authenticated dictionary with improved authentication overhead over previously known schemes. Moreover, through the relation between HDP and searching by comparison, we present a new skiplist version where the expected number of comparisons in a search is 1.25log 2 n + O(1). 1
Indexing Information for Data Forensics
, 2005
"... We introduce novel techniques for organizing the indexing structures of how data is stored so that alterations from an original version can be detected and the changed values specifically identified. We give forensic constructions for several fundamental data structures, including arrays, linked li ..."
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Cited by 23 (5 self)
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We introduce novel techniques for organizing the indexing structures of how data is stored so that alterations from an original version can be detected and the changed values specifically identified. We give forensic constructions for several fundamental data structures, including arrays, linked lists, binary search trees, skip lists, and hash tables. Some of our constructions are based on a new reducedrandomness construction for nonadaptive combinatorial group testing.
Cryptanalysis of video encryption algorithms
 In Proceedings of The 3rd Central European Conference on Cryptology (TATRACRYPT ’03
, 2003
"... Content security is an important issue in multimedia applications. In this paper we perform a cryptanalysis of several encryption algorithms that have been proposed to protect the privacy of MPEG video streams. In particular, we analyze the encryption based on permuting the Huffman codeword list, an ..."
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Content security is an important issue in multimedia applications. In this paper we perform a cryptanalysis of several encryption algorithms that have been proposed to protect the privacy of MPEG video streams. In particular, we analyze the encryption based on permuting the Huffman codeword list, and two selective encryption algorithms VEA and MVEA. For the convenience of the reader, we provide a simple overview of MPEG encoding, and we include all analyzed algorithms and their characteristics.
A Secure Identification and Key agreement protocol with user Anonymity (SIKA)
"... user identification, authentication, key agreement, anonymity, RSA, DenialofService (DoS) attack Anonymity is a desirable security feature in addition to providing user identification and key agreement during a user’s login process. Recently, Yang et al., proposed an efficient user identification ..."
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user identification, authentication, key agreement, anonymity, RSA, DenialofService (DoS) attack Anonymity is a desirable security feature in addition to providing user identification and key agreement during a user’s login process. Recently, Yang et al., proposed an efficient user identification and key distribution protocol while preserving user anonymity. Their protocol addresses a weakness in the protocol proposed by Wu and Hsu. Unfortunately, Yang’s protocol poses a vulnerability that can be exploited to launch a DenialofService (DoS) attack. In this paper, we cryptanalyze Yang’s protocol and present the DoS attack. We further secure their protocol by proposing a Secure Identification and Key agreement protocol with user Anonymity (SIKA) that overcomes the above limitation while achieving security features like identification, authentication, key agreement and user anonymity.
Multicollision Attacks on a Class of Hash Functions
 IACR PREPRINT ARCHIVE
, 2005
"... In a recent paper, A. Joux [7] showed multicollision attacks on the classical iterated hash function. (A multicollision is a set of inputs whose hash values are same.) He also showed how the multicollision attacks can be used to get a collision attack on the concatenated hash function. In this paper ..."
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Cited by 7 (0 self)
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In a recent paper, A. Joux [7] showed multicollision attacks on the classical iterated hash function. (A multicollision is a set of inputs whose hash values are same.) He also showed how the multicollision attacks can be used to get a collision attack on the concatenated hash function. In this paper, we first try to fix the attack by introducing a natural and wide class hash functions. However, we show that the multicollision attacks also exist in this general class. Thus, we rule out a natural and a wide class of hash functions as candidates for multicollision secure hash functions.
B.: Cryptography using Chebyshev polynomials
 Laurier University, Waterloo
, 2004
"... We consider replacing the monomial xn with the Chebyshev polynomial Tn(x) in the DiffieHellman and RSA cryptography algorithms. We show that we can generalize the binary powering algorithm to compute Chebyshev polynomials, and that the inverse problem of computing the degree n, the discrete log ..."
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We consider replacing the monomial xn with the Chebyshev polynomial Tn(x) in the DiffieHellman and RSA cryptography algorithms. We show that we can generalize the binary powering algorithm to compute Chebyshev polynomials, and that the inverse problem of computing the degree n, the discrete log problem for Tn(x) mod p, is as difficult as that for xn mod p. 1
A Novel Blind Signature Scheme based on NybergRueppel Signature Scheme and Applying
 in Offline Digital Cash. In 10th IEEE International Conference on Information Technology, (ICIT 2007
, 2007
"... In this paper, a novel Blind Signature Scheme (BSS) based on NybergRueppel Signature Scheme (NRSS) using Elliptic Curve Discrete Logarithm Problem (ECDLP) has been proposed. Blind signature allows a requester to obtain signature from a signer on any document, in such a way that the authority learns ..."
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In this paper, a novel Blind Signature Scheme (BSS) based on NybergRueppel Signature Scheme (NRSS) using Elliptic Curve Discrete Logarithm Problem (ECDLP) has been proposed. Blind signature allows a requester to obtain signature from a signer on any document, in such a way that the authority learns nothing about the message that is being signed. Blind Signatures are useful in protocols that guarantee the anonymity of the participants. As an instance, the application of the scheme in off line digital cash has been described. The proposed scheme can be easily extended to Evoting and others applications where the requester needs a blind signature on the message.
On ServerAided Computation for RSA Protocols with Private Key Splitting
, 2003
"... Serveraided secret computation is a widely investigated topic due to the obvious benefits of such an approach in applications where small constrained terminal equipment is used. Recently, also other ways of using servers to improve the security functionality of end user devices have been proposed. ..."
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Serveraided secret computation is a widely investigated topic due to the obvious benefits of such an approach in applications where small constrained terminal equipment is used. Recently, also other ways of using servers to improve the security functionality of end user devices have been proposed. By splitting the private computation functionality between the server and the client, end user devices can be protected from being misused if captured, or the usage of the private key can be controlled. In this contribution the problem of combining different security tasks delegated to the servers by client devices is investigated. The capture resilience and delegated authorisation protocols based on RSA is achieved by composition of the private key as a sum of two partial keys. To reduce the computation of one party, its partial key must be reduced. Previously, continuous fractions were used to break RSA with a short private key. We apply this method to the case where the private RSA key itself is large but it is split into two parts, one of which is small. Our results show that for some typical parameter values the party who knows the longer part of the private key can easily recover the small part. Key words: E and Mbusiness security, serveraided secure computation, captureresilience, delegated authorisation, RSA system, small RSA exponents 1
Toward usable, robust memometric authentication: An evaluation of selected password generation assistance
 Florida State University
"... This Dissertation Open Access is brought to you for free and open access by the The Graduate School at DigiNole Commons. It has been accepted for inclusion in Electronic Theses, Treatises and Dissertations by an authorized administrator of DigiNole Commons. For more information, please contact ..."
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This Dissertation Open Access is brought to you for free and open access by the The Graduate School at DigiNole Commons. It has been accepted for inclusion in Electronic Theses, Treatises and Dissertations by an authorized administrator of DigiNole Commons. For more information, please contact
777—793 Transactions
 on Software Engineering
, 1996
"... Feng, who have raised me to be the person I am today. Thank you for all the unconditional love, guidance, and support that you have always given me. iii The evolution of wireless networks and mobile device technologies has increased concerns about performance and security of mobile systems. We propo ..."
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Feng, who have raised me to be the person I am today. Thank you for all the unconditional love, guidance, and support that you have always given me. iii The evolution of wireless networks and mobile device technologies has increased concerns about performance and security of mobile systems. We propose a new secured applicationlevel architecture for a twoparty mobile payment transaction that is carried out between a resourcelimited mobile device and a resourcerich computer server over wireless networks. As an example of such transactions, the mobile banking transaction is focused on throughout this thesis. The proposed architecture, namely SA2pMP, employs a lightweight cryptography scheme (combining both a Publickey cryptography algorithm (ECDSA) and a Symmetrickey cryptography algorithm (AES)), a multifactor authentication mechanism, and a transaction log strategy. The proposed architecture is designed to satisfy the four properties of confidentiality, authentication, integrity and nonrepudiation that are required by any secure system. The architecture can be implemented on a Java ME enabled mobile