Dark signalling and code division multiple access in an optical fibre LAN with a bus topology

This thesis describes an optical fibre network that uses a bus topology and Code Division Multiple Access (CDMA). Various potential configurations are analysed and compared and it is shown that a serious limitation of optical CDMA schemes using incoherent correlators is the effect of optical beating due to the presence of multiple incoherent optical signals at the receiver photodiode. The network proposed and analysed in this thesis avoids beating between multiple optical fields because it only uses a single, shared, optical source. It does this through the SLIM (Single Light-source with In-line Modulation) configuration in which there is a continuously-operating light source at the head-end of a folded bus, and modulators at the nodes to impose signals on the optical field in the form of pulses of darkness which propagate along the otherwise continuously bright bus. Optical CDMA can use optical-fibre delay-line correlators as matched filters, and these may be operated either coherently or incoherently.Coherent operation is significantly more complex than incoherent operation, but incoherent correlators introduce further beating even in a SLIM network. A new design of optical delay-line correlator, the hybrid correlator, is therefore proposed, analysed and demonstrated. It is shown to eliminate beating. A model of a complete network predicts that a SLIMbus using optical CDMA with hybrid correlators can be operated at TeraBaud rates with the number of simultaneous users limited by multiple access interference (MAI), determined only by the combinatorics of the code set

Communication Security in Wireless Sensor Networks

A wireless sensor network (WSN) usually consists of a large number of small, low-cost devices that have limited energy supply, computation, memory, and communication capacities. Recently, WSNs have drawn a lot of attention due to their broad applications in both military and civilian domains. Communication security is essential to the success of WSN applications, especially for those mission-critical applications working in unattended and even hostile environments. However, providing satisfactory security protection in WSNs has ever been a challenging task due to various network & resource constraints and malicious attacks. This motivates the research on communication security for WSNs. This dissertation studies communication security in WSNs with respect to three important aspects. The first study addresses broadcast/multicast security in WSNs. We propose a multi-user broadcast authentication technique, which overcomes the security vulnerability of existing solutions. The proposed scheme guarantees immediate broadcast authentication by employing public key cryptography, and achieves the efficiency through integrating various techniques from different domains. We also address multicast encryption to solve data confidentiality concern for secure multicast. We propose an efficient multicast key management scheme supporting a wide range of multicast semantics, which utilizes the fact that sensors are both routers and end-receivers. The second study addresses data report security in WSNs. We propose a location-aware end-to-end security framework for WSNs, in which secret keys are bound to geographic locations so that the impact of sensor compromise are limited only to their vicinity. The proposed scheme effectively defeats not only bogus data injection attacks but also various DoS attacks. In this study, we also address event boundary detection as a specific case of secure data aggregation in WSNs. We propose a secure and fault-tolerant event boundary detection scheme, which securely detects the boundaries of large spatial events in a localized statistic manner. The third study addresses random key pre-distribution in WSNs. We propose a keyed-hash-chain-based key pool generation technique, which leads to a more efficient key pre-distribution scheme with better security resilience in the case of sensor compromise

Threshold Ring Signatures: New Definitions and Post-Quantum Security

A $t$-out-of-$N$ threshold ring signature allows $t$ parties to jointly and anonymously compute a signature on behalf on $N$ public keys, selected in an arbitrary manner among the set of all public keys registered in the system. Existing definitions for $t$-out-of-$N$ threshold ring signatures guarantee security only when the public keys are honestly generated, and many even restrict the ability of the adversary to actively participate in the computation of the signatures. Such definitions do not capture the open settings envisioned for threshold ring signatures, where parties can independently add themselves to the system, and join other parties for the computation of the signature. Furthermore, known constructions of threshold ring signatures are not provably secure in the post-quantum setting, either because they are based on non-post quantum secure problems (e.g. Discrete Log, RSA), or because they rely on transformations such as Fiat-Shamir, that are not always secure in the quantum random oracle model (QROM). In this paper, we provide the first definition of $t$-out-of-$N$ threshold ring signatures against {\em active} adversaries who can participate in the system and arbitrarily deviate from the prescribed procedures. Second, we present a post-quantum secure realization based on {\em any} (post-quantum secure) trapdoor commitment, which we prove secure in the QROM. Our construction is black-box and it can be instantiated with any trapdoor commitment, thus allowing the use of a variety of hardness assumptions

Cryptography in privacy-preserving applications.

Tsang Pak Kong.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 95-107).Abstracts in English and Chinese.Abstract --- p.iiAcknowledgement --- p.ivChapter 1 --- Introduction --- p.1Chapter 1.1 --- Privacy --- p.1Chapter 1.2 --- Cryptography --- p.5Chapter 1.2.1 --- History of Cryptography --- p.5Chapter 1.2.2 --- Cryptography Today --- p.6Chapter 1.2.3 --- Cryptography For Privacy --- p.7Chapter 1.3 --- Thesis Organization --- p.8Chapter 2 --- Background --- p.10Chapter 2.1 --- Notations --- p.10Chapter 2.2 --- Complexity Theory --- p.11Chapter 2.2.1 --- Order Notation --- p.11Chapter 2.2.2 --- Algorithms and Protocols --- p.11Chapter 2.2.3 --- Relations and Languages --- p.13Chapter 2.3 --- Algebra and Number Theory --- p.14Chapter 2.3.1 --- Groups --- p.14Chapter 2.3.2 --- Intractable Problems --- p.16Chapter 2.4 --- Cryptographic Primitives --- p.18Chapter 2.4.1 --- Public-Key Encryption --- p.18Chapter 2.4.2 --- Identification Protocols --- p.21Chapter 2.4.3 --- Digital Signatures --- p.22Chapter 2.4.4 --- Hash Functions --- p.24Chapter 2.4.5 --- Zero-Knowledge Proof of Knowledge --- p.26Chapter 2.4.6 --- Accumulators --- p.32Chapter 2.4.7 --- Public Key Infrastructure --- p.34Chapter 2.5 --- Zero Knowledge Proof of Knowledge Protocols in Groups of Unknown Order --- p.36Chapter 2.5.1 --- The Algebraic Setting --- p.36Chapter 2.5.2 --- Proving the Knowledge of Several Discrete Logarithms . --- p.37Chapter 2.5.3 --- Proving the Knowledge of a Representation --- p.38Chapter 2.5.4 --- Proving the Knowledge of d Out of n Equalities of Discrete Logarithms --- p.39Chapter 2.6 --- Conclusion --- p.42Chapter 3 --- Related Works --- p.43Chapter 3.1 --- Introduction --- p.43Chapter 3.2 --- Group-Oriented Signatures without Spontaneity and/or Anonymity --- p.44Chapter 3.3 --- SAG Signatures --- p.46Chapter 3.4 --- Conclusion --- p.49Chapter 4 --- Linkable Ring Signatures --- p.50Chapter 4.1 --- Introduction --- p.50Chapter 4.2 --- New Notions --- p.52Chapter 4.2.1 --- Accusatory Linking --- p.52Chapter 4.2.2 --- Non-slanderability --- p.53Chapter 4.2.3 --- Linkability in Threshold Ring Signatures --- p.54Chapter 4.2.4 --- Event-Oriented Linking --- p.55Chapter 4.3 --- Security Model --- p.56Chapter 4.3.1 --- Syntax --- p.56Chapter 4.3.2 --- Notions of Security --- p.58Chapter 4.4 --- Conclusion --- p.63Chapter 5 --- Short Linkable Ring Signatures --- p.64Chapter 5.1 --- Introduction --- p.64Chapter 5.2 --- The Construction --- p.65Chapter 5.3 --- Security Analysis --- p.68Chapter 5.3.1 --- Security Theorems --- p.68Chapter 5.3.2 --- Proofs --- p.68Chapter 5.4 --- Discussion --- p.70Chapter 5.5 --- Conclusion --- p.71Chapter 6 --- Separable Linkable Threshold Ring Signatures --- p.72Chapter 6.1 --- Introduction --- p.72Chapter 6.2 --- The Construction --- p.74Chapter 6.3 --- Security Analysis --- p.76Chapter 6.3.1 --- Security Theorems --- p.76Chapter 6.3.2 --- Proofs --- p.77Chapter 6.4 --- Discussion --- p.79Chapter 6.5 --- Conclusion --- p.80Chapter 7 --- Applications --- p.82Chapter 7.1 --- Offline Anonymous Electronic Cash --- p.83Chapter 7.1.1 --- Introduction --- p.83Chapter 7.1.2 --- Construction --- p.84Chapter 7.2 --- Electronic Voting --- p.85Chapter 7.2.1 --- Introduction --- p.85Chapter 7.2.2 --- Construction . --- p.87Chapter 7.2.3 --- Discussions --- p.88Chapter 7.3 --- Anonymous Attestation --- p.89Chapter 7.3.1 --- Introduction --- p.89Chapter 7.3.2 --- Construction --- p.90Chapter 7.4 --- Conclusion --- p.91Chapter 8 --- Conclusion --- p.92A Paper Derivation --- p.94Bibliography --- p.9

A Provably Secure Short Signature Scheme from Coding Theory

Signatures with partially message recovery in which some parts of messages are not transmitted with signatures to make them shorter are useful where bandwidth is one of the crucial concern and especially in case of signing short messages in applications such as time stamping, certified email services and identitybased cryptosystems. In this paper, to have quantum-attackresistant short signatures, a signature scheme with partially message recovery from coding theory is proposed. The security of the proposed scheme is proved under Goppa Parametrized Bounded Decoding and the Goppa Code Distinguishing assumptions in the random oracle model. Relying on the partially message recovery property, the proposal is shorter than the Dallot signature scheme, the only provably secure and practical code-based signature scheme. We should highlight that our scheme can be used as a building block of code-based signature schemes with additional properties since it compared to Dallot signature scheme not only improves its communication overhead but also it preserves its signature efficiency

A Provably Secure Code-based Concurrent Signature Scheme

Concurrent signatures allow two entities to generate two signatures in such a way that both signatures are ambiguous till some information is revealed by one of the parties. This kind of signature is useful in auction protocols and a wide range of scenarios in which involving participants are mutually distrustful. In this paper, to have quantum-attack-resistant concurrent signatures as recommended by National Institute of Standards and Technology (NISTIR 8105), the first concurrent signature scheme based on coding theory is proposed. Then, its security is proved under Goppa Parameterized Bounded Decoding and the Goppa Code Distinguishing assumptions in the random oracle model. We should highlight that our proposal can be a post-quantum candidate for fair exchange of signatures without a trusted third party in an efficient way (without a highly degree of interactions)