ID-based Ring Signature and Proxy Ring Signature Schemes from Bilinear Pairings

In 2001, Rivest et al. firstly introduced the concept of ring signatures. A ring signature is a simplified group signature without any manager. It protects the anonymity of a signer. The first scheme proposed by Rivest et al. was based on RSA cryptosystem and certificate based public key setting. The first ring signature scheme based on DLP was proposed by Abe, Ohkubo, and Suzuki. Their scheme is also based on the general certificate-based public key setting too. In 2002, Zhang and Kim proposed a new ID-based ring signature scheme using pairings. Later Lin and Wu proposed a more efficient ID-based ring signature scheme. Both these schemes have some inconsistency in computational aspect. In this paper we propose a new ID-based ring signature scheme and a proxy ring signature scheme. Both the schemes are more efficient than existing one. These schemes also take care of the inconsistencies in above two schemes.Comment: Published with ePrint Archiv

Authentication Protocols and Privacy Protection

Tato dizertační práce se zabývá kryptografickými prostředky pro autentizaci. Hlavním tématem však nejsou klasické autentizační protokoly, které nabízejí pouze ověření identity, ale tzv. atributové autentizační systémy, pomocí kterých mohou uživatelé prokazovat svoje osobní atributy. Tyto atributy pak mohou představovat jakékoliv osobní informace, např. věk, národnost či místo narození. Atributy mohou být prokazovány anonymně a s podporou mnoha funkcí na ochranu digitální identity. Mezi takové funkce patří např. nespojitelnost autentizačních relací, nesledovatelnost, možnost výběru prokazovaných atributů či efektivní revokace. Atributové autentizační systémy jsou již nyní považovány za nástupce současných systémů v oficiálních strategických plánech USA (NSTIC) či EU (ENISA). Část požadovaných funkcí je již podporována existujícími kryptografickými koncepty jako jsou U-Prove či idemix. V současné době však není známý systém, který by poskytoval všechny potřebné funkce na ochranu digitální identity a zároveň byl prakticky implementovatelný na zařízeních, jako jsou čipové karty. Mezi klíčové slabiny současných systémů patří především chybějící nespojitelnost relací a absence revokace. Není tak možné efektivně zneplatnit zaniklé uživatele, ztracené či ukradené autentizační karty či karty škodlivých uživatelů. Z těchto důvodů je v této práci navrženo kryptografické schéma, které řeší slabiny nalezené při analýze existujících řešení. Výsledné schéma, jehož návrh je založen na ověřených primitivech, jako jsou $\Sigma$-protokoly pro důkazy znalostí, kryptografické závazky či ověřitelné šifrování, pak podporuje všechny požadované vlastnosti pro ochranu soukromí a digitální identity. Zároveň je však návrh snadno implementovatelný v prostředí smart-karet. Tato práce obsahuje plný kryptografický návrh systému, formální ověření klíčových vlastností, matematický model schématu v programu Mathematica pro ověření funkčnosti a výsledky experimentální implementace v prostředí .NET smart-karet. I přesto, že navrhovaný systém obsahuje podporu všech funkcí na ochranu soukromí, včetně těch, které chybí u existujících systémů, jeho výpočetní složitost zůstává stejná či nižší, doba ověření uživatele je tedy kratší než u existujících systémů. Výsledkem je schéma, které může velmi znatelně zvýšit ochranu soukromí uživatelů při jejich ověřování, především při využití v elektronických dokladech, přístupových systémech či Internetových službách.This dissertation thesis deals with the cryptographic constructions for user authentication. Rather than classical authentication protocols which allow only the identity verification, the attribute authentication systems are the main topic of this thesis. The attribute authentication systems allow users to give proofs about the possession of personal attributes. These attributes can represent any personal information, for example age, nationality or birthplace. The attribute ownership can be proven anonymously and with the support of many features for digital identity protection. These features include, e.g., the unlinkability of verification sessions, untraceability, selective disclosure of attributes or efficient revocation. Currently, the attribute authentication systems are considered to be the successors of existing authentication systems by the official strategies of USA (NSTIC) and EU (ENISA). The necessary features are partially provided by existing cryptographic concepts like U-Prove and idemix. But at this moment, there is no system providing all privacy-enhancing features which is implementable on computationally restricted devices like smart-cards. Among all weaknesses of existing systems, the missing unlinkability of verification sessions and the absence of practical revocation are the most critical ones. Without these features, it is currently impossible to invalidate expired users, lost or stolen authentication cards and cards of malicious users. Therefore, a new cryptographic scheme is proposed in this thesis to fix the weaknesses of existing schemes. The resulting scheme, which is based on established primitives like $\Sigma$-protocols for proofs of knowledge, cryptographic commitments and verifiable encryption, supports all privacy-enhancing features. At the same time, the scheme is easily implementable on smart-cards. This thesis includes the full cryptographic specification, the formal verification of key properties, the mathematical model for functional verification in Mathematica software and the experimental implementation on .NET smart-cards. Although the scheme supports all privacy-enhancing features which are missing in related work, the computational complexity is the same or lower, thus the time of verification is shorter than in existing systems. With all these features and properties, the resulting scheme can significantly improve the privacy of users during their verification, especially when used in electronic ID systems, access systems or Internet services.

Certificateless Designated Verifier Proxy Signature

Proxy signature (PS) is a kind of digital signature, in which an entity called original signer can delegate his signing rights to another entity called proxy signer. Designated verifier signature (DVS) is a kind of digital signature where the authenticity of any signature can be verified by only one verifier who is designated by the signer when generating it. Designated verifier proxy signature (DVPS) combines the idea of DVS with the concept of proxy signature (PS) and is suitable for being applied in many scenarios from e-tender, e-voting, e-auction, e-health and e-commerce, etc. Many DVPS schemes have been proposed and Identity-based DVPS (IBDVPS) schemes have also been discussed. Certificateless public-key cryptography (CL-PKC) is acknowledged as an appealing paradigm because there exists neither the certificate management issue as in traditional PKI nor private key escrow problem as in Identity-based setting. A number of certificateless designated verifier signature (CLDVS) schemes and many certificateless proxy signature (CLPS) schemes have been proposed. However, to the best of our knowledge, the concept of Certificateless Designated Verifier Proxy Signature (CLDVPS) has not been appeared in the literature. In this paper, we formalize the definition and the security model of CLDVPS schemes. We then construct the first CLDVPS scheme and prove its security

Strong proxy signature scheme with proxy signer privacy protection.

by Shum Kwan.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 30-32).Abstracts in English and Chinese.Acknowledgement --- p.iiAbstract --- p.iii□ □ --- p.ivChapter 1 . --- Introduction --- p.1Chapter 1.1 --- Introduction to topic --- p.1Chapter 1.2 --- What is proxy signature? --- p.2Chapter 1.3 --- Terminologies in proxy signature --- p.2Chapter 1.4 --- Levels of delegation --- p.3Chapter 1.5 --- Previous work on Proxy Signature --- p.4Chapter 1.6 --- Our Contributions --- p.4Chapter 1.7 --- Thesis Organization --- p.4Chapter 2. --- Backgroun d --- p.6Chapter 2.1 --- Digital Signature --- p.6Chapter 2.2 --- Digital Certificate and CA --- p.6Chapter 2.3 --- Hash Functions --- p.7Chapter 2.4 --- Bit commitment --- p.7Chapter 3. --- Brief introduction to Our Result --- p.8Chapter 3.1 --- A Proxy Signature Scheme with Proxy Signer Privacy Protection --- p.8Chapter 3.2 --- Applications of Proxy Signature --- p.9Chapter 4. --- Detail Explanation of Certified Alias and its Application on Proxy Signature --- p.10Chapter 4.1 --- Introduction --- p.10Chapter 4.2 --- Protecting Signer Privacy Using Certified Alias Definition 4.2.3 --- p.10Chapter 4.3 --- Constructing Proxy signature Scheme by Consecutive Execution of Cryptographic Primitives (Scheme CE) --- p.11Chapter 4.4 --- Constructing Proxy signature Scheme by Direct Form Equations (Scheme DF) --- p.15Chapter 4.5 --- Comparison between scheme CE and scheme DF --- p.19Chapter 4.6 --- Chapter Summary --- p.20Chapter 5 . --- Applications of Proxy Signature with Proxy Signer Privacy Protection --- p.21Chapter 5.1 --- Secure Mobile agent Signature with Itinerary Privacy --- p.21Chapter 5.1.1 --- Introduction to Mobile Agent --- p.21Chapter 5.1.2 --- "Review on Lee, et al. strong non-designated proxy signature scheme for mobile agents" --- p.21Chapter 5.1.3 --- Constructing Signature scheme for Mobile Agent using Proxy signature with Proxy Signer Privacy Protection --- p.22Chapter 5.1.4 --- Remarks --- p.23Chapter 5.2 --- Group Signature with Unlimited Group Size --- p.24Chapter 5.2.1 --- Introduction to group signature --- p.24Chapter 5.2.2 --- Constructing group signature scheme using certified alias --- p.24Chapter 5.2.4 --- Remarks --- p.26Chapter 5.3 --- Chapter Summary --- p.27Chapter 6. --- Conclusions --- p.28Appendix: Paper derived from this thesis --- p.29Bibliography --- p.3

How to win the clonewars: efficient periodic n-times anonymous authentication

We create a credential system that lets a user anonymously authenticate at most n times in a single time period. A user withdraws a dispenser of n e-tokens. She shows an e-token to a verifier to authenticate herself; each e-token can be used only once, however, the dispenser automatically refreshes every time period. The only prior solution to this problem, due to Damg˚ard et al. [30], uses protocols that are a factor of k slower for the user and verifier, where k is the security parameter. Damg˚ard et al. also only support one authentication per time period, while we support n. Because our construction is based on e-cash, we can use existing techniques to identify a cheating user, trace all of her e-tokens, and revoke her dispensers. We also offer a new anonymity service: glitch protection for basically honest users who (occasionally) reuse etokens. The verifier can always recognize a reused e-token; however, we preserve the anonymity of users who do not reuse e-tokens too often.

Aggregatable Certificateless Designated Verifier Signature

In recent years, the Internet of Things (IoT) devices have become increasingly deployed in many industries and generated a large amount of data that needs to be processed in a timely and efficient manner. Using aggregate signatures, it provides a secure and efficient way to handle large numbers of digital signatures with the same message. Recently, the privacy issue has been concerned about the topic of data sharing on the cloud. To provide the integrity, authenticity, authority, and privacy on the data sharing in the cloud storage, the notion of an aggregatable certificateless designated verifier signature scheme (ACLDVS) was proposed. ACLDVS also is a perfect tool to enable efficient privacy-preserving authentication systems for IoT and or the vehicular ad hoc networks (VANET). Our concrete scheme was proved to be secured underling of the Computational Diffie-Hellman assumption. Compared to other related schemes, our scheme is efficient, and the signature size is considerably short

APEX2S: A Two-Layer Machine Learning Model for Discovery of host-pathogen protein-protein Interactions on Cloud-based Multiomics Data

Presented by the avalanche of biological interactions data, computational biology is now facing greater challenges on big data analysis and solicits more studies to mine and integrate cloud-based multiomics data, especially when the data are related to infectious diseases. Meanwhile, machine learning techniques have recently succeeded in different computational biology tasks. In this article, we have calibrated the focus for host-pathogen protein-protein interactions study, aiming to apply the machine learning techniques for learning the interactions data and making predictions. A comprehensive and practical workflow to harness different cloud-based multiomics data is discussed. In particular, a novel two-layer machine learning model, namely APEX2S, is proposed for discovery of the protein-protein interactions data. The results show that our model can better learn and predict from the accumulated host-pathogen protein-protein interactions