Cloud computing provides a novel computing paradigm for enterprises to store programs and data in the Cloud in a transparent manner, which poses the challenge of security and privacy. In this paper, based on homomorphic cryptography and Zero-Knowledge Proof, we present a novel privacy-preserving scheme for Cloud publish/subscribe service, which achieve efficient privacy-preserving authentication, data integrity, and publish-subscribe confidentiality. The performance evaluation and security analysis demonstrate the practice and validity of the proposed scheme.
The main idea is to protect the signer of a document against the document being digitally distributed without the cooperation of signer. This paper proposes a new scheme of undeniable signature, which is so effective and improved D. Chaum's scheme. And our scheme which is zero-knowledge proved by using one-way function and partition - selection method, shows that its communication(challenge-response) only needs much fewer times during the confirmation protocol and disavowal protocol respectively, being very useful for wireless network environment. In the meantime our scheme allows the verifier to verify that the signature is valid, while the signer doesn't know the original message and the signature, to preserve the privacy of the verifier.
Commitment schemes, secret sharing schemes, interactive zero-knowledge proofs which underlie the offered interactive secrete sharing schemes are considered. Such schemes are one of the main computing primitives in the theory of secure computations. Base elements of the theory of secure computations and schemes of construction of synchronous verifiable secrete sharing as schemes of secure function evaluation are resulted.
A sensor network typically refers to a collection of sensor nodes equipped with sensing, communication and processing capabilities. It brings an opportunity to solve many difficult problems including real time monitoring, tracking, and controlling. While the applications of sensor networking become many and varied, security has always been one of the major concerns in real deployments. In this dissertation, we design physical primitives for secure communication in wireless sensor networks, and develop a wireless security framework to provide conventional security services. We investigate the feasibility of achieving perfect secrecy and information authenticity without shared secrets via two physical primitives: (i) cooperative jamming primitive, where we introduce a secure coding problem in which not only the sender but also the receiver participates in the coding. In essence, the receiverâs role is to selectively jam the senderâs transmission at the level of bits, bytes, or packets. We then design a class of secure codes, called âdialog codesâ, for diverse channel models and receiver models. (ii) spatial verification primitive, where we exploit the spatial signature induced by the radio communications of a node on its neighboring nodes, and design a spatial primitive that robustly and efficiently validates the authenticity of the source of messages. To address trust initialization, we propose a zero knowledge proof alternative that allows bootstrapping trust among individuals in a distributed way.
Matteo Maffei, Giulio Malavolta, Manuel Reinert, Dominique Schröder
The existing (election) voting systems, e.g., representative democracy, have many limitations and often fail to serve the best interest of the people in collective decision making. To address this issue, the concept of liquid democracy has been emerging as an alternative decision-making model to make better use of "the wisdom of crowds". Very recently, a few liquid democracy implementations, e.g. Google Votes and Decentralized Autonomous Organization (DAO), are released; however, those systems only focus on the functionality aspect, as no privacy/anonymity is considered. In this work, we, for the first time, provide a rigorous study of liquid democracy under the Universal Composability (UC) frame- work. In the literature, liquid democracy was achieved via two separate stages -- delegation and voting. We propose an efficient liquid democracy e-voting scheme that uni es these two stages. At the core of our design is a new voting concept called statement voting, which can be viewed as a natural extension of the conventional voting approaches. We remark that our statement voting can be extended to enable more complex voting and generic ledger-based non-interactive multi-party computation. We believe that the statement voting concept opens a door for constructing a new class of e-voting schemes.
Zero-knowledge proofs have a vast applicability in the domain of cryptography, stemming from the fact that they can be used to force potentially malicious parties to abide by the rules of a protocol, without forcing them to reveal their secrets. ÎŁ-protocols are a class of zero-knowledge proofs that can be implemented efficiently and that suffice for a great variety of practical applications. This paper presents a first machine-checked formalization of a comprehensive theory of ÎŁ-protocols. The development includes basic definitions, relations between different security properties that appear in the literature, and general composability theorems. We show its usefulness by formalizingâand proving the securityâof concrete instances of several well-known protocols. The formalization builds on CertiCrypt, a framework that provides support to reason about cryptographic systems in the Coq proof assistant, and that has been previously used to formalize security proofs of encryption and signature schemes.
Ein E- Voting System muss einerseits sicher sein andererseits muss es gewĂ€hrleisten dass jede Wahl berĂŒcksichtigt und anonym ausgewertet wird. \nDieses Projekt befasst sich mit der Aufgabe, ein solch sicheres, stabiles und transparentes Wahlsystem anzubieten. Das Ziel der Arbeit ist es, einen Web Client zu entwickeln, der mit Hilfe einer Big- Integer Library und JavaScript Funktionen das fĂŒr E- Voting geeignete DamgĂ„rd- Jurik Kryptosystem zu implementiert. Weiter galt es, die VerfĂŒgbarkeit von echten Zufallszahlen in JavaScript abzuklĂ€ren. Die generierten DatensĂ€tze sind in der JavaScript Object Notation (JSON) an den Server weiterzuleiten. In einem optionalen Teil der Arbeit sollte die Wohlgeformtheit der verschlĂŒsselten Stimmzettel mittels eines Zero-Knowledge Proofs Protokoll nachgewiesen werden können. \nDer verwendete asymmetrische DamgĂ„rd- Jurik VerschlĂŒsselungsalgorithmus, hat die homomorphe Eigenschaft, dass die Multiplikation chiffrierter Werte gleich der verschlĂŒsselten Summe der entsprechenden Klartexte entspricht. Da nur das aufkumulierte Schlussresultat der Abstimmung entschlĂŒsselt wird, ist dadurch die AnonymitĂ€t der einzelnen Stimmen gewĂ€hrleistet. Um die GĂŒltigkeit eines verschlĂŒsselten Wahlzettels zu ĂŒberprĂŒfen, wird ein Zero-Knowledge Proofs Protokoll verwendet. Da JavaScript nur mit Zahlen bis 53 Bit rechnen kann, ist fĂŒr die Berechnungen eine JavaScript Big- Integer Library notwendig. Es wurden verschiedene Bibliotheken getestet und im Detail ausgewertet. Ebenfalls wurde die Möglichkeit echte Zufallszahlen plattformunabhĂ€ngig zu generieren abgeklĂ€rt. \nDie Wahl der Big-Integer Library ist auf jsbn.js der Stanford University gefallen und fĂŒr die Generierung von Zufallszahlen auf jscrypto.js, welche durch die Auswertung von Mausbewegungen Entropie gewinnt. Der implementierte JavaScript Client verschlĂŒsselt erfolgreich Stimmzettel mittels DamgĂ„rd- Jurik VerschlĂŒsselungsalgorithmus und leitet das Chiffrat mit zusĂ€tzlichen, fĂŒr den Zero-Knowledge Proofs Protokoll notwendigen Parametern im JSON Format an den Server weiter, der die empfangenen Daten auf ihre Wohlgeformtheit prĂŒft. Die Messungen haben ergeben, dass der Google Chrome Browser am optimalsten mit den angewendeten Libraries lĂ€uft. Bei der Verwendung eines 1024 Bit RSA Modulus benötigt der Google Chrome Browser 1.7 Sekunden fĂŒr die DamgĂ„rd- Jurik VerschlĂŒsselung und zusĂ€tzlich 8.8 Sekunden fĂŒr die Generierung der Zero-Knowledge Proofs Protokoll notwendigen Parametern.
Abhilasha Bhargav-Spantzel, Anna Squicciarini, Rui Xue, Elisa Bertino
The problem of identity theft, that is, the act of impersonating others' identities by presenting stolen identifiers or proofs of identities, has been receiving increasing attention because of its high financial and social costs. In this paper, we address the problem of verification of such identifiers and proofs of identity. Our approach is based on the concept of privacy preserving multifactor verification of such identifiers and proofs achieved by the development of a new cryptographic primitive, which uses aggregate signatures on commitments that are then used for aggregate zero-knowledge proof of knowledge (ZKPK) protocols. The resultant signatures are very short and the ZKPs are succinct and efficient. We prove the security of our scheme under the co-gap Diffie-Hellman (co-GDH) assumption for groups with bilinear maps. Our cryptographic scheme is an improvement in terms of the performance, flexibility, and storage requirements than the existing efficient ZKPK techniques that may be used to prove under zero knowledge and the knowledge of multiple secrets.
Based on the interactive proof of Hamiltonian Cycle (HC) of large directed graph, which is a $\Sigma$-protocol, we construct a perfectly hiding and computationally binding trapdoor commitment in 2-round from any one-way permutation. Then, based on this trapdoor commitment, we construct perfect zero-knowledge argument of knowledge with negligible error probability in 2-round for $\mathcal{NP}$, assuming only the existence of a one-way permutation.
In ESS2008, Yang et al. suggested a key-exposure-free chameleon hashing scheme, and it can be used to design signature and some other cryptography mechanism. In this paper, we construct a new timeliness optimistic fair exchange protocol based on this key-exposure-free chameleon hashing scheme. The new scheme does not require the use of interactive zero-knowledge proofs in the exchange phase. In our scheme, both parties can contact the trusted third party and settle the argument before the deadline. Moreover, the new scheme achieves fairness and timeliness.
DAA scheme in the TCG specification is based on CL signature,which is also combined by group signature and zero knowledge proof techniques to prove the direct anonymous attestation,and its security is based on the decomposition of large numbers.With the increasement of computer performance and the development of cryptography,the problem based on integer factorization problem is likely to be attacked,the corresponding DAA scheme has become no longer safety.But the algorithm based on the elliptic curve discrete logarithm and the prime on the discrete logarithm (double discrete logarithm) can use a shorter key,achieve higher security.Based on double discrete logarithm algorithm,this article designed a new DAA scheme.Demonstrated by analyzing solution,this new DAA scheme could not only meet the requirements of direct anonymous attestation,but also could make the implementation efficiency of the scheme consistent with the original one,while improved its security greatly.
With the secret distribution of a publicly verifiable secret sharing accomplished,k old participants take the place of the dealer to distribute new shares to new participants when the dealer is off-line and new participants want to share the secret. This paper presents a more general (k,n+t) scheme transformed from the (k,n) scheme based on the publicly verifiable secret sharing scheme and non-interactive zero-knowledge proof when t(tâ„1) new participants attach to the scheme. The (k,n+t) secret sharing scheme is publicly verifiable with the access structure and the former shares unchanged. Comparison with conventional publicly verifiable secret sharing schemes with enrollment ability shows that the (k,n+t) scheme flexibly allows multiple new participants to share the secret and reduces the public parameters and computational complexity.
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
A novel fair and efficient divisible E-Cash system based on the schnorr blind signature and non-interactive zero-knowledge proofs is proposed in this paper.In this system,both discrete logarithm and collision-resistance Hash function are used in the computation of divisible E-Cash.It contains the C value which defines the security.C can only be C1or be obtained by associated by C1and C2,where C1 is able to disclose the users' ID when over-spending happened.Moreover,the combination of and can realized owner tracing and coin tracing through the cooperation of B and T more easily.The scheme can also realize overspending tracing and over-deposit user,furthermore,it can limit the power of T,avoid the possibility of the association guilt between B and T.
For most present threshold signature schemes,sub-sign member can not sign a message anonymously or theirs anonymity is very weak.To improve their anonymity,a strong anonymity (n,t) threshold signature scheme based on DAA (Direct Anonymous Attestation),which is adopted by Trusted Computing Group v1.2 specifications,is proposed.Compared with the others,the scheme colligates DAA,zero-knowledge proof and Feldman verifiable secret sharing technique to achieve untraceable sub-sign and insure strong anonymity of signers,even the verifier and the dealer are colluded.Besides strong anonymity,analysis shows the scheme also has the property of unforgeable share,verifiable sub-sign,and robustness etc.It can be used in the situations which desire high-level anonymity such as anonymous voting.
In recent years, the studies of blind signatures achieved a lot of results, but there still are many problems. Boneh and Boyen gave a new signature, derived the blind signature scheme from their idea. This paper first gave a blind signature without random oracles, with this property, the scheme was secure in standard model. Then, used common reference string to do non-interactive zero knowledge proof, made the blind signature into only two moves to achieve round optimal, and the concurrency operation of blind signature could be reach by this. For the algorithm is simple and not complicated, the blind signature is more efficient than the existing secure blind signature schemes,so save transmission bandwidth and improves transfer efficiency.
We deisgn a DAA scheme based on Short Group Signature on l-MOMSDH assumption.On the basis of Fiat-Shamir heuristic theory,the signature of knowledge and realization of the transformation from non-interactive zero knowledge proof to signature of knowledge are introduced.Because of its short signature,high efficiency and provable security in Standard Model,the security of DAA is increased while its efficiency is also guaranteed.
Abstract : Mobile airborne networks deployed and used by the armed forces face significant challenges in balancing security concerns with reliably servicing the needs of the forces dependent on it. These issues are complicated by the ever-changing collaborative environments that these networks are tasked to support. The Zero Knowledge Protocol (ZKP) is a powerful technique that replaces the portion of a traditional credential-based key management system where credentials are exchanged. Instead, in ZKPs a proof of the existence of the credential is sent, allowing the receiver to develop absolute confidence that the user has a valid credential, without exposing the credential to risk of compromise. Based on the results of this research, we assert that it may be possible to construct a ZKP scheme with strong anonymity given any identification protocol and a shared-key update scheme.
In a digital world, usersâ Personally Identifiable Information (PII) is normally managed with a system called an Identity Management System (IMS). There are many types of IMSs. There are situations when two or more IMSs need to communicate with each other (such as when a service provider needs to obtain some identity information about a user from a trusted identity provider). There could be interoperability issues when communicating parties use different types of IMS. To facilitate interoperability between different IMSs, an Identity Meta System (IMetS) is normally used. An IMetS can, at least theoretically, join various types of IMSs to make them interoperable and give users the illusion that they are interacting with just one IMS. However, due to the complexity of an IMS, attempting to join various types of IMSs is a technically challenging task, let alone assessing how well an IMetS manages to integrate these IMSs. The first contribution of this thesis is the development of a generic IMS model called the Layered Identity Infrastructure Model (LIIM). Using this model, we develop a set of properties that an ideal IMetS should provide. This idealized form is then used as a benchmark to evaluate existing IMetSs. Different types of IMS provide varying levels of privacy protection support. Unfortunately, as observed by Josang et al (2007), there is insufficient privacy protection in many of the existing IMSs. In this thesis, we study and extend a type of privacy enhancing technology known as an Anonymous Credential System (ACS). In particular, we extend the ACS which is built on the cryptographic primitives proposed by Camenisch, Lysyanskaya, and Shoup. We call this system the Camenisch, Lysyanskaya, Shoup - Anonymous Credential System (CLS-ACS). The goal of CLS-ACS is to let users be as anonymous as possible. Unfortunately, CLS-ACS has problems, including (1) the concentration of power to a single entity - known as the Anonymity Revocation Manager (ARM) - who, if malicious, can trivially reveal a userâs PII (resulting in an illegal revocation of the userâs anonymity), and (2) poor performance due to the resource-intensive cryptographic operations required. The second and third contributions of this thesis are the proposal of two protocols that reduce the trust dependencies on the ARM during usersâ anonymity revocation. Both protocols distribute trust from the ARM to a set of n referees (n > 1), resulting in a significant reduction of the probability of an anonymity revocation being performed illegally. The first protocol, called the User Centric Anonymity Revocation Protocol (UCARP), allows a userâs anonymity to be revoked in a user-centric manner (that is, the user is aware that his/her anonymity is about to be revoked). The second protocol, called the Anonymity Revocation Protocol with Re-encryption (ARPR), allows a userâs anonymity to be revoked by a service provider in an accountable manner (that is, there is a clear mechanism to determine which entity who can eventually learn - and possibly misuse - the identity of the user). The fourth contribution of this thesis is the proposal of a protocol called the Private Information Escrow bound to Multiple Conditions Protocol (PIEMCP). This protocol is designed to address the performance issue of CLS-ACS by applying the CLS-ACS in a federated single sign-on (FSSO) environment. Our analysis shows that PIEMCP can both reduce the amount of expensive modular exponentiation operations required and lower the risk of illegal revocation of usersâ anonymity. Finally, the protocols proposed in this thesis are complex and need to be formally evaluated to ensure that their required security properties are satisfied. In this thesis, we use Coloured Petri nets (CPNs) and its corresponding state space analysis techniques. All of the protocols proposed in this thesis have been formally modeled and verified using these formal techniques. Therefore, the fifth contribution of this thesis is a demonstration of the applicability of CPN and its corresponding analysis techniques in modeling and verifying privacy enhancing protocols. To our knowledge, this is the first time that CPN has been comprehensively applied to model and verify privacy enhancing protocols. From our experience, we also propose several CPN modeling approaches, including complex cryptographic primitives (such as zero-knowledge proof protocol) modeling, attack parameterization, and others. The proposed approaches can be applied to other security protocols, not just privacy enhancing protocols.
In this paper, based on the verifiable pair and identity-based threshold cryptography, a novel identity-based (ID-based) threshold decryption scheme (IDTDS) is proposed, which is provably secure against adaptive chosen ciphertext attack under the computational bilinear Diffie-Hellman (CBDH) problem assumption in the random oracle. The pubic checkability of ciphertext in the IDTDS is given by simply creating a signed ElGamal encryption instead of a noninteractive zero-knowledge proof. Furthermore, we introduce a modified verifiable pairing to ensure all decryption shares are consistent. Our scheme is more efficient in verification than the schemes considered previously.