Deniable Key Establishment Resistance against eKCI Attacks

In extended Key Compromise Impersonation (eKCI) attack against authenticated key establishment (AKE) protocols the adversary impersonates one party, having the long term key and the ephemeral key of the other peer party. Such an attack can be mounted against variety of AKE protocols, including 3-pass HMQV. An intuitive countermeasure, based on BLS (Boneh–Lynn–Shacham) signatures, for strengthening HMQV was proposed in literature. The original HMQV protocol fulfills the deniability property: a party can deny its participation in the protocol execution, as the peer party can create a fake protocol transcript indistinguishable from the real one. Unfortunately, the modified BLS based version of HMQV is not deniable. In this paper we propose a method for converting HMQV (and similar AKE protocols) into a protocol resistant to eKCI attacks but without losing the original deniability property. For that purpose, instead of the undeniable BLS, we use a modification of Schnorr authentication protocol, which is deniable and immune to ephemeral key leakages

Efficient and Provably-secure Certificateless Strong Designated Verifier Signature Scheme without Pairings

Strong designated verifier signature (generally abbreviated to SDVS) allows signers to obtain absolute control over who can verify the signature, while only the designated verifier other than anyone else can verify the validity of a SDVS without being able to transfer the conviction. Certificateless PKC has unique advantages comparing with certificate-based cryptosystems and identity-based PKC, without suffering from key escrow. Motivated by these attractive features, we propose a novel efficient CL-SDVS scheme without bilinear pairings or map-to-point hash operations. The proposed scheme achieves all the required security properties including EUF-CMA, non-transferability, strongness and non-delegatability. We also estimate the computational and communication efficiency. The comparison shows that our scheme outperforms all the previous CL-(S)DVS schemes. Furthermore, the crucial security properties of the CL-SDVS scheme are formally proved based on the intractability of SCDH and ECDL assumptions in random oracle model

Still Wrong Use of Pairings in Cryptography

Several pairing-based cryptographic protocols are recently proposed with a wide variety of new novel applications including the ones in emerging technologies like cloud computing, internet of things (IoT), e-health systems and wearable technologies. There have been however a wide range of incorrect use of these primitives. The paper of Galbraith, Paterson, and Smart (2006) pointed out most of the issues related to the incorrect use of pairing-based cryptography. However, we noticed that some recently proposed applications still do not use these primitives correctly. This leads to unrealizable, insecure or too inefficient designs of pairing-based protocols. We observed that one reason is not being aware of the recent advancements on solving the discrete logarithm problems in some groups. The main purpose of this article is to give an understandable, informative, and the most up-to-date criteria for the correct use of pairing-based cryptography. We thereby deliberately avoid most of the technical details and rather give special emphasis on the importance of the correct use of bilinear maps by realizing secure cryptographic protocols. We list a collection of some recent papers having wrong security assumptions or realizability/efficiency issues. Finally, we give a compact and an up-to-date recipe of the correct use of pairings.Comment: 25 page

Security in Key Agreement: Two-Party Certificateless Schemes

The main goal of cryptography is to enable secure communication over a public channel; often a secret shared among the communicating parties is used to achieve this. The process by which these parties agree on such a shared secret is called key agreement. In this thesis, we focus on two-party key agreement protocols in the public-key setting and study the various methods used to establish and validate public keys. We pay particular attention to certificateless key agreement schemes and attempt to formalize a relevant notion of security. To that end, we give a possible extension of the existing extended Canetti-Krawzcyk security model applicable to the certificateless setting. We observe that none of the certificateless protocols we have seen in the literature are secure in this model; it is an open question whether such schemes exist. We analyze several published certificateless key agreement protocols, demonstrating the existence of key compromise impersonation attacks and even a man-in-the-middle attack in one case, contrary to the claims of the authors. We also briefly describe weaknesses exhibited by these protocols in the context of our suggested security model

An Efficient Certificate-Based Designated Verifier Signature Scheme

Certificate-based public key cryptography not only solves certificate revocation problem in traditional PKI but also overcomes key escrow problem inherent in identity-based cryptosystems. This new primitive has become an attractive cryptographic paradigm. In this paper, we propose the notion and the security model of certificate-based designated verifier signatures (CBDVS). We provide the first construction of CBDVS and prove that our scheme is existentially unforgeable against adaptive chosen message attacks in the random oracle model. Our scheme only needs two pairing operations, and the signature is only one element in the bilinear group G1. To the best of our knowledge, our scheme enjoys shortest signature length with less operation cost

Authentication schemes for Smart Mobile Devices: Threat Models, Countermeasures, and Open Research Issues

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper presents a comprehensive investigation of authentication schemes for smart mobile devices. We start by providing an overview of existing survey articles published in the recent years that deal with security for mobile devices. Then, we give a classification of threat models in smart mobile devices in five categories, including, identity-based attacks, eavesdropping-based attacks, combined eavesdropping and identity-based attacks, manipulation-based attacks, and service-based attacks. This is followed by a description of multiple existing threat models. We also provide a classification of countermeasures into four types of categories, including, cryptographic functions, personal identification, classification algorithms, and channel characteristics. According to the characteristics of the countermeasure along with the authentication model iteself, we categorize the authentication schemes for smart mobile devices in four categories, namely, 1) biometric-based authentication schemes, 2) channel-based authentication schemes, 3) factors-based authentication schemes, and 4) ID-based authentication schemes. In addition, we provide a taxonomy and comparison of authentication schemes for smart mobile devices in form of tables. Finally, we identify open challenges and future research directions

Identity-Based Higncryption

Identity-based cryptography (IBC) is fundamental to security and privacy protection. Identity-based authenticated encryption (i.e., signcryption) is an important IBC primitive, which has numerous and promising applications. After two decades of research on signcryption,recently a new cryptographic primitive, named higncryption, was proposed. Higncryption can be viewed as privacy-enhanced signcryption, which integrates public key encryption, entity authentication, and identity concealment (which is not achieved in signcryption) into a monolithic primitive. Here, briefly speaking, identity concealment means that the transcript of protocol runs should not leak participants\u27 identity information. In this work, we propose the first identity-based higncryption (IBHigncryption). The most impressive feature of IBHigncryption, among others, is its simplicity and efficiency. The proposed IBHigncryption scheme is essentially as efficient as the fundamental CCA-secure Boneh-Franklin IBE scheme [18], while offering entity authentication and identity concealment simultaneously. Compared to the identity-based signcryption scheme [11], which is adopted in the IEEE P1363.3 standard, our IBHigncryption scheme is much simpler, and has significant efficiency advantage in total. Besides, our IBHigncryption enjoys forward ID-privacy, receiver deniability and x-security simultaneously. In addition, the proposed IBHigncryption has a much simpler setup stage with smaller public parameters, which in particular does not have the traditional master public key. Higncryption is itself one-pass identity-concealed authenticated key exchange without forward security for the receiver. Finally, by applying the transformation from higncryption to identity-concealed authenticated key exchange (CAKE), we get three-pass identity-based CAKE (IB-CAKE) with explicit mutual authentication and strong security (in particular, perfect forward security for both players). Specifically, the IB-CAKE protocol involves the composition of two runs of IBHigncryption, and has the following advantageous features inherited from IBHigncryption: (1) single pairing operation: each player performs only a single pairingoperation; (2) forward ID-privacy; (3) simple setup without master public key; (4) strong resilience to ephemeral state exposure, i.e., x-security; (5) reasonable deniability

Still Wrong Use of Pairings in Cryptography

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Several pairing-based cryptographic protocols are recently proposed with a wide variety of new novel applications including the ones in emerging technologies like cloud computing, internet of things (IoT), e-health systems and wearable technologies. There have been however a wide range of incorrect use of these primitives. The paper of Galbraith, Paterson, and Smart (2006) pointed out most of the issues related to the incorrect use of pairing-based cryptography. However, we noticed that some recently proposed applications still do not use these primitives correctly. This leads to unrealizable, insecure or too ine cient designs of pairing-based protocols. We observed that one reason is not being aware of the recent advancements on solving the discrete logarithm problems in some groups. The main purpose of this article is to give an understandable, informative, and the most up-to-date criteria for the correct use of pairing-based cryptography. We thereby deliberately avoid most of the technical details and rather give special emphasis on the importance of the correct use of bilinear maps by realizing secure cryptographic protocols. We list a collection of some recent papers having wrong security assumptions or realizability/e ciency issues. Finally, we give a compact and an up-to-date recipe of the correct use of pairings

Data storage security and privacy in cloud computing: A comprehensive survey

Cloud Computing is a form of distributed computing wherein resources and application platforms are distributed over the Internet through on demand and pay on utilization basis. Data Storage is main feature that cloud data centres are provided to the companies/organizations to preserve huge data. But still few organizations are not ready to use cloud technology due to lack of security. This paper describes the different techniques along with few security challenges, advantages and also disadvantages. It also provides the analysis of data security issues and privacy protection affairs related to cloud computing by preventing data access from unauthorized users, managing sensitive data, providing accuracy and consistency of data store

Location Privacy in VANETs: Improved Chaff-Based CMIX and Privacy-Preserving End-to-End Communication

VANETs communication systems are technologies and defined policies that can be formed to enable ITS applications to provide road traffic efficacy, warning about such issues as environmental dangers, journey circumstances, and in the provision of infotainment that considerably enhance transportation safety and quality. The entities in VANETs, generally vehicles, form part of a massive network known as the Internet of Vehicles (IoV). The deployment of large-scale VANETs systems is impossible without ensuring that such systems are themselves are safe and secure, protecting the privacy of their users. There is a risk that cars might be hacked, or their sensors become defective, causing inaccurate information to be sent across the network. Consequently, the activities and credentials of participating vehicles should be held responsible and quickly broadcast throughout a vast VANETs, considering the accountability in the system. The openness of wireless communication means that an observer can eavesdrop on vehicular communication and gain access or otherwise deduce users' sensitive information, and perhaps profile vehicles based on numerous factors such as tracing their travels and the identification of their home/work locations. In order to protect the system from malicious or compromised entities, as well as to preserve user privacy, the goal is to achieve communication security, i.e., keep users' identities hidden from both the outside world and the security infrastructure and service providers. Being held accountable while still maintaining one's privacy is a difficult balancing act. This thesis explores novel solution paths to the above challenges by investigating the impact of low-density messaging to improve the security of vehicle communications and accomplish unlinkability in VANETs. This is achieved by proposing an improved chaff-based CMIX protocol that uses fake messages to increase density to mitigate tracking in this scenario. Recently, Christian \etall \cite{vaas2018nowhere} proposed a Chaff-based CMIX scheme that sends fake messages under the presumption low-density conditions to enhance vehicle privacy and confuse attackers. To accomplish full unlinkability, we first show the following security and privacy vulnerabilities in the Christian \etall scheme: linkability attacks outside the CMIX may occur due to deterministic data-sharing during the authentication phase (e.g., duplicate certificates for each communication). Adversaries may inject fake certificates, which breaks Cuckoo Filters' (CFs) updates authenticity, and the injection may be deniable. CMIX symmetric key leakage outside the coverage may occur. We propose a VPKI-based protocol to mitigate these issues. First, we use a modified version of Wang \etall's \cite{wang2019practical} scheme to provide mutual authentication without revealing the real identity. To this end, a vehicle's messages are signed with a different pseudo-identity “certificate”. Furthermore, the density is increased via the sending of fake messages during low traffic periods to provide unlinkability outside the mix-zone. Second, unlike Christian \etall's scheme, we use the Adaptive Cuckoo Filter (ACF) instead of CF to overcome the effects of false positives on the whole filter. Moreover, to prevent any alteration of the ACFs, only RUSs distribute the updates, and they sign the new fingerprints. Third, mutual authentication prevents any leakage from the mix zones' symmetric keys by generating a fresh one for each communication through a Diffie–Hellman key exchange. As a second main contribution of this thesis, we focus on the V2V communication without the interference of a Trusted Third Party (TTP)s in case this has been corrupted, destroyed, or is out of range. This thesis presents a new and efficient end-to-end anonymous key exchange protocol based on Yang \etall's \cite{yang2015self} self-blindable signatures. In our protocol, vehicles first privately blind their own private certificates for each communication outside the mix-zone and then compute an anonymous shared key based on zero-knowledge proof of knowledge (PoK). The efficiency comes from the fact that once the signatures are verified, the ephemeral values in the PoK are also used to compute a shared key through an authenticated Diffie-Hellman key exchange protocol. Therefore, the protocol does not require any further external information to generate a shared key. Our protocol also does not require interfacing with the Roadside Units or Certificate Authorities, and hence can be securely run outside the mixed-zones. We demonstrate the security of our protocol in ideal/real simulation paradigms. Hence, our protocol achieves secure authentication, forward unlinkability, and accountability. Furthermore, the performance analysis shows that our protocol is more efficient in terms of computational and communications overheads compared to existing schemes.Kuwait Cultural Offic