A Pairing-free Provable Secure and Efficient Identity-based Identification Scheme with Anonymity

In this paper, we propose a Blind Identity-Based Identification (Blind IBI) scheme based on the Guillou-Quisquater (GQ) scheme. Our proposed scheme combines the benefits of traditional Identity-Based Identification (IBI) schemes that can authenticate a user’s identity without rely ing on a trusted third party with the Blind Signature (BS) scheme that provides anonymity. As a result, the proposed scheme assures absolute user privacy during the authentication process. It does not rely on a third party, yet the verifier can still be assured of the user’s identity with out the user actually revealing it. In our work, we show that the proposed scheme is provably secure under the random oracle model, with the assumption that the one-more-RSA-inversion problem is difficult. Furthermore, we demonstrate that the proposed scheme is secure against passive, active, and concurrent impersonation attacks. In conclusion, the proposed scheme is able to achieve the desired blindness property without compromising the security of the GQ-IBI scheme it is based upon

An efficient identification scheme in standard model based on the diophantine equation hard problem

Recently the Diophantine Equation Hard Problem (DEHP) was proposed. It is utilized to design a standard identification scheme model. Since the computation involves only simple addition and multiplication steps, the efficiency and the time cost are greatly improved as compared to the existing identification schemes. In this paper, we propose a zero knowledge identification scheme based upon the DEHP. With the assumption such that DEHP is intractable, we provide the security analysis on the impersonation against non-adaptive passive attack (imp-pa) and show that our new proposed scheme is more desirable due to high efficiency in terms of time computation

Security Proofs for Identity-Based Identification and Signature Schemes

This paper provides either security proofs or attacks for a large number of identity-based identification and signature schemes defined either explicitly or implicitly in existing literature. Underlying these is a framework that on the one hand helps explain how these schemes are derived, and on the other hand enables modular security analyses, thereby helping to understand, simplify and unify previous work. We also analyze a generic folklore construction that in particular yields identity-based identification and signature schemes without random oracles

Lattice-Based Group Signatures: Achieving Full Dynamicity (and Deniability) with Ease

In this work, we provide the first lattice-based group signature that offers full dynamicity (i.e., users have the flexibility in joining and leaving the group), and thus, resolve a prominent open problem posed by previous works. Moreover, we achieve this non-trivial feat in a relatively simple manner. Starting with Libert et al.'s fully static construction (Eurocrypt 2016) - which is arguably the most efficient lattice-based group signature to date, we introduce simple-but-insightful tweaks that allow to upgrade it directly into the fully dynamic setting. More startlingly, our scheme even produces slightly shorter signatures than the former, thanks to an adaptation of a technique proposed by Ling et al. (PKC 2013), allowing to prove inequalities in zero-knowledge. Our design approach consists of upgrading Libert et al.'s static construction (EUROCRYPT 2016) - which is arguably the most efficient lattice-based group signature to date - into the fully dynamic setting. Somewhat surprisingly, our scheme produces slightly shorter signatures than the former, thanks to a new technique for proving inequality in zero-knowledge without relying on any inequality check. The scheme satisfies the strong security requirements of Bootle et al.'s model (ACNS 2016), under the Short Integer Solution (SIS) and the Learning With Errors (LWE) assumptions. Furthermore, we demonstrate how to equip the obtained group signature scheme with the deniability functionality in a simple way. This attractive functionality, put forward by Ishida et al. (CANS 2016), enables the tracing authority to provide an evidence that a given user is not the owner of a signature in question. In the process, we design a zero-knowledge protocol for proving that a given LWE ciphertext does not decrypt to a particular message

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

Social, Private, and Trusted Wearable Technology under Cloud-Aided Intermittent Wireless Connectivity

There has been an unprecedented increase in the use of smart devices globally, together with novel forms of communication, computing, and control technologies that have paved the way for a new category of devices, known as high-end wearables. While massive deployments of these objects may improve the lives of people, unauthorized access to the said private equipment and its connectivity is potentially dangerous. Hence, communication enablers together with highly-secure human authentication mechanisms have to be designed.In addition, it is important to understand how human beings, as the primary users, interact with wearable devices on a day-to-day basis; usage should be comfortable, seamless, user-friendly, and mindful of urban dynamics. Usually the connectivity between wearables and the cloud is executed through the user’s more power independent gateway: this will usually be a smartphone, which may have potentially unreliable infrastructure connectivity. In response to these unique challenges, this thesis advocates for the adoption of direct, secure, proximity-based communication enablers enhanced with multi-factor authentication (hereafter refereed to MFA) that can integrate/interact with wearable technology. Their intelligent combination together with the connection establishment automation relying on the device/user social relations would allow to reliably grant or deny access in cases of both stable and intermittent connectivity to the trusted authority running in the cloud.The introduction will list the main communication paradigms, applications, conventional network architectures, and any relevant wearable-specific challenges. Next, the work examines the improved architecture and security enablers for clusterization between wearable gateways with a proximity-based communication as a baseline. Relying on this architecture, the author then elaborates on the social ties potentially overlaying the direct connectivity management in cases of both reliable and unreliable connection to the trusted cloud. The author discusses that social-aware cooperation and trust relations between users and/or the devices themselves are beneficial for the architecture under proposal. Next, the author introduces a protocol suite that enables temporary delegation of personal device use dependent on different connectivity conditions to the cloud.After these discussions, the wearable technology is analyzed as a biometric and behavior data provider for enabling MFA. The conventional approaches of the authentication factor combination strategies are compared with the ‘intelligent’ method proposed further. The assessment finds significant advantages to the developed solution over existing ones.On the practical side, the performance evaluation of existing cryptographic primitives, as part of the experimental work, shows the possibility of developing the experimental methods further on modern wearable devices.In summary, the set of enablers developed here for wearable technology connectivity is aimed at enriching people’s everyday lives in a secure and usable way, in cases when communication to the cloud is not consistently available

Two-Tier Signatures, Strongly Unforgeable Signatures, and Fiat-Shamir without Random Oracles

We show how the Fiat-Shamir transform can be used to convert three-move identification protocols into two-tier signature schemes (a primitive we define) with a proof of security that makes a standard assumption on the hash function rather than modeling it as a random oracle. The result requires security of the starting protocol against concurrent attacks. We can show that numerous protocols have the required properties and so obtain numerous efficient two-tier schemes. Our first application is an efficient transform of any unforgeable signature scheme into a strongly unforgeable one, which uses as a tool any two-tier scheme. (This extends work of Boneh, Shen and Waters whose transform only applies to a limited class of schemes.) The second application is new one-time signature schemes that, compared to one-way function based ones of the same computational cost, have smaller key and signature sizes

Why Cryptography Should Not Rely on Physical Attack Complexity

This book presents two practical physical attacks. It shows how attackers can reveal the secret key of symmetric as well as asymmetric cryptographic algorithms based on these attacks, and presents countermeasures on the software and the hardware level that can help to prevent them in the future. Though their theory has been known for several years now, since neither attack has yet been successfully implemented in practice, they have generally not been considered a serious threat. In short, their physical attack complexity has been overestimated and the implied security threat has been underestimated. First, the book introduces the photonic side channel, which offers not only temporal resolution, but also the highest possible spatial resolution. Due to the high cost of its initial implementation, it has not been taken seriously. The work shows both simple and differential photonic side channel analyses. Then, it presents a fault attack against pairing-based cryptography. Due to the need for at least two independent precise faults in a single pairing computation, it has not been taken seriously either. Based on these two attacks, the book demonstrates that the assessment of physical attack complexity is error-prone, and as such cryptography should not rely on it. Cryptographic technologies have to be protected against all physical attacks, whether they have already been successfully implemented or not. The development of countermeasures does not require the successful execution of an attack but can already be carried out as soon as the principle of a side channel or a fault attack is sufficiently understood

Anonymous Credentials Light

We define and propose an efficient and provably secure construction of blind signatures with attributes. Prior notions of blind signatures did not yield themselves to the construction of anonymous credential systems, not even if we drop the unlinkability requirement of anonymous credentials. Our new notion in contrast is a convenient building block for anonymous credential systems. The construction we propose is efficient: it requires just a few exponentiations in a prime-order group in which the decisional Diffie-Hellman problem is hard. Thus, for the first time, we give a provably secure construction of anonymous credentials that can work in the elliptic group setting without bilinear pairings. In contrast, prior provably secure constructions were based on the RSA group or on groups with pairings, which made them prohibitively inefficient for mobile devices, RFIDs and smartcards. The only prior efficient construction that could work in such elliptic curve groups, due to Brands, does not have a proof of security

An implementation of accountable anonymity

Complex well developed and established Anonymity systems lack Accountability. These systems offer unconditional anonymity to their users which can stimulate abusive behavior. Controlling abuse should be equally important as protecting the anonymity of legitimate users when designing anonymous applications. Current anonymity systems are promoted to family and friends, businesses, activists and the media. However, these same systems could potentially be used for: sending offensive email, spam, copyrighted material, cyber warfare, child pornography, pedophiles chatting with kids online or any other illegal activity performed on the Internet. Freedom of speech and the First Amendment allows people to express their opinions and choose any anonymity service and by no means will people be forced to use this system. In this thesis, a model that allows an anonymous yet accountable method of communication on the Internet is introduced. The design and implementation is based on a new proxy-re-encryption scheme and a modifed onion routing scheme. Techniques for Accountable Anonymity are demonstrated by building a lightweight prototype. In this system, users are registered in the system\u27s database in order to use it. In this research, the total network latency is signifcantly smaller when sending data over the network compared to The onion router (Tor) system which makes it deployable to use at a larger scale system. Also, the Accountable Anonymity system\u27s digital forensic mode makes it easier to track the perpetrators