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

Research on security and privacy in vehicular ad hoc networks

Los sistemas de redes ad hoc vehiculares (VANET) tienen como objetivo proporcionar una plataforma para diversas aplicaciones que pueden mejorar la seguridad vial, la eficiencia del tráfico, la asistencia a la conducción, la regulación del transporte, etc. o que pueden proveer de una mejor información y entretenimiento a los usuarios de los vehículos. Actualmente se está llevando a cabo un gran esfuerzo industrial y de investigación para desarrollar un mercado que se estima alcance en un futuro varios miles de millones de euros. Mientras que los enormes beneficios que se esperan de las comunicaciones vehiculares y el gran número de vehículos son los puntos fuertes de las VANET, su principal debilidad es la vulnerabilidad a los ataques contra la seguridad y la privacidad.En esta tesis proponemos cuatro protocolos para conseguir comunicaciones seguras entre vehículos. En nuestra primera propuesta empleamos a todas las unidades en carretera (RSU) para mantener y gestionar un grupo en tiempo real dentro de su rango de comunicación. Los vehículos que entren al grupo de forma anónima pueden emitir mensajes vehículo a vehículo (V2V) que inmediatamente pueden ser verificados por los vehículos del mismo grupo (y grupos de vecinos). Sin embargo, en la primera fase del despliegue de este sistema las RSU pueden no estar bien distribuídas. Consecuentemente, se propone un conjunto de mecanismos para hacer frente a la seguridad, privacidad y los requisitos de gestión de una VANET a gran escala sin la suposición de que las RSU estén densamente distribuidas. La tercera propuesta se centra principalmente en la compresión de las evidencias criptográficas que nos permitirán demostrar, por ejemplo, quien era el culpable en caso de accidente. Por último, investigamos los requisitos de seguridad de los sistemas basados en localización (LBS) sobre VANETs y proponemos un nuevo esquema para la preservación de la privacidad de la localización en estos sistemas sobre dichas redes.Vehicular ad hoc network (VANET) systems aim at providing a platform for various applications that can improve traffic safety and efficiency, driver assistance, transportation regulation, infotainment, etc. There is substantial research and industrial effort to develop this market. It is estimated that the market for vehicular communications will reach several billion euros. While the tremendous benefits expected from vehicular communications and the huge number of vehicles are strong points of VANETs, their weakness is vulnerability to attacks against security and privacy.In this thesis, we propose four protocols for secure vehicle communications. In our first proposal, we employ each road-side unit (RSU) to maintain and manage an on-the-fly group within its communication range. Vehicles entering the group can anonymously broadcast vehicle-to-vehicle (V2V) messages, which can be instantly verified by the vehicles in the same group (and neighbor groups). However, at the early stage of VANET deployment, the RSUs may not be well distributed. We then propose a set of mechanisms to address the security, privacy, and management requirements of a large-scale VANET without the assumption of densely distributed RSUs. The third proposal is mainly focused on compressing cryptographic witnesses in VANETs. Finally, we investigate the security requirements of LBS in VANETs and propose a new privacy-preserving LBS scheme for those networks

Research Philosophy of Modern Cryptography

Proposing novel cryptography schemes (e.g., encryption, signatures, and protocols) is one of the main research goals in modern cryptography. In this paper, based on more than 800 research papers since 1976 that we have surveyed, we introduce the research philosophy of cryptography behind these papers. We use ``benefits and ``novelty as the keywords to introduce the research philosophy of proposing new schemes, assuming that there is already one scheme proposed for a cryptography notion. Next, we introduce how benefits were explored in the literature and we have categorized the methodology into 3 ways for benefits, 6 types of benefits, and 17 benefit areas. As examples, we introduce 40 research strategies within these benefit areas that were invented in the literature. The introduced research strategies have covered most cryptography schemes published in top-tier cryptography conferences

Lightweight identity based online/offline signature scheme for wireless sensor networks

Data security is one of the issues during data exchange between two sensor nodes in wireless sensor networks (WSN). While information flows across naturally exposed communication channels, cybercriminals may access sensitive information. Multiple traditional reliable encryption methods like RSA encryption-decryption and Diffie–Hellman key exchange face a crisis of computational resources due to limited storage, low computational ability, and insufficient power in lightweight WSNs. The complexity of these security mechanisms reduces the network lifespan, and an online/offline strategy is one way to overcome this problem. This study proposed an improved identity-based online/offline signature scheme using Elliptic Curve Cryptography (ECC) encryption. The lightweight calculations were conducted during the online phase, and in the offline phase, the encryption, point multiplication, and other heavy measures were pre-processed using powerful devices. The proposed scheme uniquely combined the Inverse Collusion Attack Algorithm (CAA) with lightweight ECC to generate secure identitybased signatures. The suggested scheme was analyzed for security and success probability under Random Oracle Model (ROM). The analysis concluded that the generated signatures were immune to even the worst Chosen Message Attack. The most important, resource-effective, and extensively used on-demand function was the verification of the signatures. The low-cost verification algorithm of the scheme saved a significant number of valued resources and increased the overall network’s lifespan. The results for encryption/decryption time, computation difficulty, and key generation time for various data sizes showed the proposed solution was ideal for lightweight devices as it accelerated data transmission speed and consumed the least resources. The hybrid method obtained an average of 66.77% less time consumption and up to 12% lower computational cost than previous schemes like the dynamic IDB-ECC two-factor authentication key exchange protocol, lightweight IBE scheme (IDB-Lite), and Korean certification-based signature standard using the ECC. The proposed scheme had a smaller key size and signature size of 160 bits. Overall, the energy consumption was also reduced to 0.53 mJ for 1312 bits of offline storage. The hybrid framework of identity-based signatures, online/offline phases, ECC, CAA, and low-cost algorithms enhances overall performance by having less complexity, time, and memory consumption. Thus, the proposed hybrid scheme is ideally suited for a lightweight WSN

CONSTRUCTION OF EFFICIENT AUTHENTICATION SCHEMES USING TRAPDOOR HASH FUNCTIONS

In large-scale distributed systems, where adversarial attacks can have widespread impact, authentication provides protection from threats involving impersonation of entities and tampering of data. Practical solutions to authentication problems in distributed systems must meet specific constraints of the target system, and provide a reasonable balance between security and cost. The goal of this dissertation is to address the problem of building practical and efficient authentication mechanisms to secure distributed applications. This dissertation presents techniques to construct efficient digital signature schemes using trapdoor hash functions for various distributed applications. Trapdoor hash functions are collision-resistant hash functions associated with a secret trapdoor key that allows the key-holder to find collisions between hashes of different messages. The main contributions of this dissertation are as follows: 1. A common problem with conventional trapdoor hash functions is that revealing a collision producing message pair allows an entity to compute additional collisions without knowledge of the trapdoor key. To overcome this problem, we design an efficient trapdoor hash function that prevents all entities except the trapdoor key-holder from computing collisions regardless of whether collision producing message pairs are revealed by the key-holder. 2. We design a technique to construct efficient proxy signatures using trapdoor hash functions to authenticate and authorize agents acting on behalf of users in agent-based computing systems. Our technique provides agent authentication, assurance of agreement between delegator and agent, security without relying on secure communication channels and control over an agent’s capabilities. 3. We develop a trapdoor hash-based signature amortization technique for authenticating real-time, delay-sensitive streams. Our technique provides independent verifiability of blocks comprising a stream, minimizes sender-side and receiver-side delays, minimizes communication overhead, and avoids transmission of redundant information. 4. We demonstrate the practical efficacy of our trapdoor hash-based techniques for signature amortization and proxy signature construction by presenting discrete log-based instantiations of the generic techniques that are efficient to compute, and produce short signatures. Our detailed performance analyses demonstrate that the proposed schemes outperform existing schemes in computation cost and signature size. We also present proofs for security of the proposed discrete-log based instantiations against forgery attacks under the discrete-log assumption

Crytographic applications of bilinear maps

Bilinear maps have become an important new item in the cryptographer’s toolkit. They first came to prominence when they were used by Menezes, Okamoto and Vanstone to help solve the elliptic curve discrete logarithm problem on elliptic curves of small embedding degree. In 1984, Shamir developed the first identity based signature scheme, and posed the construction of an identity based encryption scheme as an open problem [118]. Subsequently identity based identification and identity based key agreement schemes were proposed. However, identity based encryption remained an open problem. In 2000, Sakai, Ohgishi and Kasahara used bilinear maps to implement an efficient identity based non-interactive key agreement and identity based digital signature [111]. In 2001, some 17 years after it was suggested, Boneh and Franklin proposed the first efficient identity based encryption scheme, constructed using bilinear maps [31]. In this thesis we review some of the numerous cryptographic protocols that have been constructed using bilinear maps. We first give a review of public key cryptography. We then review the mathematics behind the two known bilinear maps, the Weil and Tate pairings, including several improvements suggested m [67, 14]. We develop a Java library to implement pairing based cryptography. In Ch 4 we look at some of the cryptographically hard problems that arise from bilinear maps. In Ch 5 we review identity based signature schemes and present the fastest known scheme. In Ch 6 we review some encryption schemes, make some observations that help improve the performance of many identity based cryptosystems, and propose the fastest scheme for public key encryption with keyword search. In Ch 7 we review identity based key agreements and propose the fastest scheme secure in a modified Bellare-Rogaway model [19]. In Ch 8 we review identity based signcryption schemes and present the fastest known scheme

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

Critical Perspectives on Provable Security: Fifteen Years of Another Look Papers

We give an overview of our critiques of “proofs” of security and a guide to our papers on the subject that have appeared over the past decade and a half. We also provide numerous additional examples and a few updates and errata