Sakai-Ohgishi-Kasahara Identity-Based Non-Interactive Key Exchange Revisited and More

Identity-based non-interactive key exchange (IB-NIKE) is a powerful but a bit overlooked primitive in identity-based cryptography. While identity-based encryption and signature have been extensively investigated over the past three decades, IB-NIKE has remained largely unstudied. Currently, there are only few IB-NIKE schemes in the literature. Among them, Sakai-Ohgishi-Kasahara (SOK) scheme is the first efficient and secure two-party IB-NIKE scheme, which has great influence on follow-up works. However, the SOK scheme required its identity mapping function to be modeled as a random oracle to prove security. Moreover, its existing security proof heavily relies on the ability of programming the random oracle. It is unknown whether such reliance is inherent. In this work, we intensively revisit the SOK IB-NIKE scheme, and present a series of possible and impossible results in the random oracle model and the standard model. In the random oracle model, we first improve previous security analysis for the SOK IB-NIKE scheme by giving a tighter reduction. We then use meta-reduction technique to show that the SOK scheme is unlikely proven to be secure based on the computational bilinear Diffie-Hellman (CBDH) assumption without programming the random oracle. In the standard model, we show how to instantiate the random oracle in the SOK scheme with a concrete hash function from admissible hash functions (AHFs) and indistinguishability obfuscation. The resulting scheme is adaptively secure based on the decisional bilinear Diffie-Hellman inversion (DBDHI) assumption. To the best of our knowledge, this is the first adaptively secure IB-NIKE scheme in the standard model that does not explicitly require multilinear maps. Previous schemes in the standard model either have merely selective security or require programmable hash functions in the multilinear setting. At the technical heart of our scheme, we generalize the definition of AHFs, and propose a generic construction which enables AHFs with previously unachieved parameters, which might be of independent interest. In addition, we present some new results about IB-NIKE. On the first place, we present a generic construction of multiparty IB-NIKE from extractable witness PRFs and existentially unforgeable signatures. On the second place, we investigate the relation between semi-adaptive security and adaptive security for IB-NIKE. Somewhat surprisingly, we show that these two notions are polynomially equivalent

Identity-Based Matchmaking Encryption, Revisited: Strong Security and Practical Constructions from Standard Classical and Post-Quantum Assumptions

Identity-based matchmaking encryption (IB-ME) [Ateniese et al. Crypto 2019] allows users to communicate privately in an anonymous and authenticated manner. After the seminal paper by Ateniese et al., a lot of work has been done on the security and construction of IB-ME. In this work, we revisit the security definitions and construction of IB-ME and provide the following three contributions. -- First, we embark on the task of classifying the existing security notions of IB-ME. We systematically categorize privacy into three core categories (CPA, CCA, and privacy in the case of mismatch) and authenticity into four categories (NMA and CMA both against insiders and outsiders). In particular, we reconsider privacy when the sender\u27s identity is mismatched during decryption, considered as ``enhanced privacy\u27\u27~[Francati et al., INDOCRYPT 2021], and provide a new simple security game, called mismatch security, that captures the essence of it. This structured framework not only facilitates more precise comparisons between different IB-ME schemes, but also serves as a valuable tool for evaluating the security of newly proposed schemes. -- Second, we propose a highly efficient and strongly secure IB-ME scheme from the bilinear Diffie-Hellman assumption in the random oracle model. The scheme is based on the Ateniese et al. scheme, but we introduce several techniques to improve its security and efficiency. Especially, we found that the Fujisaki-Okamoto transformation enhances not only privacy but also authenticity. As a result, we obtain a scheme that offers a more compact decryption key and ciphertext than the Ateniese et al. scheme, while achieving CCA and CMA, and mismatch security. -- Third, we propose a new generic construction of IB-ME from anonymous identity-based encryption, identity-based signature, and reusable extractors. Our construction not only achieves CCA, CMA, and mismatch security, but is also the most efficient among existing generic constructions. Through this construction, we obtain various IB-ME schemes from both classical and post-quantum assumptions. For example, we obtain a more efficient scheme from the symmetric external Diffie-Hellman assumption in the standard model, and a practical scheme from lattices in the quantum random oracle model whose secret keys and ciphertexts are less than 5 kilobytes. Moreover, our generic construction produces the first pairing-free IB-ME scheme in the standard model and the first tightly secure lattice-based IB-ME scheme in the quantum random oracle model

An advanced Study on Cryptography Mechanisms for Wireless Sensor Networks

Wireless Sensor Network (WSN) is consisting of independent and distributed sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. The most crucial and fundamental challenge facing WSN is security. Due to minimum capacity in-term of memory cost, processing and physical accessibility to sensors devices the security attacks are problematic. They are mostly deployed in open area, which expose them to different kinds of attacks. In this paper, we present an illustration of different attacks and vulnerabilities in WSN. Then we describe and analyze security requirement, countermeasures based on cryptography mechanisms in literature. Finally, we present possible directions in future research

Pairing-based cryptosystems and key agreement protocols.

For a long time, pairings on elliptic curves have been considered to be destructive in elliptic curve cryptography. Only recently after some pioneering works, particularly the well-known Boneh-Franklin identity-based encryption (IBE), pairings have quickly become an important tool to construct novel cryptographic schemes. In this thesis, several new cryptographic schemes with pairings are proposed, which are both efficient and secure with respect to a properly defined security model, and some relevant previous schemes are revisited. IBE provides a public key encryption mechanism where a public key can be an arbitrary string such as an entity identifier and unwieldy certificates are unnecessary. Based on the Sakai-Kasahara key construction, an IBE scheme which is secure in the Boneh-Franklin IBE model is constructed, and two identity-based key encapsulation mechanisms are proposed. These schemes achieve the best efficiency among the existing schemes to date. Recently Al-Riyami and Paterson introduced the certificateless public key encryption (CL-PKE) paradigm, which eliminates the need of certificates and at the same time retains the desirable properties of IBE without the key escrow problem. The security formulation of CL-PKE is revisited and a strong security model for this type of mechanism is defined. Following a heuristic approach, three efficient CL-PKE schemes which are secure in the defined strong security model are proposed. Identity-based two-party key agreement protocols from pairings are also investigated. The Bellare-Rogaway key agreement model is enhanced and within the model several previously unproven protocols in the literature are formally analysed. In considering that the user identity may be sensitive information in many environments, an identity-based key agreement protocol with unilateral identity privacy is proposed

Cryptographic Key Distribution In Wireless Sensor Networks Using Bilinear Pairings

It is envisaged that the use of cheap and tiny wireless sensors will soon bring a third wave of evolution in computing systems. Billions of wireless senor nodes will provide a bridge between information systems and the physical world. Wireless nodes deployed around the globe will monitor the surrounding environment as well as gather information about the people therein. It is clear that this revolution will put security solutions to a great test. Wireless Sensor Networks (WSNs) are a challenging environment for applying security services. They differ in many aspects from traditional fixed networks, and standard cryptographic solutions cannot be used in this application space. Despite many research efforts, key distribution in WSNs still remains an open problem. Many of the proposed schemes suffer from high communication overhead and storage costs, low scalability and poor resilience against different types of attacks. The exclusive usage of simple and energy efficient symmetric cryptography primitives does not solve the security problem. On the other hand a full public key infrastructure which uses asymmetric techniques, digital signatures and certificate authorities seems to be far too complex for a constrained WSN environment. This thesis investigates a new approach to WSN security which addresses many of the shortcomings of existing mechanisms. It presents a detailed description on how to provide practical Public Key Cryptography solutions for wireless sensor networks. The contributions to the state-of-the-art are added on all levels of development beginning with the basic arithmetic operations and finishing with complete security protocols. This work includes a survey of different key distribution protocols that have been developed for WSNs, with an evaluation of their limitations. It also proposes Identity- Based Cryptography (IBC) as an ideal technique for key distribution in sensor networks. It presents the first in-depth study of the application and implementation of Pairing- Based Cryptography (PBC) to WSNs. This is followed by a presentation of the state of the art on the software implementation of Elliptic Curve Cryptography (ECC) on typical WSNplatforms. New optimized algorithms for performing multiprecision multiplication on a broad range of low-end CPUs are introduced as well. Three novel protocols for key distribution are proposed in this thesis. Two of these are intended for non-interactive key exchange in flat and clustered networks respectively. A third key distribution protocol uses Identity-Based Encryption (IBE) to secure communication within a heterogeneous sensor network. This thesis includes also a comprehensive security evaluation that shows that proposed schemes are resistant to various attacks that are specific to WSNs. This work shows that by using the newest achievements in cryptography like pairings and IBC it is possible to deliver affordable public-key cryptographic solutions and to apply a sufficient level of security for the most demanding WSN applications