Identity based encryption chatterjee sanjit sarkar palash
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In particular, we show that there is an interesting trade-off between the tightness of the security reduction and smallness of the public parameter. Ciphertext validity testing is done indirectly through a symmetric authentication algorithm in a manner similar to the Kurosawa-Desmedt public key encryption protocol. On the security front, for some well-known proto- cols we discuss to what extent the security arguments are tenable when one moves to genus-2 curves in the Type 1 case. A key feature of the construction is the presence of random tags in the ciphertext and decryption key. Many cryptographic protocols in the asymmetric setting rely on the existence of ψ for their security reduction while some use it in the protocol itself.

The inherent parallelism in each of the algorithms have been identified leading to optimal two-multiplier algorithm. We also propose an enhancement of the extended Canetti-Krawczyk security model and definition for the situation where static public keys are reused in two or more key agreement protocols. In the case of Type 4 pairings, our main contribution is a new method for hashing into G2 which makes the Type 4 setting almost as efficient as Type 3. We suggest significant improvements over their proposal in terms of client computation and communication resources by properly recasting it in two-party settings. Contrary to these widely held beliefs, we argue that Type 2 pairings are merely inefficient implementations of Type 3 pairings, and appear to offer no benefit for protocols based on asymmetric pairings from the point of view of functionality, security, and performance. Based on the in dependence conditions we propose a general framework of multiple forking and a General Multiple Forking Lemma. This therefore calls for an efficient solution that allows such subset based restricted search with constant trapdoor size.

By properly accounting for the actual structure of the underlying groups and subgroup membership testing of group elements in signatures, we show that the schemes are not as efficient as claimed. On the imple- mentation front, we report improved timings for Type 1 pairings derived from supersingular elliptic curves in characteristic 2 and 3 and the first timings for supersingular genus-2 curves in characteristic 2 at the 128-bit security level. Known examples of such maps arise from certain algebraic geometric objects. This book will also cover a brief background on Elliptic Curves and Pairings, security against chosen Cipher text Attacks, standards and more. We observe that the quadratic residue based property used in their separation result is a special case of testing equality of one-bit messages, suggest a very simple and efficient deterministic encryption scheme for testing equality and show that the two security notions, find-then-guess and left-or-right, are tightly equivalent in this setting.

The second construction requires exactly three additional ciphertext components but needs only one additional unit pairing evaluation during decryption. We revisit the work of Tseng et al. There are three previous protocols for this problem — two using the random oracle heuristic and one without. The purpose of the current chapter is to provide a brief summary of the products and the draft standards related to identity-based cryptography. In this paper, we observe that these attacks are in fact effective only on a small number of pairing-based protocols, and that too only when the protocols are implemented with specific symmetric pairings. For the security reduction, all of them assume certain hash functions to be independent and uniform random functions, i. Here we propose a generalisation of Waters scheme.

By implication, the cost of a single forking involving two random oracles augmented forking matches that involving a single random oracle elementary forking. . Both primitives are secure in their respective full models and have better efficiencies compared to previously known schemes offering the same level and type of security. Ciphertext validity testing is done indirectly through a symmetric authentication algorithm in a manner similar to the Kurosawa-Desmedt public key encryption protocol. The technique for answering decryption queries in the proof is based on earlier work by Boyen, Mei and Waters.

The first variation, called BasicIdent, is secure against adversaries that are not allowed to make decryption queries. We also formally establish that in the concrete mathematical structure of asymmetric pairing, all Type 2 structure-preserving signature schemes can be converted to the Type 3 setting without any penalty in security or efficiency, and show that the converse is false. Are there any cryptographic protocols whose security is based on a standard computational assumption but the security reduction does not depend on the random oracle model? The protocols and the security arguments are recast in the most efficient pairing setting, i. This forms the basis of the corresponding notions for identity-based encryption schemes. In contrast to Ohrimenko et al. Available dedicated constructions could achieve selective security under parameterized assumption.

So, a natural goal is to obtain schemes which can be proved secure in this model under the assumption that some computational problem is hard to solve. The work of Boneh and Franklin caught immediate attention of the crypto community and spurred further research in this area. The atmosphere, as a dynamical system, exhibits chaotic properties. Broadly speaking, both these models allow the adversary to commit to a set of identities and in the challenge phase choose any one of the previously committed identities. In this work, we investigate the so-called nearby friend problem. Going through several stages of simplifications, we finally obtain a simple scheme whose security can be based on two standard assumptions and a natural and minimal extension of the decision Diffie-Hellman problem for asymmetric pairing groups. For these reasons, it is believed that some of these protocols cannot be implemented with Type 3 pairings, while for some the security reductions either cannot be transformed to the Type 3 setting or else require a stronger complexity assumption.

Our construction is proven secure in the standard model without random oracles. The schemes beat the known lower bounds in the Type 3 setting and thereby establish that the Type 2 setting permits construction of cryptographic schemes with unique properties not achievable in Type 3. The only previous construction in the same setting is due to Waters. Multiple forking has turned out to be a useful tool in the security argument of several cryptographic protocols. Professionals who are trying to design an encryption solution will find it to be a good source on the underlying mathematics. Storing data in untrusted cloud, keeping it confidential and allowing search and other operations on the encrypted data without revealing any meaningful information is currently an area of major interest in cryptology. We demonstrate the effectiveness of the fault attacks on a public-key encryption scheme, an identity-based encryption scheme, and an oblivious transfer protocol when implemented with a symmetric pairing derived from a supersingular elliptic curve with embedding degree 2.