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We show that the structure of the problem is directly linked to the
structure of quadratic forms in odd and even characteristic. We describe a completely new method allowing to efficiently solve most instances. Unlike previous solving techniques, this is not based upon Gröbner basis computations.
In this article we give a new framework for cubes that are useful in the cryptanalytic context. In addition, we show how algebraic modelling of a cipher can greatly be improved when taking both cubes and linear equivalences between variables into account. When taking many instances of Trivium, we empirically show a saturation effect, i.e., the number of variables to model an attack will become constant for a given number of rounds. Moreover, we show how to systematically find cubes both for general primitives and also specifically for Trivium. For the latter, we have found all cubes up to round 446 and draw some conclusions on their evolution between rounds. All techniques in this article are general and can be applied to any cipher.
In this paper, we present an augmented model of both LROM and some leakage models. In our new model, both the secret key and pairs of input and output of hash functions can be leaked. Furthermore, the secret key can be leaked continually during the whole lifecycle of a cryptographic scheme. Hence, our new model is more universal and stronger than LROM and some leakage models (e.g. only computation leaks model and bounded memory leakage model). As an application example, we also present a public key encryption scheme which is provably IND-CCA secure in our new model.
(IBE) from the standard assumptions where the security loss depends
only on the security parameter and is independent of the number of
secret key queries. This partially answers an open problem posed by
Waters (Eurocrypt 2005). Our construction combines Waters\' dual
system encryption methodology (Crypto 2009) with the Naor-Reingold
pseudo-random function (J. ACM, 2004) in a novel way. The security
of our scheme relies on the DLIN assumption in prime-order groups.
the specific needs of certain application e.g., a vehicular adhoc network (VANET). Groth GS is the first efficient GS scheme in the BSZ-model with security proofs in the standard model. We modify the Groth GS in order to meet a restricted, but arguably sufficient set of privacy proper-ties. Although there are some authentication schemes using GS none of them satisfy all the desirable security and privacy properties. Either they follow GSs that rely on Random Oracle Model, or unable to satisfy potential application requirements. In particular, link management which allows any designated entities to link messages, whether they are coming from the same member or a certain group of members without revealing their identities; opening soundness that prevents malicious accusations by the opener against some honest member of the group; revocation system that privileges from fraudulent member like the traditional Public Key infrastructure (PKI). In order to achieve the aforementioned security properties together, we propose a new GS model where linkability, sound
opening and revocability properties are assembled in a single scheme. The novelty of our proposal stems from extending the Groth GS by relaxing strong privacy properties to a scheme with a lightly lesser privacy in order to fit an existing VANET application requirements. In addition, we partially minimize the Groth GS scheme to expedite efficiency.
interests at industry due to their vast applications such as supply chain, access control, inventory, transport, health care and home appliances. Although tag identification is the primary security goal of an RFID system, privacy issue is equally, even more, important concern in RFID system because of pervasiveness of RFID tags. Over the years, many protocols have been proposed for RFID tags\' identification using different cryptographic primitives. It has been observed that most of them provide tags\' identification, but they fail to preserve tags\' privacy. It has been also proven that public-key primitives are essential for strong privacy and security
requirements in RFID systems. In this paper, we present a mutual authentication protocol for RFID systems using elliptic curves arithmetic.
Precisely, the proposed protocol provides narrow-strong and wide-weak
privacy and resists tracking attacks under standard complexity assumption. The protocol is compared with related works and found efficient in comparison to others.