2010
Autores
Barbosa, M; Farshim, P;
Publicação
INFORMATION SECURITY AND PRIVACY
Abstract
Completely non-malleable encryption schemes resist attacks which allow an adversary to tamper with both ciphertexts and public keys. In this paper we introduce two extractor-based properties that allow us to gain insight into the design of such schemes and to go beyond known feasibility results in this area. We formalise strong plaintext awareness and secret key awareness and prove their suitability in realising these goals. Strong plaintext awareness imposes that it is infeasible to construct a ciphertext under any public key without knowing the underlying message. Secret key awareness requires it to be infeasible to produce a new public key without knowing a corresponding secret key.
2010
Autores
Barbosa, M; Farshim, P;
Publicação
INFORMATION SECURITY AND PRIVACY
Abstract
We study relations among various notions of complete non-malleability, where an adversary can tamper with both ciphertexts and public-keys, and ciphertext indistinguishability. We follow the pattern of relations previously established for standard non-malleability. To this end, we propose a more convenient and conceptually simpler indistinguishability-based security model to analyse completely non-malleable schemes. Our model is based on strong decryption oracles, which provide decryptions under arbitrarily chosen public keys. We give the first precise definition of a strong decryption oracle, pointing out the subtleties in different approaches that can be taken. We construct the first efficient scheme, which is fully secure against strong chosen-ciphertext attacks, and therefore completely non-malleable, without random oracles.
2009
Autores
Barbosa, M; Farshim, P;
Publicação
PROGRESS IN CRYPTOLOGY - AFRICACRYPT 2009
Abstract
We propose a generic modelling technique that can be used to extend existing frameworks for theoretical security analysis in order to capture the use of timestamps. We apply this technique to two of the most popular models adopted in literature (Bellare-Rogaway and Canetti-Krawczyk). We analyse previous results obtained using these models in light of the proposed extensions, and demonstrate their application to a new class of protocols. In the timed CK model we concentrate on modular design and analysis of protocols, and propose a more efficient timed authenticator relying on timestamps. The structure of this new authenticator implies that an authentication mechanism standardised in ISO-9798 is secure. Finally, we use our timed extension to the BR model to establish the security of an efficient ISO protocol for key transport and unilateral entity authentication.
2008
Autores
Barbosa, M; Brouard, T; Cauchie, S; de Sousa, SM;
Publicação
INFORMATION SECURITY AND PRIVACY
Abstract
We propose a new hybrid protocol for cryptographically secure biometric authentication. The main advantages of the proposed protocol over previous solutions can be summarised as follows: (1) potential for much better accuracy using different types of biometric signals, including behavioural ones; and (2) improved user privacy, since user identities are not transmitted at any point in the protocol execution. The new protocol takes advantage of state-of-the-art identification classifiers, which provide not only better accuracy, but also the possibility to perform authentication without knowing who the user claims to be. Cryptographic security is based on the Paillier public key encryption scheme.
1999
Autores
Farsi, M; Ratcliff, K; Barbosa, M;
Publicação
Computing and Control Engineering Journal
Abstract
CANopen is a truly open protocol that has not been developed by one company alone. Several working groups, consisting of many different device manufacturers and end-users, have co-operated to produce the CANopen standards, now under the supervision of the CAN in Automation organisation. CANopen has been produced as a result of EU funding. This article gives an overview of some of the fundamental concepts of CANopen communication and of CANopen implementation. © IEE: 1999.
2023
Autores
Almeida, JB; Barbosa, M; Barthe, G; Grégoire, B; Laporte, V; Léchenet, JC; Oliveira, T; Pacheco, H; Quaresma, M; Schwabe, P; Séré, A; Strub, PY;
Publicação
IACR Trans. Cryptogr. Hardw. Embed. Syst.
Abstract
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