@inproceedings {nunez2016nuevas, title = {Nuevas nociones de seguridad y transformaciones gen{\'e}ricas para criptosistemas de recifrado delegado}, booktitle = {XIV Reuni{\'o}n Espa{\~n}ola sobre Criptolog{\'\i}a y Seguridad de la Informaci{\'o}n}, year = {2016}, month = {10/2016}, pages = {174-179}, address = {Mah{\'o}n, Menorca, Islas Baleares}, abstract = {

El recifrado delegado (proxy re-encryption) es un tipo de cifrado de clave p{\'u}blica que permite delegar la capacidad de transformar textos cifrados de una clave p{\'u}blica a otra, sin que se pueda obtener ninguna informaci{\'o}n sobre el mensaje subyacente. Por este motivo, representa un candidato natural para construir mecanismos criptogr{\'a}ficos de control de acceso. En este art{\'\i}culo estudiamos algunos de los problemas de seguridad de este tipo de criptosistemas. En primer lugar, examinamos las nociones de seguridad e identificamos una nueva familia param{\'e}trica de modelos de ataque, que considera la disponibilidad tanto del or{\'a}culo de descifrado como de recifrado. En segundo lugar, estudiamos la aplicabilidad de transformaciones gen{\'e}ricas para mejorar la seguridad, centr{\'a}ndonos en la transformaci{\'o}n Fujisaki-Okamoto, y formulamos las condiciones que nos permiten aplicarla.

}, keywords = {proxy re-encryption}, isbn = { 978-84-608-9470-4}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} } @inproceedings {nunez2015ntrureencrypt, title = {NTRUReEncrypt: An Efficient Proxy Re-Encryption Scheme Based on NTRU}, booktitle = {10th ACM Symposium on Information, Computer and Communications Security (AsiaCCS)}, year = {2015}, month = {04/2015}, pages = {179-189}, abstract = {

The use of alternative foundations for constructing more secure and efficient cryptographic schemes is a topic worth exploring. In the case of proxy re-encryption, the vast majority of schemes are based on number theoretic problems such as the discrete logarithm. In this paper we present NTRUReEncrypt, a new bidirectional and multihop proxy re-encryption scheme based on NTRU, a widely known lattice-based cryptosystem. We provide two versions of our scheme: the first one is based on the conventional NTRU encryption scheme and, although it lacks a security proof, remains as efficient as its predecessor; the second one is based on a variant of NTRU proposed by Stehl{\'e} and Steinfeld, which is proven CPA-secure under the hardness of the Ring-LWE problem. To the best of our knowledge, our proposals are the first proxy re-encryption schemes to be based on the NTRU primitive. In addition, we provide experimental results to show the efficiency of our proposal, as well as a comparison with previous proxy re-encryption schemes, which confirms that our first scheme outperforms the rest by an order of magnitude.

}, isbn = {978-1-4503-3245-3}, doi = {10.1145/2714576.2714585}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} }