%0 Conference Proceedings %T Improving the Performance of the SYND Stream Cipher %+ Center for Advanced Security Research Darmstadt [Darmstadt] (CASED) %+ Technische Universitat Darmstadt Fachbereich Informatik %+ Laboratoire Hubert Curien (LHC) %A Meziani, Mohammed %A Hoffmann, Gerhard %A Cayrel, Pierre-Louis %< avec comité de lecture %( Africacrypt 2012 %B Africacrypt 2012 %C Morocco %P 99-116 %8 2012-06-01 %D 2012 %Z Computer Science [cs]/Cryptography and Security [cs.CR]Conference papers %X . In 2007, Gaborit et al. proposed the stream cipher SYND as an improvement of the pseudo random number generator due to Fischer and Stern. This work shows how to improve considerably the e ciency the SYND cipher without using the so-called regular encoding and without compromising the security of the modi ed SYND stream cipher. Our proposal, called XSYND, uses a generic state transformation which is reducible to the Regular Syndrome Decoding problem (RSD), but has better computational characteristics than the regular encoding. A rst implementation shows that XSYND runs much faster than SYND for a comparative security level (being more than three times faster for a security level of 128 bits, and more than 6 times faster for 400-bit security), though it is still only half as fast as AES in counter mode. Parallel computation may yet improve the speed of our proposal, and we leave it as future research to improve the e ciency of our implementation. %G English %2 https://ujm.hal.science/ujm-00865533/document %2 https://ujm.hal.science/ujm-00865533/file/2012_-_Improving_the_performance_of_the_SYND_Stream-Cipher.pdf %L ujm-00865533 %U https://ujm.hal.science/ujm-00865533 %~ UNIV-ST-ETIENNE %~ IOGS %~ CNRS %~ LAHC %~ PARISTECH %~ UDL