Ayoub Otmani Jean-Pierre Tillich Léonard Dallot Cryptanalysis of Two McEliece Cryptosystems Based on Quasi-Cyclic Codes http://arxiv.org/abs/0804.0409 2008 CoRR abs/0804.0409 db/journals/corr/corr0804.html#abs-0804-0409 informal publication