Vladimir Shpilrain Alexander Ushakov The Conjugacy Search Problem in Public Key Cryptography: Unnecessary and Insufficient. 285-289 2006 17 Appl. Algebra Eng. Commun. Comput. 3-4 http://dx.doi.org/10.1007/s00200-006-0009-6 db/journals/aaecc/aaecc17.html#ShpilrainU06