Akinori Kawachi Keisuke Tanaka Keita Xagawa Multi-bit Cryptosystems Based on Lattice Problems. 315-329 2007 conf/pkc/2007 Public Key Cryptography http://dx.doi.org/10.1007/978-3-540-71677-8_21 db/conf/pkc/pkc2007.html#KawachiTX07