Homomorphic public-key cryptosystems over groups and rings

Dima Grigoriev Ilia V. Ponomarenko Homomorphic public-key cryptosystems over groups and rings http://arxiv.org/abs/cs.CR/0309010 2003 CoRR cs.CR/0309010 db/journals/corr/corr0309.html#cs-CR-0309010 informal publication