The Medium-Field multivariate public key encryption scheme given by Wang et al in the 2006 RSA conference was defeated by the SOLE (second order linearization equation) attack presented by Ding et al. An improved scheme was proposed. The central map of the original scheme was redesigned and the related linear equations can not be calculated by the attacker, and then the new variant can avoid the SOLE attack. Analyses show that the enhanced variant can resist the SOLE attack, Rank attacks, and Gr bner-based method. Therefore it is a more security multivariate public key encryption scheme.
