A note on the security of MST 3

In this paper, we study the recently proposed encryption scheme MST 3 , focusing on a concrete instantiation using Suzuki-2-groups. In a passive scenario, we argue that the one wayness of this scheme may not, as claimed, be proven without the assumption that factoring group elements with respect to random covers for a subset of the group is hard. As a result, we conclude that for the proposed Suzuki 2-groups instantiation, impractical key sizes should be used in order to prevent more or less straightforward factorization attacks.