Different variants of the code-based McEliece cryptosystem were pro- posed to
reduce the size of the public key. All these variants use very structured
codes, which open the door to new attacks exploiting the underlying structure.
In this paper, we show that the dyadic variant can be designed to resist all
known attacks. In light of a new study on list decoding algorithms for binary
Goppa codes, we explain how to increase the security level for given public
keysizes.