  This paper studies a variant of the McEliece cryptosystem able to ensure that
the code used as the public key is no longer permutation-equivalent to the
secret code. This increases the security level of the public key, thus opening
the way for reconsidering the adoption of classical families of codes, like
Reed-Solomon codes, that have been longly excluded from the McEliece
cryptosystem for security reasons. It is well known that codes of these classes
are able to yield a reduction in the key size or, equivalently, an increased
level of security against information set decoding; so, these are the main
advantages of the proposed solution. We also describe possible vulnerabilities
and attacks related to the considered system, and show what design choices are
best suited to avoid them.
