# Hybrid McEliece

## HyMES

*The Hybrid McEliece Encription Scheme.*

Most of the previous works have been devoted to cryptanalysis and to semantic security but fewer attempts have been made to examine implementation issues.

Implementing a (public key) cryptosystem is a tradeoff between security and efficiency. For that reason, cryptanalysis and implementation have to be considered in unison.

Though the public key size is rather large, the McEliece encryption scheme possesses some strong features. It has a good security reduction and low complexity algorithms for encryption and decryption. As a consequence, it is conceivable, compared with number-theory based cryptosystems, to gain an order of magnitude in performance.

Here, we will describe a slightly modified version of the scheme (which we call * hybrid *). It has two modifications, the first increases the information rate by putting some data in the error pattern. The second reduces the public key size by making use of a generator matrix in row echelon form. We proved the same
security reduction as for the original system holds.

**Please note**, this program is meant to evaluate the system performance. It has all the algorithms implemented. This is a research tool and it should *not* be used as a full fledged encryption scheme. In particular the semantic security layer has not been implemented.