Timing Attacks against the Syndrome Inversion in Code-Based Cryptosystems

In this work we present new timing vulnerabilities that arise in the inversion of the error syndrome through the Extended Euclidean Algorithm that is part of the decryption operation of code-based Cryptosystems. We analyze three types of timing attack vulnerabilities theoretically and experimentally: The first allows recovery of the zero-element of the secret support, the second is a refinement of a previously described vulnerability yielding linear equations about the secret support, and the third enables to retrieve non-linear equations about the secret support. Furthermore, we analyze theoretically the limitations applying to actual attacks based on the information gained in such manner.