A real life project in cryptography: Assessment of RSA keys

We describe a project carried out by CryptoLabTN. In this project we provide a rigorous analysis of the RSA cryptographic keys employed in the Certification Authority (CA) to certify the keys exchange during some financial transactions. In particular, we consider the asymptotically fastest known factorization algorithm, that is, the General Number Field Sieve (GNFS). We estimate the computational effort required by an attacker to break the certification keys. Our estimate differs from a direct application of the asymptotic estimates,because in a real-life attack several factors have to be vetted.