Key Length Estimates - Practical and Theoretical Optimizations and Modern Approaches on NFS Instances for Accurate Costs
ANR (2022-2026)

Research project funded by the french Agence Nationale de la Recherche (2022-2026).


  • INRIA Nancy / LORIA
  • LIP6
  • Beginning and duration of the scientific project: January 2022 - 48 Months
  • Project coordinator: Emmanuel Thomé
  • Lip6 local coordinator: Charles Bouillaguet

Project Summary

The RSA cryptosystem and the Diffie-Hellman key exchange protocol in finite fields were the first invented primitives of public-key cryptography.

It is hard to estimate the time and resources that are needed to factor an integer, and thereby how hard it is to break RSA. All regulatory bodies recommend that people either avoid RSA, or prefer large RSA key sizes for safety, above 2048 bits at least. In environments where computing power is plentiful, this recommendation is most often followed. Yet, it is a fact that we do rely on cryptography that uses smaller key sizes.

We plan to employ our expertise to provide solid hardness assessments for key sizes that are relevant today, and for which accuracy in the prediction is important. Our targets for accurate assessment are RSA-1024 and DH-1024 as well as specific discrete logarithm-related problems that arise in the blockchain context. We also intend to develop simulation software that would enable more accurate estimates.

(pictures credit: upklyak / Freepik)