Modul: MAT076 Arbeitsgemeinschaft in Codierungstheorie und Kryptographie

## eSeminar: EHT public-key crypto-system and digital signatures

Talk by Prof. Dr. Igor Semaev

**Date:** 05.05.21 **Time:** 15.00 - 16.00 **Room:**

(**This eSeminar will take place on Zoom, using the same meeting details as previous seminars. If you do not have meeting details, please contact simran.tinani@math.uzh.ch **)

Two works will be surveyed: "New Public-Key Crypto-System EHT" (A.Budroni, I.Semaev) and "EHT Digital Signature Algorithm" (I.Semaev).
The LWE (Learning with Errors) problem was introduced by Regev in 2005, where an LWE based public-key encryption was described. The problem was there proved to be hard assuming the hardness of computing shortest non-zero vectors in general lattices. Since then several lattice-based public-key crypto-systems were invented. The NIST Post-Quantum Standardisation Process stimulated interest in developing new quantum computer resistant public-key protocols. A number of submissions to this competition are LWE or Ring LWE based.
In the first work, an LWE problem with a hidden trapdoor is introduced. It is used to construct a new efficient public-key crypto-system EHT. The new system may be used as a KEM (Key Encapsulating Mechanism) too. It is significantly different from LWE based NIST public-key encryption candidates, e.g., FrodoKEM. The performance of EHT compares favourably with FrodoKEM.
In the second work, a similar idea is used to construct a new digital signature algorithm. It is significantly different from NIST digital signature candidates. Forging EHT signatures may be reduced to solving Closest Vector Problem for a specific lattice with a small approximation factor. The parameters of the new system are comparable to those of the NIST candidates.