Morten Øygarden became the 150th PhD candidate to defend his thesis at Simula this week!
Morten Øygarden and Marianne Aasen, Director of the Simula School of Research and Innovation (Photo: Simula)

Morten Øygarden became the 150th PhD candidate to defend his thesis at Simula this week!


On Monday, September 6th, Morten Øygarden successfully defended his PhD thesis, becoming the 150th PhD candidate to defend his PhD at Simula. Additionally, Øygarden became the first from Simula UiB to defend his PhD thesis in their new offices at Marineholmen in Bergen.

The defence took place atSimula UiB's new offices in Bergen. Simula UiB was established in 2016 and is currently supervising 11 PhD candidates. As a group, Simula has supervised PhD candidates since its beginning in 2001, with the first defence held the year after. So far in 2021, ninecandidates have defended.

Øygarden will continue at Simula UiB as aPostdoctoral Fellow.

Congratulations to Dr. Øygarden and Simula UiB!

About the thesis

Title: "Algebraic Cryptanalysis of Cryptographic Schemes with Extension Field Structure"

Asymmetric cryptography is an essential component for privacy and secure communication over the Internet. In the future, the ciphers in use today may be threatened by a new type of computer based on quantum mechanics. Consequently, many researchers have studied possible variants of quantum-secure cryptography, i.e., asymmetric ciphers that quantum computers cannot break.

One of the main directions within this field is based on the problem of finding a common solution to a system of multivariate polynomials. Several proposed ciphers also use structures over mathematical extension fields in order to be effectively implemented in computer systems.

This dissertation analyzes the security of cryptographic systems that use such extension fields. One of the main findings is that such asymmetric encryption ciphers are not as secure as previously believed and should not be used. The dissertation also studies the use of structure over extension fields within symmetrical ciphers.


  • Professor Øyvind Ytrehus,Research Director Simula UiB
  • Professor Håvard Raddum, Simula UiB

Adjudication committee:

  • Antoine Joux, The CISPA Helmholtz Center for Information Security
  • Magali Bardet, Université de Rouen, Normandie
  • Head of the committee: Professor Kjell Jørgen Hole

Chair of defence:

  • Associate professor Pål Grønås Drange