Kristian Gjøsteen

About

Kristian Gjøsteen is a professor at the Department of Mathematical Sciences. He has a MSc and a PhD from NTNU. He belongs to the Algebra Group.

Gjøsteen's research interests include cryptographic voting systems, key exchange protocols, cloud cryptography, formal methods applied to security proofs and privacy. Publication list.

Gjøsteen was a member of the Norwegian Government’s Committee of Digital Vulnerabilities in Society (Lysne-utvalget). He has worked on electronic voting for the Norwegian government (2009-13), as well as electronic identification in Norway.

Publications

2026

Kjørven, Marte Eidsand; Gjøsteen, Kristian; Wærstad, Tone Linn. (2026) Safe and inclusive or unsafe and discriminatory? European digital identity wallets and the challenges of ‘sole control’. Computer Law & Security Review
Academic article

2025

Kjørven, Marte Eidsand; Riisnæs, Rolf; Mahler, Tobias; Gjøsteen, Kristian; Langford, Malcolm; Wærstad, Tone Linn; Omland, Lars Petter Halvorsen. (2025) Helhetlig, trygg og inkluderende digital identitetsforvaltning i Norge: Anbefalinger fra SODI-prosjektet. Universitetet i Oslo
Policy report
Nurnberger, Lea Sibylle; Costache, Anamaria; Gjøsteen, Kristian. (2025) Analysis and Optimisation of Fully Homomorphic Encryption. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis
Millerjord, Lise; Boyd, Colin Alexander; Gjøsteen, Kristian; Gligoroski, Danilo; Mjølsnes, Stig Frode. (2025) Key Exchange in a Post Quantum World. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis

2024

Dragan, Constantin Catalin; Dupressoir, François; Gjøsteen, Kristian; Haines, Thomas; Rønne, Peter B.; Solberg, Morten Rotvold. (2024) Machine-Checked Proofs of Accountability: How to sElect Who is to Blame.
Academic chapter

2023

Fondevik, Elsie Margrethe Staff Mestl; Gjøsteen, Kristian. (2023) Modeling Noise-Accepting Key Exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Fondevik, Elsie Margrethe Staff Mestl; Gjøsteen, Kristian; Millerjord, Lise. (2023) Hybrid Group Key Exchange with Application to Constrained Networks. Lecture Notes in Computer Science (LNCS)
Academic article
Aranha, Diego F.; Baum, Carsten; Gjøsteen, Kristian; Silde, Tjerand Aga. (2023) Verifiable Mix-Nets and Distributed Decryption for Voting from Lattice-Based Assumptions. Proceedings of the ACM Conference on Computer and Communications Security
Academic article
Raikwar, Mayank; Wu, Shuang; Gjøsteen, Kristian. (2023) Security Model for Privacy-Preserving Blockchain-Based Cryptocurrency Systems.
Academic chapter
Gjøsteen, Kristian; Haines, Thomas; Solberg, Morten Rotvold. (2023) Coercion Mitigation for Voting Systems with Trackers: A Selene Case Study.
Academic chapter
Gellert, Kai; Gjøsteen, Kristian; Jacobsen, Håkon; Jager, Tibor. (2023) On Optimal Tightness for Key Exchange with Full Forward Secrecy via Key Confirmation. Lecture Notes in Computer Science (LNCS)
Academic article

2022

Drăgan, Constantin Cătălin; Dupressoir, François; Estaji, Ehsan; Gjøsteen, Kristian; Haines, Thomas; Ryan, Peter Y. A.; Rønne, Peter B.; Solberg, Morten Rotvold. (2022) Machine-Checked Proofs of Privacy Against Malicious Boards for Selene & Co.
Academic chapter
Gjøsteen, Kristian. (2022) Practical Mathematical Cryptography. CRC Press
Textbook
Gjøsteen, Kristian; Raikwar, Mayank; Wu, Shuang. (2022) PriBank: Confidential Blockchain Scaling Using Short Commit-and-Proof NIZK Argument.
Academic chapter
Gjøsteen, Kristian; Haines, Thomas Edmund; Müller, Johannes; Rønne, Peter B.; Silde, Tjerand. (2022) Verifiable Decryption in the Head. Lecture Notes in Computer Science (LNCS)
Academic article

2021

Gjøsteen, Kristian; Haines, Thomas Edmund; Solberg, Morten Rotvold. (2021) Efficient Mixing of Arbitrary Ballots with Everlasting Privacy: How to Verifiably Mix the PPATC Scheme. Lecture Notes in Computer Science (LNCS)
Academic article
Aranha, Diego F.; Baum, Carsten; Gjøsteen, Kristian; Silde, Tjerand; Tunge, Thor. (2021) Lattice-Based Proof of Shuffle and Applications to Electronic Voting. Lecture Notes in Computer Science (LNCS)
Academic article
de Kock, Bor; Gjøsteen, Kristian; Veroni, Mattia. (2021) Practical Isogeny-Based Key-Exchange with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article

2020

Estaji, Ehsan; Haines, Thomas Edmund; Gjøsteen, Kristian; Rønne, Peter; Ryan, Peter Y. A.; Soroush, Najmeh. (2020) Revisiting Practical and Usable Coercion-Resistant Remote E-Voting. Lecture Notes in Computer Science (LNCS)
Academic article
Davies, Gareth Thomas; Galteland, Herman; Gjøsteen, Kristian; Jiang, Yao. (2020) Cloud-assisted Asynchronous Key Transport with Post-Quantum Security. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Jiang, Yao. (2020) Fast and Secure Updatable Encryption. Lecture Notes in Computer Science (LNCS)
Academic article
Rønne, Peter B.; Atashpendar, Arash; Gjøsteen, Kristian; Ryan, Peter Y. A.. (2020) Short Paper: Coercion-Resistant Voting in Linear Time via Fully Homomorphic Encryption: Towards a Quantum-Safe Scheme. Lecture Notes in Computer Science (LNCS)
Academic article

2019

Cohn-Gordon, Katriel; Cremers, Cas; Gjøsteen, Kristian; Jacobsen, Håkon; Jager, Tibor. (2019) Highly Efficient Key Exchange Protocols with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Gjøsteen, Kristian; Gritti, Clementine Jeanne Pierrette; Haines, Thomas Edmund. (2019) A Blind Coupon Mechanism Enabling Veto Voting over Unreliable Networks. Lecture Notes in Computer Science (LNCS)
Academic article
Cremers, Cas; Gjøsteen, Kristian; Jager, Tibor; Cohn-Gordon, Katriel. (2019) Highly Efficient Key Exchange Protocols with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article

2018

Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2018) Security notions for cloud storage and deduplication. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Jiang, Yao. (2018) Offline Assisted Group Key Exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Jager, Tibor. (2018) Practical and tightly-secure digital signatures and authenticated key exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Strand, Martin; Gjøsteen, Kristian; Buan, Aslak Bakke. (2018) Fully homomorphic encryption with applications to electronic voting. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2018) Definitions for plaintext-existence hiding in cloud storage.
Academic chapter

2017

Armknecht, Frederik; Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Toorani, Mohsen. (2017) Side channels in deduplication: trade-offs between leakage and efficiency.
Academic chapter
Galteland, Herman; Gjøsteen, Kristian. (2017) Malware, Encryption, and Rerandomization - Everything is Under Attack. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Strand, Martin. (2017) A Roadmap to Fully Homomorphic Elections: Stronger Security, Better Verifiability.
Academic chapter

2016

Gjøsteen, Kristian; Lund, Anders Smedstuen. (2016) An experiment on the security of the Norwegian electronic voting protocol. Annales des télécommunications
Academic article
Boyd, Colin Alexander; Davies, Gareth T.; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2016) Using Cryptography to Control Your Data at a Distance. ERCIM News
Academic article

2015

Lysne, Olav; Beitland, Kristine; Gjøsteen, Kristian; Hagen, Janne; Jarbekk, Eva; Lunde, Einar; Manne, Fredrik; Nystrøm, Sofie. (2015) Digital sårbarhet – sikkert samfunn. Norwegian Ministry of Justice and Public Security
Academic monograph

2014

Aspnes, James; Diamadi, Zoë; Yampolskiy, Aleksandr; Gjøsteen, Kristian; Peralta, René. (2014) Spreading Alerts Quietly and the Subgroup Escape Problem. Journal of Cryptology
Academic article

2012

Gjøsteen, Kristian; Thuen, Øystein Øvreås. (2012) Password-Based Signatures.
Academic chapter

2011

Gjøsteen, Kristian; Petrides, George; Steine, Asgeir Bertelsen. (2011) A Novel Framework for Protocol Analysis. Lecture Notes in Computer Science (LNCS)
Academic article
Thuen, Øystein Øvreås; Gjøsteen, Kristian. (2011) Bilinear Pairings in Cryptography. NTNU
Doctoral thesis

2010

Gjøsteen, Kristian; Steine, Asgeir; Petrides, George. (2010) Formal verification of reductions in cryptography.
Academic chapter

2008

Gjøsteen, Kristian. (2008) A Latency-Free Election Scheme. Lecture Notes in Computer Science (LNCS)
Academic article
Andova, Suzana; Cremers, Cas; Gjøsteen, Kristian; Mauw, Sjouke; Mjølsnes, Stig Frode; Radomirovic, Sasa. (2008) A framework for compositional verification of security protocols. Information and Computation
Academic article
Gjøsteen, Kristian. (2008) Weaknesses in BankID, a Norwegian PKI substitute deployed by Norwegian banks. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Kråkmo, Lillian. (2008) Round-Optimal Blind Signatures from Waters Signatures. Lecture Notes in Computer Science (LNCS)
Academic article

2007

Gjøsteen, Kristian; Kråkmo, Lillian. (2007) Universally Composable Signcryption. Lecture Notes in Computer Science (LNCS)
Academic article
Brown, Daniel R. L.; Gjøsteen, Kristian. (2007) A Security Analysis of the NIST SP 800-90 Elliptic Curve Random Number Generator. Lecture Notes in Computer Science (LNCS)
Academic article

2006

Gjøsteen, Kristian. (2006) A new security proof for Damgard's ElGamal. Lecture Notes in Computer Science (LNCS)
Academic article

2005

Gjøsteen, Kristian. (2005) Homomorphic Cryptosystems Based on Subgroup Membership Problems. Lecture Notes in Computer Science (LNCS)
Academic article
Aspnes, James; Diamadi, Zoë; Gjøsteen, Kristian; Peralta, René; Yampolskiy, Aleksandr. (2005) Spreading Alerts Quietly and the Subgroup Escape Problem. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2005) Security Notions for Disk Encryption. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2005) Symmetric Subgroup Membership Problems. Lecture Notes in Computer Science (LNCS)
Academic article

Journal publications

Kjørven, Marte Eidsand; Gjøsteen, Kristian; Wærstad, Tone Linn. (2026) Safe and inclusive or unsafe and discriminatory? European digital identity wallets and the challenges of ‘sole control’. Computer Law & Security Review
Academic article
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2018) Security notions for cloud storage and deduplication. Lecture Notes in Computer Science (LNCS)
Academic article
Fondevik, Elsie Margrethe Staff Mestl; Gjøsteen, Kristian. (2023) Modeling Noise-Accepting Key Exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Fondevik, Elsie Margrethe Staff Mestl; Gjøsteen, Kristian; Millerjord, Lise. (2023) Hybrid Group Key Exchange with Application to Constrained Networks. Lecture Notes in Computer Science (LNCS)
Academic article
Cohn-Gordon, Katriel; Cremers, Cas; Gjøsteen, Kristian; Jacobsen, Håkon; Jager, Tibor. (2019) Highly Efficient Key Exchange Protocols with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Jiang, Yao. (2018) Offline Assisted Group Key Exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2008) A Latency-Free Election Scheme. Lecture Notes in Computer Science (LNCS)
Academic article
Aranha, Diego F.; Baum, Carsten; Gjøsteen, Kristian; Silde, Tjerand Aga. (2023) Verifiable Mix-Nets and Distributed Decryption for Voting from Lattice-Based Assumptions. Proceedings of the ACM Conference on Computer and Communications Security
Academic article
Andova, Suzana; Cremers, Cas; Gjøsteen, Kristian; Mauw, Sjouke; Mjølsnes, Stig Frode; Radomirovic, Sasa. (2008) A framework for compositional verification of security protocols. Information and Computation
Academic article
Gjøsteen, Kristian; Petrides, George; Steine, Asgeir Bertelsen. (2011) A Novel Framework for Protocol Analysis. Lecture Notes in Computer Science (LNCS)
Academic article
Estaji, Ehsan; Haines, Thomas Edmund; Gjøsteen, Kristian; Rønne, Peter; Ryan, Peter Y. A.; Soroush, Najmeh. (2020) Revisiting Practical and Usable Coercion-Resistant Remote E-Voting. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2005) Homomorphic Cryptosystems Based on Subgroup Membership Problems. Lecture Notes in Computer Science (LNCS)
Academic article
Aspnes, James; Diamadi, Zoë; Gjøsteen, Kristian; Peralta, René; Yampolskiy, Aleksandr. (2005) Spreading Alerts Quietly and the Subgroup Escape Problem. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Lund, Anders Smedstuen. (2016) An experiment on the security of the Norwegian electronic voting protocol. Annales des télécommunications
Academic article
Davies, Gareth Thomas; Galteland, Herman; Gjøsteen, Kristian; Jiang, Yao. (2020) Cloud-assisted Asynchronous Key Transport with Post-Quantum Security. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Gjøsteen, Kristian; Gritti, Clementine Jeanne Pierrette; Haines, Thomas Edmund. (2019) A Blind Coupon Mechanism Enabling Veto Voting over Unreliable Networks. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2005) Security Notions for Disk Encryption. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2005) Symmetric Subgroup Membership Problems. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Jiang, Yao. (2020) Fast and Secure Updatable Encryption. Lecture Notes in Computer Science (LNCS)
Academic article
Aspnes, James; Diamadi, Zoë; Yampolskiy, Aleksandr; Gjøsteen, Kristian; Peralta, René. (2014) Spreading Alerts Quietly and the Subgroup Escape Problem. Journal of Cryptology
Academic article
Gjøsteen, Kristian; Kråkmo, Lillian. (2007) Universally Composable Signcryption. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Jager, Tibor. (2018) Practical and tightly-secure digital signatures and authenticated key exchange. Lecture Notes in Computer Science (LNCS)
Academic article
Brown, Daniel R. L.; Gjøsteen, Kristian. (2007) A Security Analysis of the NIST SP 800-90 Elliptic Curve Random Number Generator. Lecture Notes in Computer Science (LNCS)
Academic article
Galteland, Herman; Gjøsteen, Kristian. (2017) Malware, Encryption, and Rerandomization - Everything is Under Attack. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2008) Weaknesses in BankID, a Norwegian PKI substitute deployed by Norwegian banks. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Haines, Thomas Edmund; Müller, Johannes; Rønne, Peter B.; Silde, Tjerand. (2022) Verifiable Decryption in the Head. Lecture Notes in Computer Science (LNCS)
Academic article
Rønne, Peter B.; Atashpendar, Arash; Gjøsteen, Kristian; Ryan, Peter Y. A.. (2020) Short Paper: Coercion-Resistant Voting in Linear Time via Fully Homomorphic Encryption: Towards a Quantum-Safe Scheme. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian. (2006) A new security proof for Damgard's ElGamal. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Haines, Thomas Edmund; Solberg, Morten Rotvold. (2021) Efficient Mixing of Arbitrary Ballots with Everlasting Privacy: How to Verifiably Mix the PPATC Scheme. Lecture Notes in Computer Science (LNCS)
Academic article
Aranha, Diego F.; Baum, Carsten; Gjøsteen, Kristian; Silde, Tjerand; Tunge, Thor. (2021) Lattice-Based Proof of Shuffle and Applications to Electronic Voting. Lecture Notes in Computer Science (LNCS)
Academic article
Gjøsteen, Kristian; Kråkmo, Lillian. (2008) Round-Optimal Blind Signatures from Waters Signatures. Lecture Notes in Computer Science (LNCS)
Academic article
Cremers, Cas; Gjøsteen, Kristian; Jager, Tibor; Cohn-Gordon, Katriel. (2019) Highly Efficient Key Exchange Protocols with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article
Gellert, Kai; Gjøsteen, Kristian; Jacobsen, Håkon; Jager, Tibor. (2023) On Optimal Tightness for Key Exchange with Full Forward Secrecy via Key Confirmation. Lecture Notes in Computer Science (LNCS)
Academic article
de Kock, Bor; Gjøsteen, Kristian; Veroni, Mattia. (2021) Practical Isogeny-Based Key-Exchange with Optimal Tightness. Lecture Notes in Computer Science (LNCS)
Academic article
Boyd, Colin Alexander; Davies, Gareth T.; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2016) Using Cryptography to Control Your Data at a Distance. ERCIM News
Academic article

Books

Lysne, Olav; Beitland, Kristine; Gjøsteen, Kristian; Hagen, Janne; Jarbekk, Eva; Lunde, Einar; Manne, Fredrik; Nystrøm, Sofie. (2015) Digital sårbarhet – sikkert samfunn. Norwegian Ministry of Justice and Public Security
Academic monograph
Gjøsteen, Kristian. (2022) Practical Mathematical Cryptography. CRC Press
Textbook

Part of book/report

Drăgan, Constantin Cătălin; Dupressoir, François; Estaji, Ehsan; Gjøsteen, Kristian; Haines, Thomas; Ryan, Peter Y. A.; Rønne, Peter B.; Solberg, Morten Rotvold. (2022) Machine-Checked Proofs of Privacy Against Malicious Boards for Selene & Co.
Academic chapter
Raikwar, Mayank; Wu, Shuang; Gjøsteen, Kristian. (2023) Security Model for Privacy-Preserving Blockchain-Based Cryptocurrency Systems.
Academic chapter
Gjøsteen, Kristian; Steine, Asgeir; Petrides, George. (2010) Formal verification of reductions in cryptography.
Academic chapter
Gjøsteen, Kristian; Thuen, Øystein Øvreås. (2012) Password-Based Signatures.
Academic chapter
Gjøsteen, Kristian; Haines, Thomas; Solberg, Morten Rotvold. (2023) Coercion Mitigation for Voting Systems with Trackers: A Selene Case Study.
Academic chapter
Gjøsteen, Kristian; Raikwar, Mayank; Wu, Shuang. (2022) PriBank: Confidential Blockchain Scaling Using Short Commit-and-Proof NIZK Argument.
Academic chapter
Dragan, Constantin Catalin; Dupressoir, François; Gjøsteen, Kristian; Haines, Thomas; Rønne, Peter B.; Solberg, Morten Rotvold. (2024) Machine-Checked Proofs of Accountability: How to sElect Who is to Blame.
Academic chapter
Armknecht, Frederik; Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Toorani, Mohsen. (2017) Side channels in deduplication: trade-offs between leakage and efficiency.
Academic chapter
Gjøsteen, Kristian; Strand, Martin. (2017) A Roadmap to Fully Homomorphic Elections: Stronger Security, Better Verifiability.
Academic chapter
Boyd, Colin Alexander; Davies, Gareth Thomas; Gjøsteen, Kristian; Raddum, Håvard; Toorani, Mohsen. (2018) Definitions for plaintext-existence hiding in cloud storage.
Academic chapter

Report

Kjørven, Marte Eidsand; Riisnæs, Rolf; Mahler, Tobias; Gjøsteen, Kristian; Langford, Malcolm; Wærstad, Tone Linn; Omland, Lars Petter Halvorsen. (2025) Helhetlig, trygg og inkluderende digital identitetsforvaltning i Norge: Anbefalinger fra SODI-prosjektet. Universitetet i Oslo
Policy report

Student thesis or dissertation

Nurnberger, Lea Sibylle; Costache, Anamaria; Gjøsteen, Kristian. (2025) Analysis and Optimisation of Fully Homomorphic Encryption. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis
Millerjord, Lise; Boyd, Colin Alexander; Gjøsteen, Kristian; Gligoroski, Danilo; Mjølsnes, Stig Frode. (2025) Key Exchange in a Post Quantum World. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis
Thuen, Øystein Øvreås; Gjøsteen, Kristian. (2011) Bilinear Pairings in Cryptography. NTNU
Doctoral thesis
Strand, Martin; Gjøsteen, Kristian; Buan, Aslak Bakke. (2018) Fully homomorphic encryption with applications to electronic voting. Norges teknisk-naturvitenskapelige universitet
Doctoral thesis

Teaching

Courses

Outreach