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Framework to Integrate Post-quantum Key Exchanges into Internet Key Exchange Protocol Version 2 (IKEv2)

Scott R. Fluhrer, Cen Jung Tjhai, Óscar García-Morchón, Mark Tomlinson, Valery Smyslov, Daniel Van Geest

Published Jul 9, 2019• 10 citations
OpenAlex

Abstract

This document describes how to extend Internet Key Exchange Protocol Version 2 (IKEv2) so that the shared secret exchanged between peers has resistance against quantum computer attacks. The basic idea is to exchange one or more post-quantum key exchange payloads in conjunction with the existing (Elliptic Curve) Diffie-Hellman payload.

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A Virtual Private Network (VPN) ensures the confidentiality and integrity of data transferred between two endpoints, even if the means of transport are insecure. One popular protocol is Internet Protocol Security (IPSec) which operates at OSI layer 3 and protects all protocols at higher layers. Cryptographic keys in IPSec are negotiated using the Internet Key Exchange (IKE) protocol. IKE negotiates security parameters for IPSec sessions. In particular, the IKEv2 protocol uses the Elliptic Curve Diffie-Hellman (ECDH) algorithm to establish a secret key shared between two nodes on a network. Although solving such a problem remains difficult with current computing power, it is believed that generic quantum computers will be able to solve this problem, which implies that the security of IKEv2 is compromised. There are, however, several cryptographic systems that are trusted to be resistant to attacks by quantum computers. This family of cryptosystems is known as quantum-resistant cryptography (QRC). In this paper, after highlighting the requirements for a secure key exchange protocol, we briefly review the QRC solutions that have been proposed in the recent literature.

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The recent advances in the development of quantum computers pose a threat to the cryptography used today. While symmetric algorithms can adapt to those challenges, no prevalent key exchange method can protect against quantum computer based attacks. There already exist several new, quantum-resistant approaches. Yet, all of them either lack in confidence regarding their security or require large data to be transmitted. Due to the lack of confidence in these algorithms, researchers tend towards hybrid key exchange methods which combine at least two different algorithms. As long as one of them prevails, the shared secret remains secure. Yet, these hybrid key exchanges together with algorithms which transmit large payloads require significant changes to the design of security protocols. IKEv2 is willing to introduce radical changes in order to support as many different algorithms as possible. This was expected to impact the protocol's operational feasibility, but remained to be tested due to the lack of a working reference implementation of the newly proposed internet drafts. To address this issue, we implemented these drafts using a modified version of the OpenIKED as basis that already comprised the first steps towards the concept's integration. During the implementation we found that several design choices severely hinder a clean and maintainable structure. With the resulting implementation, we tested the adjusted protocol under real-world conditions. The results show that the result generally works but struggles to cope with slow, lossy networks. Based on these insights, we drafted an improved protocol design which also supports the full range of quantum-resistant key exchange methods. In contrast to the current drafts, it promises a cheaper and more maintainable implementation.

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The Internet Key Exchange Protocol Version 2 (IKEv2) underpins Internet Protocol Security (IPsec) by establishing secure associations and negotiating cryptographic keys. Its reliance on classical public-key primitives such as Elliptic Curve Diffie–Hellman (ECDH) renders it vulnerable to quantum attacks, as Shor’s algorithm can break these schemes once large-scale quantum computers become available. To address this challenge, we integrate post-quantum cryptography into IKEv2 using a hybrid key exchange combining ECDH over P-384 with the ML-KEM-768 parameter set of the Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM), following Request for Comments (RFC) 9370 and RFC 9242. We present a Fragmentation Boundary Model that identifies when post-quantum payloads approach or exceed the non-fragmenting IKE_SA_INIT payload budget across ML-KEM parameter sets, Internet Protocol (IP) versions, and effective path maximum transmission units (PMTUs). We implemented the hybrid design on a Texas Instruments TM4C1294 microcontroller running FreeRTOS and CycloneTCP, and measured its execution time, memory footprint, and network overhead. Across 150 successful handshakes per configuration, mean Security Association establishment time increased from 3390.4 to 3488.6 ms, an overhead of 98.2 ms (2.9%). Flash use increased by 8%, random-access memory (RAM) use by 5%, and total IKEv2 traffic size by 42%, while no IP fragmentation was observed under the evaluated Internet Protocol version 4 (IPv4) conditions. These findings establish the feasibility of the evaluated hybrid configuration on the TM4C1294 platform and provide a platform-specific baseline for further evaluation of quantum-resilient IPsec on embedded automotive architectures.

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The goal of this project is to understand and analyze the supersingular isogeny Diffie Hellman (SIDH), a post-quantum key exchange protocol which security lies on the isogeny-finding problem between supersingular elliptic curves. In order to do so, we first introduce the reader to cryptography focusing on key agreement protocols and motivate the rise of post-quantum cryptography as a necessity with the existence of the model of quantum computation. We review some of the known attacks on the SIDH and finally study some algorithmic aspects to understand how the protocol can be implemented.

•Jan 1, 2020•0 citations
This document describes how to extend Internet Key Exchange Protocol
Version 2 (IKEv2) so that the shared secret exchanged between peers
has resistance against quantum computer attacks. The basic idea is to
exchange one or more post-quantum key exchange payloads in conjunction
with the existing (Elliptic Curve) Diffie-Hellman payload.
A Virtual Private Network (VPN) ensures the confidentiality and integrity of data transferred between two endpoints, even if the means of transport are insecure. One popular protocol is Internet Protocol Security (IPSec) which operates at OSI layer 3 and protects all protocols at higher layers. Cryptographic keys in IPSec are negotiated using the Internet Key Exchange (IKE) protocol. IKE negotiates security parameters for IPSec sessions. In particular, the IKEv2 protocol uses the Elliptic Curve Diffie-Hellman (ECDH) algorithm to establish a secret key shared between two nodes on a network. Although solving such a problem remains difficult with current computing power, it is believed that generic quantum computers will be able to solve this problem, which implies that the security of IKEv2 is compromised. There are, however, several cryptographic systems that are trusted to be resistant to attacks by quantum computers. This family of cryptosystems is known as quantum-resistant cryptography (QRC). In this paper, after highlighting the requirements for a secure key exchange protocol, we briefly review the QRC solutions that have been proposed in the recent literature.
The recent advances in the development of quantum computers pose a threat to the cryptography used today. While symmetric algorithms can adapt to those challenges, no prevalent key exchange method can protect against quantum computer based attacks. There already exist several new, quantum-resistant approaches. Yet, all of them either lack in confidence regarding their security or require large data to be transmitted. Due to the lack of confidence in these algorithms, researchers tend towards hybrid key exchange methods which combine at least two different algorithms. As long as one of them prevails, the shared secret remains secure. Yet, these hybrid key exchanges together with algorithms which transmit large payloads require significant changes to the design of security protocols. IKEv2 is willing to introduce radical changes in order to support as many different algorithms as possible. This was expected to impact the protocol's operational feasibility, but remained to be tested due to the lack of a working reference implementation of the newly proposed internet drafts. To address this issue, we implemented these drafts using a modified version of the OpenIKED as basis that already comprised the first steps towards the concept's integration. During the implementation we found that several design choices severely hinder a clean and maintainable structure. With the resulting implementation, we tested the adjusted protocol under real-world conditions. The results show that the result generally works but struggles to cope with slow, lossy networks. Based on these insights, we drafted an improved protocol design which also supports the full range of quantum-resistant key exchange methods. In contrast to the current drafts, it promises a cheaper and more maintainable implementation.
The Internet Key Exchange Protocol Version 2 (IKEv2) underpins Internet Protocol Security (IPsec) by establishing secure associations and negotiating cryptographic keys. Its reliance on classical public-key primitives such as Elliptic Curve Diffie–Hellman (ECDH) renders it vulnerable to quantum attacks, as Shor’s algorithm can break these schemes once large-scale quantum computers become available. To address this challenge, we integrate post-quantum cryptography into IKEv2 using a hybrid key exchange combining ECDH over P-384 with the ML-KEM-768 parameter set of the Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM), following Request for Comments (RFC) 9370 and RFC 9242. We present a Fragmentation Boundary Model that identifies when post-quantum payloads approach or exceed the non-fragmenting IKE_SA_INIT payload budget across ML-KEM parameter sets, Internet Protocol (IP) versions, and effective path maximum transmission units (PMTUs). We implemented the hybrid design on a Texas Instruments TM4C1294 microcontroller running FreeRTOS and CycloneTCP, and measured its execution time, memory footprint, and network overhead. Across 150 successful handshakes per configuration, mean Security Association establishment time increased from 3390.4 to 3488.6 ms, an overhead of 98.2 ms (2.9%). Flash use increased by 8%, random-access memory (RAM) use by 5%, and total IKEv2 traffic size by 42%, while no IP fragmentation was observed under the evaluated Internet Protocol version 4 (IPv4) conditions. These findings establish the feasibility of the evaluated hybrid configuration on the TM4C1294 platform and provide a platform-specific baseline for further evaluation of quantum-resilient IPsec on embedded automotive architectures.
The possibility of quantum computers poses a serious challenge to cryptographic algorithms deployed widely today. IKEv2 is one example of a cryptosystem that could be broken; someone storing VPN communications today could decrypt them at a later time when a quantum computer is available. It is anticipated that IKEv2 will be extended to support quantum-secure key exchange algorithms; however that is not likely to happen in the near term. To address this problem before then, this document describes an extension of IKEv2 to allow it to be resistant to a quantum computer, by using preshared keys.
The possibility of quantum computers poses a serious challenge to cryptographic algorithms deployed widely today. IKEv2 is one example of a cryptosystem that could be broken; someone storing VPN communications today could decrypt them at a later time when a quantum computer is available. It is anticipated that IKEv2 will be extended to support quantum-secure key exchange algorithms; however that is not likely to happen in the near term. To address this problem before then, this document describes an extension of IKEv2 to allow it to be resistant to a quantum computer, by using preshared keys.
The goal of this project is to understand and analyze the supersingular isogeny Diffie Hellman (SIDH), a post-quantum key exchange protocol which security lies on the isogeny-finding problem between supersingular elliptic curves. In order to do so, we first introduce the reader to cryptography focusing on key agreement protocols and motivate the rise of post-quantum cryptography as a necessity with the existence of the model of quantum computation. We review some of the known attacks on the SIDH and finally study some algorithmic aspects to understand how the protocol can be implemented.