Network Working Group S. Sheth Internet-Draft Verisign Labs Intended status: Informational T. Chung Expires: 19 April 2026 Virginia Tech B. Overeinder NLnet Labs 16 October 2025 Post-Quantum Cryptography Strategy for DNSSEC draft-sheth-pqc-dnssec-strategy-00 Abstract This document proposes a post-quantum cryptography (PQC) strategy for Domain Name System Security (DNSSEC) that includes two types of algorithms: one or more conservatively designed algorithms that are unlikely ever to need to be replaced, and one or more low-impact drop-in algorithms that are used the same way as a traditional signature algorithm. The conservatively designed algorithms can be used in a mode of operation that mitigates the operational impact of a large signature size. The combination provides both the routine performance of the low-impact algorithm and a resilient fallback to the conservatively designed choice. The draft outlines the strategy, provides recommendations for future testing and deployment, and highlights operational considerations in adopting PQC for DNSSEC. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 19 April 2026. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. Sheth, et al. Expires 19 April 2026 [Page 1] Internet-Draft PQC Strategy for DNSSEC October 2025 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Conventions Used in This Document . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Post-Quantum DNSSEC Challenges . . . . . . . . . . . . . . . 3 3.1. Operational Constraints . . . . . . . . . . . . . . . . . 3 3.2. Deployment Cycles . . . . . . . . . . . . . . . . . . . . 3 4. Proposed PQC Algorithm Diversity Strategy . . . . . . . . . . 3 4.1. Mode of Operation . . . . . . . . . . . . . . . . . . . . 4 5. Alternatives and Considerations . . . . . . . . . . . . . . . 4 6. Recommended Next Steps . . . . . . . . . . . . . . . . . . . 4 7. Current Community Efforts . . . . . . . . . . . . . . . . . . 4 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 9. Security Considerations . . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 6 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8 Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Introduction DNSSEC [RFC4034][RFC4035][RFC9364] provides data origin authentication for DNS resource records. Current algorithms, such as RSASHA256 (8) and ECDSA (13), are vulnerable to cryptanalytically capable quantum computers. While "harvest now/decrypt later" is not a concern for DNSSEC, as it is for some other protocols such as TLS, "trust now/forge later" is a concern for DNSSEC. Ensuring that signatures are valid and secure from inception until expiration is critical. This combined with the fact that standards bodies like the Sheth, et al. Expires 19 April 2026 [Page 2] Internet-Draft PQC Strategy for DNSSEC October 2025 National Institute of Standards and Technology (NIST) are deprecating support for classical algorithms ensures that migration to post- quantum cryptography (PQC) is necessary. Unfortunately, migration with the large signature sizes introduce operational risks. This draft proposes a strategy deploying: * One or more conservatively designed PQC algorithm in a mode mitigating large signature sizes. * One or more low-impact drop-in PQC algorithm analogous to traditional DNSSEC signatures. This dual-algorithm approach ensures routine performance and resilient fallback during PQC transition. This draft is intended as a contribution to ongoing algorithm updates and the algorithm lifecycle per drafts [I-D.ietf-dnsop-rfc8624-bis] and[I-D.crocker-dnsop-dnssec-algorithm-lifecycle] 3. Post-Quantum DNSSEC Challenges 3.1. Operational Constraints DNS primarily runs over UDP, with packet sizes limited to a maximum of ~1232 bytes. Traditional signatures (e.g., RSASHA256, ECDSA) fit within this limit. PQC signatures (ML-DSA: 2420-4627 bytes, SLH-DSA: 7856-49856 bytes) exceed it, risking excessive TCP fallback, latency, and resolver performance degradation [Sury2025]. 3.2. Deployment Cycles DNSSEC upgrades occur over years. Novel PQC algorithms may face uncertain adoption timelines, requiring fallback mechanisms. Some algorithms (e.g., SQIsign) impose verification overhead, slowing response times [Sury2025]. 4. Proposed PQC Algorithm Diversity Strategy DNSSEC should deploy two types of PQC signature algorithms: Currently standardized post-quantum secure algorithms that provide cryptographic confidence and resilient fallback. Examples: SLH-DSA in Merkle Tree Ladder (MTL) mode [I-D.harvey-cfrg-mtl-mode], Falcon[FALCON], XMSS[RFC8391], LMS[RFC8554]. Sheth, et al. Expires 19 April 2026 [Page 3] Internet-Draft PQC Strategy for DNSSEC October 2025 New algorithms such as the ones that remain under NIST onramp evaluation or under consideration by other standards bodies. These provide routine performance with minimal operational impact. They may leverage newer but less well-established mathematical concepts. Examples: MAYO[MAYO], SNOVA[SNOVA]. 4.1. Mode of Operation MTL mode signs a Merkle tree ladder rather than individual DNS responses, amortizing signature size across multiple responses [Fregly2023]. In DNSSEC, this reduces operational impact while maintaining security[I-D.fregly-dnsop-slh-dsa-mtl-dnssec]. 5. Alternatives and Considerations * Conservative candidates: SLH-DSA, ML-DSA (possibly combined with traditional algorithms), Falcon, XMSS, LMS. * Low-impact candidates: New algorithms such as the ones that remain under NIST onramp evaluation or under consideration by other standards bodies. * Use of modes of operation (like MTL mode) to mitigate large signature sizes. 6. Recommended Next Steps * Conduct hackathons testing multiple algorithms in BIND, NSD, and CoreDNS (see current progress in Section 7). * Measure latency, fallback rates, and resilience under adversarial conditions, including KeyTrap-style attacks [HeBrig2024]. * Research countermeasures against denial-of-service risks for MTL mode. 7. Current Community Efforts Several efforts are underway to implement, test, and discuss PQC algorithms in DNSSEC. * IETF PQC DNSSEC Side Meeting - https://wiki.ietf.org/en/group/pq- dnssec * IETF 123 Hackathon - PQC DNSSEC Implementation [HACAKTHON-123] * IETF 122 Hackathon - PQC for DNSSEC - New Kids on the Block [HACAKTHON-122-NEW] * IETF 122 Hackathon - PQC DNSSEC Metrics with MTL Mode [HACAKTHON-122-MTL] Sheth, et al. Expires 19 April 2026 [Page 4] Internet-Draft PQC Strategy for DNSSEC October 2025 8. IANA Considerations This document makes no requests of IANA. Future work may include registration of new DNSSEC algorithm codes for PQC algorithms. 9. Security Considerations The deployment of PQC algorithms strengthens DNSSEC against quantum attacks but introduces operational risks. Proper testing, fallback mechanisms, and mode-of-operation considerations are essential to avoid new vulnerabilities. Continued community participation in PQC DNSSEC research, in particular around low-impact drop-in algorithms, is essential to standarizing secure PQC DNSSEC solutions. Additional considerations will be described based on continued analysis and feedback. 10. References 10.1. Normative References [I-D.crocker-dnsop-dnssec-algorithm-lifecycle] Crocker, S. and R. Housley, "Documenting and Managing DNSSEC Algorithm Lifecycles", Work in Progress, Internet- Draft, draft-crocker-dnsop-dnssec-algorithm-lifecycle-01, 4 October 2024, . [I-D.ietf-dnsop-rfc8624-bis] Hardaker, W. and W. Kumari, "DNSSEC Cryptographic Algorithm Recommendation Update Process", Work in Progress, Internet-Draft, draft-ietf-dnsop-rfc8624-bis-13, 4 June 2025, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Resource Records for the DNS Security Extensions", RFC 4034, DOI 10.17487/RFC4034, March 2005, . Sheth, et al. Expires 19 April 2026 [Page 5] Internet-Draft PQC Strategy for DNSSEC October 2025 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Protocol Modifications for the DNS Security Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237, RFC 9364, DOI 10.17487/RFC9364, February 2023, . 10.2. Informative References [FALCON] Fouque, P., Hoffstein, J., Kirchner, P., Lyubashevsky, V., Pornin, T., Prest, T., Ricosset, T., Seiler, G., Whyte, W., and Z. Zhang, "Falcon: Fast-Fourier Lattice-based Compact Signatures over NTRU", 10 January 2020, . [Fregly2023] Fregly, A., Harvey, J., Kaliski, B., and S. Sheth, "Merkle Tree Ladder Mode: Reducing the Size Impact of NIST PQC Signature Algorithms in Practice", 2022, . [HACAKTHON-122-MTL] Harvey, J. and S. Sheth, "IETF 122 - PQC DNSSEC Metrics with MTL Mode", 16 March 2025, . [HACAKTHON-122-NEW] Sury, O., "PQC for DNSSEC - New Kids on the Block", 16 March 2025, . [HACAKTHON-123] Jimenez-Berenguel, A., Harvey, J., Blanco-Romero, J., Sheth, S., Sury, O., and W. Toorop, "IETF 123 - PQC DNSSEC Implementation", July 2025, . Sheth, et al. Expires 19 April 2026 [Page 6] Internet-Draft PQC Strategy for DNSSEC October 2025 [HeBrig2024] Heftrig, E., Schulmann, H., Vogel, N., and M. Waidner, "The Harder You Try, The Harder You Fail: The KeyTrap Denial-of-Service Algorithmic Complexity Attacks on DNSSEC", 2024, . [I-D.fregly-dnsop-slh-dsa-mtl-dnssec] Fregly, A., Harvey, J., Kaliski, B., and D. Wessels, "Stateless Hash-Based Signatures in Merkle Tree Ladder Mode (SLH-DSA-MTL) for DNSSEC", Work in Progress, Internet-Draft, draft-fregly-dnsop-slh-dsa-mtl-dnssec-05, 30 September 2025, . [I-D.harvey-cfrg-mtl-mode] Harvey, J., Kaliski, B., Fregly, A., and S. Sheth, "Merkle Tree Ladder (MTL) Mode Signatures", Work in Progress, Internet-Draft, draft-harvey-cfrg-mtl-mode-07, 9 September 2025, . [MAYO] Beullens, W., Campos, F., Celi, S., Hess, B., and M. Kannwischer, "MAYO", 5 February 2025, . [RFC8391] Huelsing, A., Butin, D., Gazdag, S., Rijneveld, J., and A. Mohaisen, "XMSS: eXtended Merkle Signature Scheme", RFC 8391, DOI 10.17487/RFC8391, May 2018, . [RFC8554] McGrew, D., Curcio, M., and S. Fluhrer, "Leighton-Micali Hash-Based Signatures", RFC 8554, DOI 10.17487/RFC8554, April 2019, . [SNOVA] Wang, L., Chou, C., Ding, J., Kuan, Y., Leegwater, J., Li, M., Tseng, B., Tseng, P., and C. Wang, "SNOVA Proposal for NISTPQC: Additional Digital Signature Schemes", 25 January 2025, . [Sury2025] Sury, O., "Feasibility of the new Post Quantum Cryptography for DNSSEC", 2025, . Sheth, et al. Expires 19 April 2026 [Page 7] Internet-Draft PQC Strategy for DNSSEC October 2025 Acknowledgements Thanks to Andrew Fregly for early contributions in promoting PQ DNSSEC and uniting the research community around a post-quantum research agenda. Change Log 00: Initial draft of the document. Authors' Addresses Swapneel Sheth Verisign Labs 12061 Bluemont Way Reston, VA 20190 United States of America Email: ssheth@verisign.com URI: https://www.verisignlabs.com/ Taejoong Chung Virginia Tech 220 Gilbert Street, RM 4303 Blacksburg, VA 24060 United States of America Email: tijay@vt.edu URI: https://www.vt.edu/ Benno Overeinder NLnet Labs Science Park 400 1098 XH Amsterdam Netherlands Email: benno@nlnetlabs.nl URI: https://nlnetlabs.nl Sheth, et al. Expires 19 April 2026 [Page 8]