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Today, the latest issue of The Domain Name Industry Brief Quarterly Report was released by DNIB.com, showing the first quarter of 2024 closed with 362.4 million domain name registrations across all top-level domains (TLDs), an increase of 2.5 million domain name registrations, or 0.7%, compared to the fourth quarter of 2023. Domain name registrations also increased by 7.5 million, or 2.1%, year over year.
Starting with the Q1 2024 report, the DNIB Quarterly Report now includes new information on quarterly renewal percentages for all TLDs, as available, summary information on other legacy gTLDs as a group and an expanded overall analysis of gTLDs.
Check out the latest issue of The Domain Name Industry Brief Quarterly Report to see domain name stats from the first quarter of 2024, including:
Top 10 largest TLDs by number of reported domain names, with quarterly renewal percentages when available
Top 10 largest ccTLDs by number of reported domain names, with quarterly renewal percentages when available
Top 10 largest gTLDs by number of reported domain names, with quarterly renewal percentages and other key statistics
Every day, there are tens of thousands of domain names registered across the globe – often as a key first step in creating a unique online presence. Making that experience possible for Verisign-operated top-level domains (TLDs) like .com and .net is a powerful and flexible technology platform first introduced 25 years ago.
Thanks to the Shared Registration System (SRS) – a hardware and software system conceptualized, designed, and launched by our teams 25 years ago – we’re able to successfully manage relationships with approximately 2,000 ICANN-accredited registrars who generally submit more than 100 million domain name transactions daily. Over the past quarter century, the SRS has thrived and grown with the global internet, in large part because we’ve continuously scaled and evolved the technology to meet exponentially increasing global demand, and a rapidly changing cyberthreat landscape.
In addition to enabling domain name registration, the usefulness of the technology extends beyond Verisign and its registry operations: many other companies subsequently adopted SRS concepts and implemented their own shared registration systems, making its impact far-reaching and long-lasting.
In this blog post, we commemorate the 25th anniversary of the launch of the Verisign SRS by reflecting on the insight and collaboration that went into developing a structure for domain name registration in those early days of the internet’s mainstream adoption.
When It All Began
Network Solutions, which Verisign acquired in 2000, had been functioning as both the sole registry and registrar for TLDs including .com, .net, and .org prior to 1999. The SRS was initially developed to make domain name registration more competitive and to encourage greater international participation, consistent with The Framework for Global Electronic Commerce, a directive to the U.S. Department of Commerce (DoC) to privatize the internet’s Domain Name System (DNS).
Work began in 1998 to develop and implement the SRS so that an unlimited number of registrars could provide domain name registration services, all under the administration of a common registry for each TLD. For several high-profile TLDs – including .com and .net – that registry was Network Solutions. That same year, the Internet Corporation for Assigned Names and Numbers (ICANN) – a multistakeholder not-for-profit organization dedicated to the management of key elements of the DNS – was formed.
Designing and Deploying the System
Over a period of several months, Network Solutions designed and installed the system, which was officially deployed on April 3, 1999. Through a testing period that ran through the second half of 1999, the number of test registrars grew from an initial five – AOL, CORE, France Telecom/Oleane, Melbourne IT, and Register.com – to more than 20 by the end of that year.
That same year, Network Solutions implemented modifications to the SRS so that a registrar could accept registrations and renewals in one-year increments, as well as enable a registrar to add one year to a registrant’s registration period when transferring a domain from one registrar to another. Once the SRS was live, it was made accessible to all ICANN-accredited registrars, providing each one with equivalent access to register domain names in the TLDs.
Moving Forward: The Extensible Provisioning Protocol
When the SRS was first launched, a simple protocol called the Registry-Registrar Protocol (RRP) was deployed to handle the registration and management of domain names by many registrars in one TLD. However, we recognized that the use of this protocol could only be temporary given the growth of the internet and the need for a registration system with increased scalability. Work on a more sophisticated registration system began almost immediately – in 1999 – and that came in the form of the Extensible Provisioning Protocol, or EPP. EPP officially became an Internet Standard in 2009.
Today, EPP is used to register domain names and perform domain name-related functions, and there are over 2,000 ICANN-accredited registrars that all use EPP. EPP is central to the way that Verisign and many other authoritative registry operators do business: these registry operators work with domain name registrars to register domain names, and the registrars in turn offer a diverse range of domain name products to end users. Indeed, the simplicity of registering domains through EPP, and, for TLDs operated by Verisign, through the SRS, not only opened the door to easy access to domain name registration services, but also paved the way for new digital commerce and communications capabilities.
Powering Registrations in the Past, Present, and Future
For the past 25 years, the SRS has been a critical component of the internet’s backend technology, even though it’s not widely known outside the DNS community. Thanks to the foresight and planning of many talented technologists, we built and evolved this system in such a way that it has successfully supported hundreds of millions of domain name registrations across the globe, serving as a first step for many on the path to establishing durable online identities. Along the way, we’ve added support for new technologies, including DNSSEC and Internationalized Domain Names (IDNs). We’ve made the system more secure by strengthening the domain name locking and transfer processes. We’ve also expanded the SRS to support additional TLDs administered by Verisign. In its own quiet way, the SRS has helped to support the dynamic growth of the internet, while prioritizing equivalent access to domain name registration.
Many of the people who worked on the launch of the SRS are still with Verisign today, myself included. We are fortunate to have the chance to continue working together – 25 years later – always with an eye toward the future and how we can continue to help the internet grow and prosper.
Today, the latest issue of The Domain Name Industry Brief Quarterly Report was released by DNIB.com, showing the fourth quarter of 2023 closed with 359.8 million domain name registrations across all top-level domains (TLDs), an increase of 0.6 million domain name registrations, or 0.2%, compared to the third quarter of 2023. Domain name registrations also increased by 8.9 million, or 2.5%, year over year.
Check out the latest issue of The Domain Name Industry Brief Quarterly Report to see domain name stats from the fourth quarter of 2023, including:
Top 10 largest TLDs by number of reported domain names
Top 10 largest ccTLDs by number of reported domain names
ngTLDs as percentage of total TLDs
Geographical ngTLDs as percentage of total corresponding geographical TLDs
The quantum computing era is coming, and it will change everything about how the world connects online. While quantum computing will yield tremendous benefits, it will also create new risks, so it’s essential that we prepare our critical internet infrastructure for what’s to come. That’s why we’re so pleased to share our latest efforts in this area, including technology that we’re making available as an open source implementation to help internet operators worldwide prepare.
In recent years, the research team here at Verisign has been focused on a future where quantum computing is a reality, and where the general best practices and guidelines of traditional cryptography are re-imagined. As part of that work, we’ve made three further contributions to help the DNS community prepare for these changes:
a new I-D on using MTL mode signatures with DNS Security Extensions (DNSSEC); and
an expansion of our previously announced public license terms to include royalty-free terms for implementing and using MTL mode if the I-Ds are published as Experimental, Informational, or Standards Track Requests for Comments (RFCs). (See the MTL mode I-D IPR declaration and the MTL mode for DNSSEC I-D IPR declaration for the official language.)
About MTL Mode
First, a brief refresher on what MTL mode is and what it accomplishes:
MTL mode is a technique developed by Verisign researchers that can reduce the operational impact of a signature scheme when authenticating an evolving series of messages. Rather than signing messages individually, MTL mode signs structures called Merkle tree ladders that are derived from the messages to be authenticated. Individual messages are authenticated relative to a ladder using a Merkle tree authentication path, while ladders are authenticated relative to a public key of an underlying signature scheme using a digital signature. The size and computational cost of the underlying digital signatures can therefore be spread across multiple messages.
The reduction in operational impact achieved by MTL mode can be particularly beneficial when the mode is applied to a signature scheme that has a large signature size or computational cost in specific use cases, such as when post-quantum signature schemes are applied to DNSSEC.
Recently, Verisign Fellow Duane Wessels described how Verisign’s DNSSEC algorithm update — from RSA/SHA-256 (Algorithm 8) to ECDSA Curve P-256 with SHA-256 (Algorithm 13) — increases the security strength of DNSSEC signatures and reduces their size impact. The present update is a logical next step in the evolution of DNSSEC resiliency. In the future, it is possible that DNSSEC may utilize a post-quantum signature scheme. Among the new post-quantum signature schemes currently being standardized, though, there is a shortcoming; if we were to directly apply these schemes to DNSSEC, it would significantly increase the size of the signatures1. With our work on MTL mode, the researchers at Verisign have provided a way to achieve the security benefit of a post-quantum algorithm rollover in a way that mitigates the size impact.
Put simply, this means that in a quantum environment, the MTL mode of operation developed by Verisign will enable internet infrastructure operators to use the longer signatures they will need to protect communications from quantum attacks, while still supporting the speed and space efficiency we’ve come to expect.
In my July 2023 blog post titled “Next Steps in Preparing for Post-Quantum DNSSEC,” I described two recent contributions by Verisign to help the DNS community prepare for a post-quantum world: the MTL mode I-D and a public, royalty-free license to certain intellectual property related to that I-D. These activities set the stage for the latest contributions I’m announcing in this post today.
Our Latest Contributions
Open source implementation. Like the I-D we published in July of this year, the open source implementation focuses on applying MTL mode to the SPHINCS+ signature scheme currently being standardized in FIPS 205 as SLH-DSA (Stateless Hash-Based Digital Signature Algorithm) by the National Institute of Standards and Technology (NIST). We chose SPHINCS+ because it is the most conservative of NIST’s post-quantum signature algorithms from a cryptographic perspective, being hash-based and stateless. We remain open to adding other post-quantum signature schemes to the I-D and to the open source implementation.
We encourage developers to try out the open source implementation of MTL mode, which we introduced at the IETF 118 Hackathon, as the community’s experience will help improve the understanding of MTL mode and its applications, and thereby facilitate its standardization. We are interested in feedback both on whether MTL mode is effective in reducing the size impact of post-quantum signatures on DNSSEC and other use cases, and on the open source implementation itself. We are particularly interested in the community’s input on what language bindings would be useful and on which cryptographic libraries we should support initially. The open source implementation can be found on GitHub at: https://github.com/verisign/MTL
MTL mode for DNSSEC I-D. This specification describes how to use MTL mode signatures with DNSSEC, including DNSKEY and RRSIG record formats. The I-D also provides initial guidance for DNSSEC key creation, signature generation, and signature verification in MTL mode. We consider the I-D as an example of the kinds of contributions that can help to address the “Research Agenda for a Post-Quantum DNSSEC,” the subject of another I-D recently co-authored by Verisign. We expect to continue to update this I-D based on community feedback. While our primary focus is on the DNSSEC use case, we are also open to collaborating on other applications of MTL mode.
Expanded patent license. Verisign previously announced a public, royalty-free license to certain intellectual property related to the MTL mode I-D that we published in July 2023. With the availability of the open source implementation and the MTL mode for DNSSEC specification, the company has expanded its public license terms to include royalty-free terms for implementing and using MTL mode if the I-D is published as an Experimental, Informational, or Standards Track RFC. In addition, the company has made a similar license grant for the use of MTL mode with DNSSEC. See the MTL mode I-D IPR declaration and the MTL mode for DNSSEC I-D IPR declaration for the official language.
Verisign is grateful for the DNS community’s interest in this area, and we are pleased to serve as stewards of the internet when it comes to developing new technology that can help the internet grow and thrive. Our work on MTL mode is one of the longer-term efforts supporting our mission to enhance the security, stability, and resiliency of the global DNS. We’re encouraged by the progress that has been achieved, and we look forward to further collaborations as we prepare for a post-quantum future.
Footnotes
While it’s possible that other post-quantum algorithms could be standardized that don’t have large signatures, they wouldn’t have been studied for as long. Indeed, our preferred approach for long-term resilience of DNSSEC is to use the most conservative of the post-quantum signature algorithms, which also happens to have the largest signatures. By making that choice practical, we’ll have a solution in place whether or not a post-quantum algorithm with a smaller signature size is eventually available. ︎
Today, the latest issue of The Domain Name Industry Brief Quarterly Report was released by DNIB.com, showing the third quarter of 2023 closed with 359.3 million domain name registrations across all top-level domains (TLDs), an increase of 2.7 million domain name registrations, or 0.8%, compared to the second quarter of 2023. Domain name registrations also increased by 8.5 million, or 2.4%, year over year.
Check out the latest issue of The Domain Name Industry Brief Quarterly Report to see domain name stats from the third quarter of 2023, including:
Top 10 largest TLDs by number of reported domain names
Top 10 largest ccTLDs by number of reported domain names
ngTLDs as percentage of total TLDs
Geographical ngTLDs as percentage of total corresponding geographical TLDs
Celebrating National Hispanic Heritage Month reminds us how the wide range of perspectives and experiences among our employees makes us stronger both as a company and as a steward of the internet. In honor of this month, we are proud to recognize the stories of three of our Hispanic employees, and the positive impact they make at Verisign.
Carlos Ruesta
As Verisign’s director of information security, Carlos Ruesta draws inspiration from his father’s community commitment as an agricultural engineer in Peru, working to bring safe food and water to isolated communities. His father’s experiences inform Carlos’ belief in Verisign’s mission of enabling the world to connect online with reliability and confidence, anytime, anywhere and motivates his work as part of a team that ensures trust.
As a leader in our security compliance division, Carlos ensures that his team maintains a robust governance, risk, and compliance framework, translating applicable laws and regulations into security control requirements. “Being part of a team that emphasizes trust, motivates me,” he said. “Management trusts me to make decisions affecting large-scale projects that protect our company. This allows me to use my problem-solving skills and leadership abilities.”
Carlos commends Verisign’s respectful and encouraging environment, which he considers vital in cultivating successful career paths for newcomers navigating the cybersecurity field. He says by recognizing individual contributions and supporting each other’s professional growth, Hispanic employees at Verisign feel a sense of belonging in the workplace and are able to excel in their career journeys.
Alejandro Gonzalez Roman
Alejandro Gonzalez Roman, a senior UX designer at Verisign, combines his artistic talent with technical expertise in his role, collaborating among various departments across Verisign. “My dad is an artist, and still one of my biggest role models,” he said. “He taught me that to be good at anything means to dedicate a lot of time to perfecting your craft. I see art as a way to inspire people to make the world a better place. In my job as a UX designer, I use art to make life a little easier for people.”
As a UX designer, Alejandro strives to make technology accessible to everyone, regardless of background or abilities. He believes that life experiences and cultural knowledge provide individuals with a unique perspective, which he considers an invaluable source of inspiration when designing. And with the Hispanic population being one of the largest minorities in the United States, cultural knowledge is crucial. Understanding how different people interact with technology and integrating cultural insights into the work is essential to good UX design.
Overall, Alejandro is motivated by the strong sense of teamwork at Verisign. “Day-to-day work with our strong team has helped me improve my work” he said. “With collaboration and encouragement, we push each other to be better UX designers. I couldn’t succeed as I have without this amazing team around me.”
Rebecca Bustamante
Rebecca Bustamante, senior manager of operations analysis, says Verisign’s “people-first” culture is part of her motivation, and she is grateful for the opportunities that allowed her to take on different roles within the company to learn and broaden her skills. “I’ve had opportunities because people believed in my potential and saw my work ethic,” she said. “These experiences have given me the understanding and skills to succeed at the job I have today.”
One of these experiences was joining the WIT@Verisign (Women in Technology) leadership team, which proved instrumental to her personal growth and led to valuable work friendships. In fact, one of her most cherished memories at Verisign includes leading a Verisign Cares team project in Virginia’s Great Falls Park, where she and her coworkers worked together to clear invasive plants and renovate walking paths.
Rebecca sees this type of camaraderie among employees as a crucial part of the people-first culture at Verisign. She particularly commends Verisign’s team leaders who value consistent communication and take the time to listen to people’s stories, which fosters an authentic understanding. This approach makes collaboration more natural and allows teamwork to develop organically. Rebecca emphasizes the significance of celebrating her culture, as it directly influences her job performance and effective communication. But she pointed out that the term “Hispanic” encompasses a wide diversity of peoples and nations. She advocates respect, practices active listening, and promotes a culture celebrating each other’s successes.
Joining the Verisign Team
These three individuals – as well as their many team members – contribute to Verisign’s efforts to enable and enhance the security, stability, and resiliency of key internet infrastructure every single day.
At Verisign, we recognize the importance of talent and culture in driving an environment that fosters high performance, inclusion, and integrity in all aspects of our work. It’s why recruiting and retaining the very best talent is our continual focus. If you would like to be part of the Verisign Team, please visit Verisign Careers.
Today, the latest issue of The Domain Name Industry Brief Quarterly Report was released by DNIB.com, showing the second quarter of 2023 closed with 356.6 million domain name registrations across all top-level domains (TLDs), an increase of 1.7 million domain name registrations, or 0.5%, compared to the first quarter of 2023. Domain name registrations also increased by 4.3 million, or 1.2%, year over year.
Top 10 largest TLDs by number of reported domain names
Top 10 largest ccTLDs by number of reported domain names
ngTLDs as percentage of total TLDs
Geographical ngTLDs as percentage of total corresponding geographical TLDs
With the launch of the DNIB.com dashboards, 16 additional TLDs have been included in applicable calculations. The applicable current and historical data presented in this edition of the quarterly report have been adjusted accordingly, and applicable quarterly and year-over-year trends have been calculated using those adjusted figures. More information is available at DNIB.com.
As part of Verisign’s ongoing effort to make global internet infrastructure more secure, stable, and resilient, we will soon make an important technology update to how we protect the top-level domains (TLDs) we operate. The vast majority of internet users won’t notice any difference, but the update will support enhanced security for several Verisign-operated TLDs and pave the way for broader adoption and the next era of Domain Name System (DNS) security measures.
Beginning in the next few months and continuing through the end of 2023, we will upgrade the algorithm we use to sign domain names in the .com, .net, and .edu zones with Domain Name System Security Extensions (DNSSEC).
In this blog, we’ll outline the details of the upcoming change and what members of the DNS technical community need to know.
DNSSEC Adoption
DNSSEC provides data authentication security to DNS responses. It does this by ensuring any altered data can be detected and blocked, thereby preserving the integrity of DNS data. Think of it as a chain of trust – one that helps avoid misdirection and allows users to trust that they have gotten to their intended online destination safely and securely.
Verisign has long been at the forefront of DNSSEC adoption. In 2010, a major milestone occurred when the Internet Corporation for Assigned Names and Numbers (ICANN) and Verisign signed the DNS root zone with DNSSEC. Shortly after, Verisign introduced DNSSEC to its TLDs, beginning with .edu in mid-2010, .net in late 2010, and .com in early 2011. Additional TLDs operated by Verisign were subsequently signed as well.
In the time since we signed our TLDs, we have worked continuously to help members of the internet ecosystem take advantage of DNSSEC. We do this through a wide range of activities, including publishing technical resources, leading educational sessions, and advocating for DNSSEC adoption in industry and technical forums.
Growth Over Time
Since the TLDs were first signed, we have observed two very distinct phases of growth in the number of signed second-level domains (SLDs).
The first growth phase occurred from 2012 to 2020. During that time, signed domains in the .com zone grew at about 0.1% of the base per year on average, reaching just over 1% by the end of 2020. In the .net zone, signed domains grew at about 0.1% of the base per year on average, reaching 1.2% by the end of 2020. These numbers demonstrated a slow but steady increase, which can be seen in Figure 1.
Figure 1: A chart spanning 2010 through the present shows the number of .com and .net domain names with DS – or Delegation Signer – records. These records form a link in the DNSSEC chain-of-trust for signed domains, indicating an uptick in DNSSEC adoption among SLDs.
We’ve observed more pronounced growth in signed SLDs during the second growth phase, which began in 2020. This is largely due to a single registrar that enabled DNSSEC by default for their new registrations. For .com, the annual rate increased to 0.9% of the base, and for .net, it increased to 1.1% of the base. Currently, 4.2% of .com domains are signed and 5.1% of .net domains are signed. This accelerated growth is also visible in Figure 1.
As we look forward, Verisign anticipates continued growth in the number of domains signed with DNSSEC. To support continued adoption and help further secure the DNS, we’re planning to make one very important change.
Rolling the Algorithm
All Verisign TLDs are currently signed with DNSSEC algorithm 8, also known as RSA/SHA-256, as documented in our DNSSEC Practice Statements. Currently, we use a 2048-bit Key Signing Key (KSK), and 1280-bit Zone Signing Keys (ZSK). The RSA algorithm has served us (and the broader internet) well for many years, but we wanted to take the opportunity to implement more robust security measures while also making more efficient use of resources that support DNSSEC-signed domain names.
Support for DNSSEC signing and validation with ECDSA has been well-established by various managed DNS providers, 78 other TLDs, and nearly 10 million signed SLDs. Additionally, research performed by APNIC and NLnet Labs shows that ECDSA support in validating resolvers has increased significantly in recent years.
The Road to Algorithm 13
How did we get to this point? It took a lot of careful preparation and planning, but with internet stewardship at the forefront of our mission, we wanted to protect the DNS with the best technologies available to us. This means taking precise measures in everything we do, and this transition is no exception.
Initial Planning
Algorithm 13 was on our radar for several years before we officially kicked off the implementation process this year. As mentioned previously, the primary motivating properties were the smaller signature size, with each signature being 96 bytes smaller than our current RSA signatures (160 bytes vs. 64 bytes), and the improved cryptographic strength. This helps us plan for the future and prepare for a world where more domain names are signed with DNSSEC.
Testing
Each TLD will first implement the rollover to algorithm 13 in Verisign’s Operational Test & Evaluation (OT&E) environment prior to implementing the process in production, for a total of two rollovers per TLD. Combined, this will result in six total rollovers across the .com, .net, and .edu TLDs. Rollovers between the individual TLDs will be spaced out to avoid overlap where possible.
The algorithm rollover for each TLD will follow this sequence of events:
Publish algorithm 13 DNSKEY records alongside algorithm 8 DNSKEY records
Publish the algorithm 13 DS record in the root zone and stop publishing the algorithm 8 DS record
Stop publishing algorithm 8 DNSKEY records
Stop publishing algorithm 8 ZSK signatures
Only when a successful rollover has been done in OT&E will we begin the process in production.
Who is affected, and when is the change happening?
Now that we’ve given the background, we know you’re wondering: how might this affect me?
The change to a new DNSSEC-signing algorithm is expected to have no impact for the vast majority of internet users, service providers, and domain registrants. According to the aforementioned research by APNIC and NLnet Labs, most DNSSEC validators support ECDSA, and any that do not will simply ignore the signatures and still be able to resolve domains in Verisign-operated TLDs.
Regarding timing, we plan to begin to transition to ECDSA in the third and fourth quarters of this year. We will start the transition process with .edu, then .net, and then .com. We are currently aiming to have these three TLDs transitioned before the end of the fourth quarter 2023, but we will let the community know if our timeline shifts.
Conclusion
As leaders in DNSSEC adoption, this algorithm rollover demonstrates yet another critical step we are taking toward making the internet more secure, stable, and resilient. We look forward to enabling the change later this year, providing more efficient and stronger cryptographic security while optimizing resource utilization for DNSSEC-signed domain names.
In 2021, we discussed a potential future shift from established public-key algorithms to so-called “post-quantum” algorithms, which may help protect sensitive information after the advent of quantum computers. We also shared some of our initial research on how to apply these algorithms to the Domain Name System Security Extensions, or DNSSEC. In the time since that blog post, we’ve continued to explore ways to address the potential operational impact of post-quantum algorithms on DNSSEC, while also closely tracking industry research and advances in this area.
Now, significant activities are underway that are setting the timeline for the availability and adoption of post-quantum algorithms. Since DNS participants – including registries and registrars – use public key-cryptography in a number of their systems, these systems may all eventually need to be updated to use the new post-quantum algorithms. We also announce two major contributions that Verisign has made in support of standardizing this technology: an Internet-Draft as well as a public, royalty-free license to certain intellectual property related to that Internet-Draft.
In this blog post, we review the changes that are on the horizon and what they mean for the DNS ecosystem, and one way we are proposing to ease the implementation of post-quantum signatures – Merkle Tree Ladder mode.
By taking these actions, we aim to be better prepared (while also helping others prepare) for a future where cryptanalytically relevant quantum computing and post-quantum cryptography become a reality.
Recent Developments
In July 2022, the National Institute of Standards and Technology (NIST) selected one post-quantum encryption algorithm and three post-quantum signature algorithms for standardization, with standards for these algorithms arriving as early as 2024. In line with this work, the Internet Engineering Task Force (IETF) has also started standards development activities on applying post-quantum algorithms to internet protocols in various working groups, including the newly formed Post-Quantum Use in Protocols (PQUIP) working group. And finally, the National Security Agency (NSA) recently announced that National Security Systems are expected to transition to post-quantum algorithms by 2035.
Collectively, these announcements and activities indicate that many organizations are envisioning a (post-)quantum future, across many protocols. Verisign’s main concern continues to be how post-quantum cryptography impacts the DNS, and in particular, how post-quantum signature algorithms impact DNSSEC.
DNSSEC Considerations
The standards being developed in the next few years are likely to be the ones deployed when the post-quantum transition eventually takes place, so now is the time to take operational requirements for specific protocols into account.
For DNSSEC, the operational concerns are twofold.
First, the large signature sizes of current post-quantum signatures selected by NIST would result in DNSSEC responses that exceed the size limits of the User Datagram Protocol, which is broadly deployed in the DNS ecosystem. While the Transmission Control Protocol and other transports are available, the additional overhead of having large post-quantum signatures on every response — which can be one to two orders of magnitude as long as traditional signatures —introduces operational risk to the DNS ecosystem that would be preferable to avoid.
Second, the large signatures would significantly increase memory requirements for resolvers using in-memory caches and authoritative nameservers using in-memory databases.
Figure 1: Size impact of traditional and post-quantum signature size impact on a fully signed DNS zone. Horizontal bars show percentage of zone that would be signature for two traditional and two post-quantum algorithms; vertical bars show the percentage increase in the zone size due to signature data.
Figure 1, from Andy Fregly’s recent presentation at OARC 40, shows the impact on a fully signed DNS zone where, on average, there are 2.2 digital signatures per resource record set (covering both existence and non-existence proofs). The horizontal bars show the percentage of the zone file that would be comprised of signature data for the two prevalent current algorithms, RSA and ECDSA, and for the smallest and largest of the NIST PQC algorithms. At the low and high end of these examples, signatures with ECDSA would take up 40% of the zone and SPHINCS+ signatures would take up over 99% of the zone. The vertical bars give the percentage size increase of the zone file due to signatures. Again, comparing the low and high end, a zone fully signed with SPHINCS+ would be about 50 times the size of a zone fully signed with ECDSA.
Merkle Tree Ladder Mode: Reducing Size Impact of Post-Quantum Signatures
In his 1988 article, “The First Ten Years of Public-Key Cryptography,” Whitfield Diffie, co-discoverer of public-key cryptography, commented on the lack of progress in finding public-key encryption algorithms that were as fast as the symmetric-key algorithms of the day: “Theorems or not, it seemed silly to expect that adding a major new criterion to the requirements of a cryptographic system could fail to slow it down.”
Diffie’s counsel also appears relevant to the search for post-quantum algorithms: It would similarly be surprising if adding the “major new criterion” of post-quantum security to the requirements of a digital signature algorithm didn’t impact performance in some way. Signature size may well be the tradeoff for post-quantum security, at least for now.
With this tradeoff in mind, Verisign’s post-quantum research team has explored ways to address the size impact, particularly to DNSSEC, arriving at a construction we call a Merkle Tree Ladder (MTL), a generalization of a single-rooted Merkle tree (see Figure 2). We have also defined a technique that we call the Merkle Tree Ladder mode of operation for using the construction with an underlying signature algorithm.
Figure 2: A Merkle Tree Ladder consists of one or more “rungs” that authenticate or “cover” the leaves of a generalized Merkle tree. In this example, rungs 19:19, 17:18, and 1:16 are the collectively the ancestors of all 19 leaves of the tree and therefore cover them. The values of the nodes are the hash of the values of their children, providing cryptographic protection. A Merkle authentication path consisting of sibling nodes authenticates a leaf node relative to the ladder e.g., leaf node 7 (corresponding to message 7 beneath) can be authenticated relative to rung 1:16 by rehashing it with the sibling nodes along the path 8, 5:6, 1:4 and 9:16. If the verifier already has a previous ladder that covers a message, the verifier can instead rehash relative to that ladder, e.g., leaf node 7 can be verified relative to rung 1:8 using sibling nodes 8, 5:6 and 1:4.
Similar to current deployments of public-key cryptography, MTL mode combines processes with complementary properties to balance performance and other criteria (see Table 1). In particular, in MTL mode, rather than signing individual messages with a post-quantum signature algorithm, ladders comprised of one or more Merkle tree nodes are signed using the post-quantum algorithm. Individual messages are then authenticated relative to the ladders using Merkle authentication paths.
Criterion to Achieve
Initial Design with a Single Process
Improved Design Combining Complementary Processes
Benefit
Public-Key Property for Encryption
– Encrypt Individual Messages with Public-Key Algorithm
– Establish Symmetric Keys Using Public-Key Algorithm
– Encrypt Multiple Messages Using Each Symmetric Key
– Amortize Cost of Public-Key Operations Across Multiple Messages
Post-Quantum Property for Signatures
– Sign Individual Messages with Post-Quantum Algorithm
– Sign Merkle Tree Ladders using Post-Quantum Algorithm
– Authenticate Multiple Messages Relative to Each Signed Ladder
– Amortize Size of Post-Quantum Signature Across Multiple Messages
Table 1: Speed concerns for traditional public-key algorithms were addressed by combining them with symmetric-key algorithms (for instance, as outlined in early specifications for Internet Privacy-Enhanced Mail). Size concerns for emerging post-quantum signature algorithms can potentially be addressed by combining them with constructions such as Merkle Tree Ladders.
Although the signatures on the ladders might be relatively large, the ladders and their signatures are sent infrequently. In contrast, the Merkle authentication paths that are sent for each message are relatively short. The combination of the two processes maintains the post-quantum property while amortizing the size impact of the signatures across multiple messages. (Merkle tree constructions, being based on hash functions, are naturally post-quantum.)
The two-part approach for public-key algorithms has worked well in practice. In Transport Layer Security, symmetric keys are established in occasional handshake operations, which may be more expensive. The symmetric keys are then used to encrypt multiple messages within a session without further overhead for key establishment. (They can also be used to start a new session).
We expect that a two-part approach for post-quantum signatures can similarly work well in an application like DNSSEC where verifiers are interested in authenticating a subset of messages from a large, evolving message series (e.g., DNS records).
In such applications, signed Merkle Tree Ladders covering a range of messages in the evolving series can be provided to a verifier occasionally. Verifiers can then authenticate messages relative to the ladders, given just a short Merkle authentication path.
Importantly, due to a property of Merkle authentication paths called backward compatibility, all verifiers can be given the same authentication path relative to the signer’s current ladder. This also helps with deployment in applications such as DNSSEC, since the authentication path can be published in place of a traditional signature. An individual verifier may verify the authentication path as long as the verifier has a previously signed ladder covering the message of interest. If not, then the verifier just needs to get the current ladder.
As reported in our presentation on MTL mode at the RSA Conference Cryptographers’ Track in April 2023, our initial evaluation of the expected frequency of requests for MTL mode signed ladders in DNSSEC is promising, suggesting that a significant reduction in effective signature size impact can be achieved.
Verisign’s Contributions to Standardization
To facilitate more public evaluation of MTL mode, Verisign’s post-quantum research team last week published the Internet-Draft “Merkle Tree Ladder Mode (MTL) Signatures.” The draft provides the first detailed, interoperable specification for applying MTL mode to a signature scheme, with SPHINCS+ as an initial example.
We chose SPHINCS+ because it is the most conservative of the NIST PQC algorithms from a cryptographic perspective, being hash-based and stateless. It is arguably most suited to be one of the algorithms in a long-term deployment of a critical infrastructure service like DNSSEC. With this focus, the specification has a “SPHINCS+-friendly” style. Implementers familiar with SPHINCS+ will find similar notation and constructions as well as common hash function instantiations. We are open to adding other post-quantum signature schemes to the draft or other drafts in the future.
Publishing the Internet-Draft is a first step toward the goal of standardizing a mode of operation that can reduce the size impact of post-quantum signature algorithms.
In support of this goal, Verisign also announced this week a public, royalty-free license to certain intellectual property related to the Internet-Draft published last week. Similar to other intellectual property rights declarations the company has made, we have announced a “Standards Development Grant” which provides the listed intellectual property under royalty-free terms for the purpose of facilitating standardization of the Internet-Draft we published on July 10, 2023. (The IPR declaration gives the official language.)
We expect to release an open-source implementation of the Internet-Draft soon, and, later this year, to publish an Internet-Draft on using MTL mode signatures in DNSSEC.
With these contributions, we invite implementers to take part in the next step toward standardization: evaluating initial versions of MTL mode to confirm whether they indeed provide practical advantages in specific use cases.
Conclusion
DNSSEC continues to be an important part of the internet’s infrastructure, providing cryptographic verification of information associated with the unique, stable identifiers in this ubiquitous namespace. That is why preparing for an eventual transition to post-quantum algorithms for DNSSEC has been and continues to be a key research and development activity at Verisign, as evidenced by our work on MTL mode and post-quantum DNSSEC more generally.
Our goal is that with a technique like MTL mode in place, protocols like DNSSEC can preserve the security characteristics of a pre-quantum environment while minimizing the operational impact of larger signatures in a post-quantum world.
In a later blog post, we’ll share more details on some upcoming changes to DNSSEC, and how these changes will provide both security and operational benefits to DNSSEC in the near term.
Verisign plans to continue to invest in research and standards development in this area, as we help prepare for a post-quantum future.
Verisign today announced the launch of DNIB.com, the new Domain Name Industry Brief (DNIB) website.
Sponsored by Verisign, DNIB.com is a source for insights and analysis from subject-matter experts on key topics relevant to the global Domain Name System (DNS). DNIB.com will offer insight on policy, governance, technology, security, and business trends relevant to analysts, entrepreneurs, policymakers, and anyone with an interest in the DNS. The website features a collection of new, searchable, and interactive dashboards tracking relevant DNS data and trends, that is designed to be a valuable day-to-day resource for industry stakeholders, and anyone interested in learning more about global domain name operations.
DNIB.com is also the new home of the DNIB quarterly report, which Verisign has published for more than a decade, providing a trusted and valued resource for stakeholders across the globe seeking to understand the dynamism and trends of the domain name industry.
The report will be published each quarter at DNIB.com, summarizing the state of the domain name industry through a variety of statistical and analytical research. The new and expanded DNIB.com dashboards take that statistical data to the next level, enabling exploration of trend data across the industry, providing additional history and depth, and offering expert insights and commentary.
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Announcing the Launch of DNIB.com, a New Source for DNS News, Information, Research, and Analysis
2023-06-22 20:30 UTC by Verisign
