A few weeks ago, on Oct. 1, 2016, Verisign successfully doubled the size of the cryptographic key that generates Domain Name System Security Extensions (DNSSEC) signatures for the internet’s DNS root zone. With this change, root zone Domain Name System (DNS) responses can be fully validated using 2048-bit RSA keys. This project involved work by numerous people within Verisign, as well as collaborations with the Internet Corporation for Assigned Names and Numbers (ICANN), Internet Assigned Numbers Authority (IANA) and National Telecommunications and Information Administration (NTIA).
As I mentioned in my previous blog post, the root zone originally used a 1024-bit RSA key for zone signing. In recent years the internet community transitioned away from keys of this size for SSL and there has been pressure to also move away from 1024-bit RSA keys for DNSSEC. Internally, we began discussing the root Zone Signing Key (ZSK) length increase in 2014. However, another important root zone change was looming on the horizon: changing the Key Signing Key (KSK).
A few months ago I published a blog post about Verisign’s plans to increase the strength of the Zone Signing Key (ZSK) for the root zone. I’m pleased to provide this update that we have started the process to pre-publish a 2048-bit ZSK in the root zone for the first time on Sept. 20. Following that, we will publish root zones with the larger key on Oct. 1, 2016.
To help understand how we arrived at this point, let’s take a look back.
One of the most interesting and important changes to the internet’s domain name system (DNS) has been the introduction of the DNS Security Extensions (DNSSEC). These protocol extensions are designed to provide origin authentication for DNS data. In other words, when DNS data is digitally signed using DNSSEC, authenticity can be validated and any modifications detected.
A major milestone was achieved in mid-2010 when Verisign and the Internet Corporation for Assigned Names and Numbers (ICANN), in cooperation with the U.S. Department of Commerce, successfully deployed DNSSEC for the root zone. Following that point in time, it became possible for DNS resolvers and applications to validate signed DNS records using a single root zone trust anchor.
DNSSEC works by forming a chain-of-trust between the root (i.e., the aforementioned trust anchor) and a leaf node. If every node between the root and the leaf is properly signed, the leaf data is validated. However, as is generally the case with digital (and even physical) security, the chain is only as strong as its weakest link.
To strengthen the chain at the top of the DNS, Verisign is working to increase the strength of the root zone’s Zone Signing Key (ZSK), which is currently 1024-bit RSA, and will sign the root zone with 2048-bit RSA keys beginning Oct. 1, 2016.
Earlier this year, I wrote about a recent enhancement to privacy in the Domain Name System (DNS) called qname-minimization. Following the principle of minimum disclosure, this enhancement reduces the information content of a DNS query to the minimum necessary to get either an authoritative response from a name server, or a referral to another name server. This is some additional text.
In typical DNS deployments, queries sent to an authoritative name server originate at a recursive name server that acts on behalf of a community of users, for instance, employees at a company or subscribers at an Internet Service Provider (ISP). A recursive name server maintains a cache of previous responses, and only sends queries to an authoritative name server when it doesn’t have a recent response in its cache. As a result, DNS query traffic from a recursive name server to an authoritative name server corresponds to samples of a community’s browsing patterns. Therefore, qname-minimization may be an adequate starting point to address privacy concerns for these exchanges, both in terms of information available to outside parties and to the authoritative name server.
Perceptions can be difficult to change. People see the world through the lens of their own experiences and desires, and new ideas can be difficult to assimilate. Such is the case with the registration ecosystem. Today’s operational models exist because of decisions made over time, but the assumptions that were used to support those decisions can (and should) be continuously challenged to ensure that they are addressing today’s realities. Are we ready to challenge assumptions? Can the operators of registration services do things differently?
Do we already have strong security protections for our Internet services? For many years now, we have had numerous cryptographically enhanced protocols. Standards and suites like S/MIME, Transport Layer Security (TLS), IP Security (IPSec), OpenPGP, and many others have been mature for years, have offered us a range of protections and have been implemented by a wealth of code. Indeed, based on these protections, we already count on having “secure” eCommerce transactions, secure point-to-point phone calls that our neighbors can’t listen in on, secure Virtual Private Networks (VPN) that let us remotely connect to our internal enterprise networks, etc. However, our Internet security protocols have all excluded a very important step from their security analyses; none of them describe a crucial step called secure key learning. That is, before we can encrypt data or verify signatures, how does someone bootstrap and learn what cryptographic keys are needed? In lieu of a way to do this, we have traditionally prefaced the security protections from these protocols with techniques like Out of Band (OOB) key learning (learning keys in an unspecified way) or Trust on First Use (ToFU) key learning (just accepting whatever keys are found first), and each protocol must do this separately (and potentially in its own, different, way). This is because the protocols we use for protections have not formally specified a standardized way to securely bootstrap protocols.