It sometimes feels like we've been talking about quantum computing for decades. But last month finally brought an announcement that promises to bring the age of quantum computing an undeniable step nearer to reality: The National Institute of Standards and Technology (NIST) is ready to announce the first post-quantum cryptography standard. Nearly.
What does the news from NIST portend? Here are four issues to watch.
Issue 1: Defining a Standard
To its credit, NIST has long been conscious of the need for cryptographic algorithms that can stand up to attacks by quantum computers. More than three years ago, the Institute launched a program that invited proposals for just this kind of algorithm. Since then, there have been several rounds of selection in which the original 69 submissions were narrowed to 15. NIST then began its most recent round, aimed at providing a small subset of these algorithms forming a standard for organizations that are seeking post-quantum protection.
Once these candidates are chosen, NIST will also standardize the way that the algorithms should be implemented on a variety of systems. Standardization is important, because it will allow organizations to get sufficiently powerful encryption schemes in place ahead of the time they need them.
To see the value of this, you only have to look at the failings of the rollout of previous encryption standards. For example, in the recent rush to work from home in the wake of COVID-19, many system administrators belatedly underestimated the compatibility issues caused by manufacturers’ varying encryption protocols, leading to subsequent security problems for work-from-home networks. The problems run deep.
Issue 2: A Variety of Approaches
NIST should be applauded for getting ahead of the need for post-quantum encryption. The results of the most recent selection round, in which the number of candidates was reduced and "tracked" into two groups, can be found in the Status Report on the Second Round of the NIST Post-Quantum Cryptography Standardization Process (NISTIR 8309). NIST is asking experts to provide input on the algorithms contained there.
It appears, in its selection, that NIST is attempting to perform a complex balancing act. On one hand, post-quantum encryption needs to be standardized enough so that engineers can easily work on multiple systems. On the other hand, and as NIST has explicitly said, "It's important for the eventual standard to offer multiple avenues to encryption, in case somebody manages to break one of them down the road."
Developing a standard for quantum cryptography now is also an attempt to head off some of the issues that have been seen in the development and adoption of more "traditional" cryptographic approaches. At the moment, cryptographic practice is poorly standardized, and a wide range of encryption protocols are in use across the range of consumer-level cybersecurity tools. In this context, it appears that NIST wants quantum cryptography to be standardized before it attains widespread adoption.
As a result of this approach, the list of potential approaches has long been narrowed down to algorithms that fall into three "families" of mathematical approaches. This variety is necessary because cryptographic algorithms protect data in a variety of different ways, and the range of their application is only likely to increase over the coming decades.
The eventual goal of the program is to produce a recommendation for just two or three algorithms that would be secure against attack from quantum computers. One can be used for key exchange, in order to improve the PKI system. Others will be used to provide electronic signatures for documents, and to encrypt resting data.
Issue 3: An Uncertain Future
While NIST should be given credit for a cautious approach, it's far from clear that the program will solve the problem of post-quantum cryptography. This is true even if we assume that the algorithms produced by the program are indeed secure against quantum computer attacks.
One way in which this kind of standardization could fail is if organizations don't put sufficiently powerful encryption in place before quantum attacks begin. Indeed, one of the scariest future scenarios about quantum computing has long been that someone — likely a nation state, though maybe not a trustworthy one — will develop a feasible quantum computer before adequate protections have been developed against it.
Further, the development of post-quantum cryptographic standards will not protect data that has already been stolen. As we've previously pointed out, such data is already vulnerable to a "harvest and decrypt" attack, in which a hacker steals encrypted data with long-term value — Social Security numbers, military information — and sits on it until a quantum computer can crack the encryption and unlock the secrets.
Likewise, it's quite possible that many connected devices with long useful lives — including cars and smart sensors being designed today — will still be in use when quantum computers are widespread. For these reasons, the need to think about quantum-safe computing is now — and not something to kick down the road a few more years. Think about how rapidly the digital age advanced and overtook industries that did not adapt.
Issue 4: The Arms Race
Despite such alarming factors, NIST's recent news is quite welcome. While quantum-proof perfect secrecy might not ever be possible, it makes sense to prepare for tomorrow’s quantum threats before we actually face them. NIST should be given credit for taking the initiative and facing up to emerging threats before it is too late, before the next generation of cyber weapons has already been developed.