NIST has developed a chip that reliably emits a single photon on demand. This ability will improve the efficiency of QKD (quantum key distribution) as we prepare for the arrival of quantum computers.
Quantum computers will upend current cryptology by using Shor’s algorithm to rapidly negate the current public/private key secure encryption methods. This has largely been solved by NIST’s post quantum cryptology (PQC) algorithms.
Knowledge of this future is driving the ‘harvest now, decrypt later’ spate of data exfiltration – companies may not even know their encrypted data has been stolen. But adversaries, including, if not primarily, nation state adversaries, are storing that data knowing they will be able to decrypt it in the future; and who knows how many vital secrets may be within it?
The arrival of quantum computing is future, but the threat is current. Commercial and federal organizations need to protect against quantum computing decryption now.
Various new mathematical approaches have been developed for PQC, but while they may be theoretically secure, they are not provably secure (what can be made by math can be unmade by math given enough compute power, and what is sent over traditional channels can be silently intercepted).
Ultimately, the only provably secure key distribution must be based on physics rather than math. A physics solution based on photons could rely on quantum principles – for example, you can know a quantum particle exists but not simultaneously where it is. The energy of examining a quantum particle is sufficient to disturb it.
This principle is harnessed in QKD by ultimately transmitting the key as photons within fiber channels. Any attempt to intercept the key exchange will disrupt the message and notify the receiver. “If somebody tries to observe that photon as it passes along the length of fiber,” explains John Bruggeman, consulting CISO at CBTS, “that observation will break the quantum state of the photon, and the receiver will go, ‘Oops, that key is compromised. I can’t use it. Send me another one.’”
While this basic approach is secure, it is neither efficient nor cheap. “Quantum key distribution is an expensive solution for people that have really sensitive information,” continues Bruggeman. “So, think military primarily, and some government agencies where nuclear weapons and national security are involved.”
Current implementations tend to use available dark fiber that still has leasing costs. If no dark fiber is available, new fiber would be required, potentially at high cost. Furthermore, a photon can reliably travel just 50 to 60 miles before signal attenuation and dispersion, without the use of amplifiers. This can be increased to hundreds of miles by the insertion of amplifiers, which requires cutting and splicing the fiber to allow the amplifier to sit in the optical stream. While the location of amplifiers is always heavily secured, their presence once again means that provable security is lost.
Nor are current methods of generating the photons very efficient. NIST has been working on ways to “generate single photons with near-perfect efficiency and on demand.” The process involves using ‘quantum dots’ which essentially emit a single photon when hit by a carefully shaped laser pulse. The emission of these single photons can be controlled.
Current methods use faint lasers with filters that block most photons but tend to emit photons at random times rather than on demand. “They are not very efficient because they create significant numbers of multi-photon events and zero-photon events.,” explains NIST. “And they are often not bright enough to meet the needs of emerging quantum technologies.”
NIST hasn’t researched single photon production just to aid QKD, but its success will be a great boon for QKD where absolute provable security is a necessity – especially, for example in the government and the military.
“The big advance from NIST is they are able to provide single photons at a time, as opposed to sending multiple photons,” continues Bruggeman. Single photons aren’t new, but in the past, they’ve usually been photons in a stream of photons. “So, they encode the key information on those strings, and that leads to replication. And in cryptography, you don’t want to have replication of data.”
There is currently a comfort level in this redundancy, since if one photon in the stream fails, the next one might succeed. But NIST has separately developed Superconducting Nanowire Single-Photon Detectors (SNSPDs) which would allow single photons to be reliably sent and received over longer distances – up to 600 miles.
The second big advance is that NIST can do this on a single chip, which means such chips could be in mass production by the end of next year. Traditionally, NIST develops standards and industry rapidly adopts them. While the QKD market is likely to be relatively small (limited to areas that require very strong security), separate applications will quickly follow.
The reliable production of single photons could even be used within the quantum computers themselves since some quantum computing companies use photons as qubits. Perhaps more importantly in the shorter term, single photon chips could help existing small quantum devices to network and provide early quantum computing solutions before full-scale quantum computers arrive.
Whether organizations choose to base ongoing security on PQC or QKD, that decision needs to be made now. NIST’s single photon chip will likely make QKD an option for a wider range of companies.
Related: Project Eleven Raises $20 Million for Post-Quantum Security
Related: Bill Aims to Create National Strategy for Quantum Cybersecurity Migration
Related: Cisco’s Quantum Bet: Linking Small Machines Into One Giant Quantum Computer
Related: MITRE Publishes Post-Quantum Cryptography Migration Roadmap
