The US National Security Agency has published a discussion paper about quantum cryptography, saying it does not know “when or even if” a quantum computer will exist to “exploit” public key cryptography.

In the paper, titled Quantum Computing and Post-Quantum Cryptography FAQ, the NSA said it “has to produce requirements today for systems that will be used for many decades in the future”. With that in mind, the agency has documented (PDF) predictions for the near future of quantum computing and their impact on encryption.

Is the NSA is worried about the threat posed by a Cryptographically Relevant Quantum Computer? Apparently not.

“NSA does not know when or even if a quantum computer of sufficient size and power to exploit public key cryptography (a CRQC) will exist”, which sounds fairly conclusive – though in 2014 the agency splurged $80m looking for a quantum computer that could crack current encryption in a program titled Owning the Net, so the candour of the paper’s statements is perhaps open to debate.

Eric Trexler, VP of global governments at security shop Forcepoint, told The Register: “Progress on quantum computers has been steadily made over the past few years, and while they may not ever replace our standard, classical computing, they are very effective at solving certain problems. This includes public-key asymmetric cryptography, one of the two different types of cryptosystems in use today.”

Public-key cryptography is what the world currently relies on for encryption technologies such as TLS and SSL, which underpin the HTTPS standard used to help protect your browser data from third-party snooping.

In the NSA’s summary, a “cryptographically relevant quantum computer” would be capable of breaking asymmetric public-key cryptographic algorithms – and the absence of any such quantum computer for now is rather a relief. The post-quantum encryption industry has long sought to portray itself as an immediate threat to current encryption, as El Reg detailed in 2019.

“The current widely used cryptography and hashing algorithms are based on certain mathematical calculations taking an impractical amount of time to solve,” explained Martin Lee, a technical lead at Cisco’s Talos infosec arm. “With the advent of quantum computers, we risk that these calculations will become easy to perform, and that our cryptographic software will no longer protect systems.”

With the ability to solve more complex mathematical problems in the same amount of time, the ability to crack current encryption algorithms’ products becomes easier for nation states to achieve.

To that end, the NSA said it was working on “quantum-resistant public key” algorithms for private suppliers to the US government to use, having had its Post-Quantum Standardization Effort running since 2016. Nonetheless, the agency says there is no such algo that commercial vendors should adopt, “with the exception of stateful hash signatures for firmware”.

Smart cookie users will be glad to hear that the NSA considers AES-256 and SHA-384 “safe against attack by a large quantum computer”.

Jason Soroko, CTO of Sectigo, a vendor that advertises “quantum safe cryptography” said the NSA report wasn’t conclusive proof that current encryption algos were safe from innovation.

“Quantum computers alone do not crack public key cryptography,” he said, adding that such a beast would need to execute an implementation of Shor’s algorithm. That algo was first described in 1994 by an MIT maths professor and allows for the calculation of prime factors of very large numbers; a vital step towards speeding up the decryption of the product of current encryption algorithms.

“Work on quantum resistant cryptographic algorithms is pushing forward based on the risk that ‘Universal’ quantum computers will eventually have enough stable qubits to eventually implement Shor’s algorithm,” continued Soroko. “I think it’s important to assume that innovation in both math and engineering will potentially surprise us.”

While advances in cryptography are of more than merely academic interest to the infosec world, there is always the point that security (and data) breaches occur because of primarily human factors. Ransomware, currently the largest threat to enterprises, typically spreads because someone’s forgotten to patch or decommission a machine on a corporate network – or because somebody opens an attachment from a malicious email.

Or there’s the old joke about rubber hose cryptanalysis, referring to beating the passwords out of a captured sysadmin.

Talos’ Lee concluded: “In a world where users will divulge their passwords in return for chocolate or in response to an enticing phishing email, the risk of quantum computers might not be our biggest threat.” ®