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RSAC panel debates confidence in post-quantum cryptography

The Cryptographers' Panel at RSAC offered opinions on their confidence in PQC following the release of a paper questioning lattice-based encryption's viability.

Lattice-based cryptography is a proposed answer to the post-quantum cryptography dilemma, but a recently published paper cast doubt on this theory. While it appears to be a false alarm, experts were left questioning their confidence in PQC efforts.

Shanghai researcher Yilei Chen claimed in April 2024 to be able to use a quantum computer to find the shortest vectors in a lattice in polynomial time -- a discovery that could have rendered lattice-based cryptography inefficient.

This naturally rattled the quantum industry because many of the algorithms NIST is evaluating are lattice-based. Experts converged quickly to examine Chen's paper for legitimacy, however, and soon found an error.

At RSA Conference 2024's Cryptographers' Panel, leaders in the field discussed the paper and whether it lowered their confidence in the PQC algorithms NIST might standardize by the end of summer.

Confidence levels of PQC now

Adi Shamir, co-creator of the RSA algorithm and Borman professor of computer science at the Weizmann Institute in Israel, said researchers aren't yet sure if the paper's error can be solved or if it will indeed result in lattice-based cryptography being vulnerable. The event has, however, left people questioning the PQC algorithms expected to be standardized soon.

Tal Rabin, senior principal applied scientist at AWS and professor at the University of Pennsylvania, implored the industry to continue to look for PQC solutions as it continues to test whether proposed algorithms can withstand attacks.

"We may need to examine new assumptions that we can build things on," Rabin said. In some ways, assumptions are a social belief system, she said, adding that the cryptographic assumption is that PQC algorithms are considered reasonably secure and the longer they remain so, trust in them increases.

Craig Gentry, CTO at cybersecurity vendor TripleBlind, said he felt more optimistic about PQC because the error in the paper showed there currently isn't a viable attack method. "We're back to the status quo and should proceed with the post-quantum secure cryptosystems that NIST has standardized," he said.

Debbie Taylor Moore, vice president and senior partner of cybersecurity at IBM Consulting, added she felt there was no need to panic because so many people continue to offer input on PQC.

Rabin partially agreed but said the fact that it took eight days to find an error in Chen's paper has lit a fire under people to increase testing of the NIST PQC algorithms just in case.

Considerations for PQC encryption now

Despite the fact that quantum computing might not be ready for prime time for another five to 10 years, C-suites should continue -- or start -- developing their post-quantum migration efforts, Moore said.

A key component of this is how companies can protect their data now. A major worry is that attackers harvest encrypted data now and crack it later using PQC algorithms.

Whitfield Diffie, co-creator of Diffie-Hellman key exchange, ForMemRS and honorary fellow at Gonville and Caius College, Cambridge, said he understands the worry about data harvesting in particular and that he has heard complaints about it at another conference he attended. But, he added, "I don't think there's any good in panicking."

To counter the issue, Rabin recommended adopting a multilayer, hybrid cryptographic approach of using PQC alongside current algorithms, such as RSA and other public-key methods, to strengthen encryption. Apple did this in February 2024 when it announced PQ3, a PQC protocol for iMessage that offers a hybrid method to secure encrypted data against both future quantum computing attacks and current data harvesting efforts.

The experts also recommended organizations stop using public-key cryptography for data that needs to remain encrypted for longer than a decade from now. "If you have secrets you want to protect for 100 years, don't use any public-key cryptosystem -- not the new generation or old generation. Just use secret key cryptography," Shamir said.

Kyle Johnson is technology editor for TechTarget Security.

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