A Tricky Path to Quantum-Safe Encryption

On August 11, the National Security Agency updated an obscure page on its website with an announcement that it plans to shift the encryption of government and military data away from current cryptographic schemes to new ones, yet to be determined, that can resist an attack by quantum computers.

“It is now clear that current Internet security measures and the cryptography behind them will not withstand the new computational capabilities that quantum computers will bring,” NSA spokesperson Vanee’ Vines stated in an email, confirming the change. “NSA’s mission to protect critical national security systems requires the agency to anticipate such developments.”

Quantum computers, once seen as a remote theoretical possibility, are now widely expected to work within five to 30 years. By exploiting the probabilistic rules of quantum physics, the devices could decrypt most of the world’s “secure” data, from NSA secrets to bank records to email passwords. Aware of this looming threat, cryptographers have been racing to develop “quantum-resistant” schemes efficient enough for widespread use.

The most promising schemes are believed to be those based on the mathematics of lattices — multidimensional, repeating grids of points. These schemes depend on how hard it is to find information that is hidden in a lattice with hundreds of spatial dimensions, unless you know the secret route.

But last October, cryptographers at the Government Communications Headquarters (GCHQ), Britain’s electronic surveillance agency, posted an enigmatic paper online that called into question the security of some of the most efficient lattice-based schemes. The findings hinted that vulnerabilities had crept in during a decade-long push for ever-greater efficiency. As cryptographers simplified the underlying lattices on which their schemes were based, they rendered the schemes more susceptible to attack...


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