Quantum computers could break encryption. The US government is trying to prevent that.

Encryption is an important part of keeping our digital lives private. For the most part, it works well. However, new generations of quantum computers could threaten to decode the algorithms that the modern encryption process relies on.  

Earlier this week, the US Department of Commerce’s National Institute of Standards and Technology (NIST) announced the selection of four encryption algorithms that will become part of the agency’s post-quantum cryptographic standard. NIST is considering additional algorithms down the line and aims to finalize this standard in the next two years. 

NIST first asked for contributions around creating and testing an encryption algorithm that could hold up against attacks from emerging (but potentially powerful) quantum computers back in 2016. “Though practical quantum computers have yet to be built, their design—which would draw upon very different scientific concepts than conventional computers—would enable them to break some of the cryptographic algorithms commonly used to protect electronic messages,” NIST said in a press release. 

Many apps and electronic services use public key cryptography systems to protect sensitive information like your digital messages or electronic banking data. Central to this method is pairs of large numbers that act as the public and private keys for decrypting the message. But to hide the keys from prying eyes, computer algorithms use these numbers in math equations that are designed to be easily solvable in one direction, but hard to reverse engineer. For example, the numbers can be multiplied together to produce massive figures that cannot be easily factored. But quantum computers are pretty efficient at factoring, making them a threat to modern security. 

[Related: IBM’s latest quantum chip breaks the elusive 100-qubit barrier]

In order to counter this, cryptographers must create algorithms that contain problems difficult even for quantum computers to solve. 

The four algorithms chosen were designed for both general encryption (where two users swap keys), as well as for authenticating digital signatures (identity verification). Traditional cryptography uses many algebraic math problems, whereas quantum cryptography tends to play with more geometric problems. One of these geometric problems is designed around lattices, which are a multidimensional grid of points that extend out in all sorts of directions. The computer has to then find close points or vectors within this lattice.

“Three of the selected algorithms are based on a family of math problems called structured lattices, while SPHINCS+ [an algorithm for digital signature verification] uses hash functions,” NIST said in the press release. “The additional four algorithms still under consideration are designed for general encryption and do not use structured lattices or hash functions in their approaches.” 

Outside of algorithms, computer scientists have been trialing ways to take advantage of the weirdness of the quantum realm to create quantum keys. In fact, quantum keys are set to undergo a real-world test on Chicago’s 124-mile quantum network.