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Communications of the ACM


Post-Quantum Cryptography

key encircled by swirling atomic particles

Credit: ArtemisDiana

Exchanges of digital information have long been protected by public-key cryptography, which lets senders encrypt their data with confidence that only the intended recipient could decrypt and read it. The recipient can freely share their public key for encryption because deducing the private key for decryption would require an impractically large calculation, such as factoring the product of two very large primes.

In the 1990s, however, mathematician Peter Shor (then at Bell Labs and successor AT&T Research, now at the Massachusetts Institute of Technology (MIT)), showed quantum computers could do factoring and compute "discrete logarithms" exponentially faster, greatly stimulating research in quantum computing. Despite billions of dollars of investment and significant experimental progress, however, quantum computers are still too small and error-prone to pose a cryptographic threat—yet. If they do succeed at scale, though, both new data and encrypted archives could become vulnerable to snooping.


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