Public key cryptography is essential in securing all Internet communications. For example, the Transport Layer Security (TLS) protocol uses public key cryptography to protect every "https" web page for entering passwords or credit card numbers. However, all public key algorithms used in practice are based on mathematical problems—such as factoring, discrete logarithms, or elliptic curves—which could be broken by a quantum computer.

The field of quantum-safe cryptography, also called post-quantum or quantum-resistant cryptography, aims to construct public key cryptosystems that are believed to be secure even against quantum computers. Ongoing advancements in physics point toward the eventual construction of large-scale quantum computers. Such future devices would still be able to decrypt present-day communications, allowing anyone to decrypt data transmitted today. Thus, it is important to start developing and deploying quantum-safe cryptography now, even before quantum computers are built.

Several mathematical techniques have been proposed for constructing quantum-safe cryptosystems, including:

hash functions

error correcting codes

lattices (including the learning with errors (LWE) and related problems)

multivariate equations

supersingular elliptic curve isogenies

The goal of the Open Quantum Safe (OQS) project is to support the development and prototyping of quantum-resistant cryptography.

OQS consists of two main lines of work: liboqs, an open source C library for quantum-resistant cryptographic algorithms, and prototype integrations into protocols and applications, including the widely used OpenSSL library.

OQS is intended for prototyping and evaluating quantum-resistant cryptography. Security of proposed quantum-resistant algorithms may rapidly change as research advances, and may ultimately be completely insecure against either classical or quantum computers.

We believe that the NIST Post-Quantum Cryptography standardization project is currently the best avenue to identifying potentially quantum-resistant algorithms. OQS does not intend to "pick winners", and we strongly recommend that applications and protocols rely on the outcomes of the NIST standardization project when deploying post-quantum cryptography.