Quantum Encryption and Post-Quantum Cryptography


(T) Researchers have been working on quantum encryption for a long time. Quantum encryption is based on quantum key distribution (QKD). QKD algorithms can leverage well-defined quantum states (or photon polarization states) that have to be transmitted in the key distribution protocol, or quantum entanglement (entangled pairs of photons), where the encryption key comes into existence at different locations simultaneously due to measurements on the individual participants of the entangled quantum system.

The encryption key generated using QKD is generally applied to encrypt the data using a symmetric key algorithm such as AES-256. One of the great benefits of quantum encryption is that it can detect eavesdropping.

While the properties of quantum mechanics can be used to generate encryption keys, quantum computers can break classical public key encryption.

A quantum computer running the Shor’s algorithm for integer factorization can break the RSA scheme (based on integer factorization). And a variant of the Shor’s algorithm can break other schemes based on discrete logarithms such as the Diffie-Hellman and Elliptic Curve Cryptography (ECC) algorithms.

However, note that most current private key algorithms are considered to be relatively secure against attacks by quantum computers.

To mitigate the future risks of quantum computers breaking-up public key encryption, the NSA, and more recently Google, have announced various efforts for “quantum-resistant” algorithms. The NSA published a report on that subject, and Google has just announced, on a blog post, that in addition to the elliptic-curve key-exchange algorithm for Chrome connections to Google back-end servers, Google will also implement New Hope, a post-quantum key exchange algorithm.

Note that there are few start-ups working in those two fields: ID Quantique has been working on Quantum Encryption, and Post-Quantum has been working on post-quantum cryptography.

NIST Report on Post-Quantum Cryptography: NIST.IR.8105
Post-quantum key exchange – A New Hope – Erdem Alkim, Léo Ducas, Thomas Pöppelmann, and Peter Schwabe: 1092

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Categories: Cybersecurity