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Symmetric Key Encryption & Quantum Computers

COMP315 Lectures

AES

AES has the following pros:

  • Very fast to compute.
  • Key size is very small for equivalent security (265 bits vs 4096 for RSA).

Due to it’s speed, AES is used under TLS for HTTPS.

Public key encryption is often used for key sharing in symmetric encryption systems (DH for TLS). This is due to the fact that symmetric keys can’t be shared in plaintext.

Quantum Computing

With quantum computing, solving asymmetric (public key) will become feasible. This includes RSA and elliptic curve encryption.

Existing symmetric encryption is believed to be as secure as with classical computers.

This is an issue as symmetric encryption often uses public key for sharing keys. Therefore existing communications could be decrypted.

Solutions

  • Use quantum-proof cryptography.
  • Use very large key-sizes.
  • Think about how long something should remain secret.