You don&#x27;t need quantum cryptography to defend against attacks that employ quantum computers.<p>There was an interesting talk on classical encryption algorithms that resist quantum attacks by djb and Tanja Lange at 32c3 last year, see [1,2,3].<p>TL;DR:<p>- Shor&#x27;s algorithm kills factorization-based algorithms like
RSA, DSA and including elliptic-curves-based DSA,<p>- Grover&#x27;s algorithm allows faster (O(sqrt(N) instead of O(n)) brute-force searches, which means for the same level of security, one needs to double AES key size,<p>- there exist classical encryption algorithms that have so far resisted quantum-based attacks, e.g. hash-based signatures, Goppa code-based asymmetric crypto,<p>[1] <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=6XeBvdm8vao" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=6XeBvdm8vao</a><p>[2] <a href="https:&#x2F;&#x2F;media.ccc.de&#x2F;v&#x2F;32c3-7210-pqchacks#video" rel="nofollow">https:&#x2F;&#x2F;media.ccc.de&#x2F;v&#x2F;32c3-7210-pqchacks#video</a> (in German)<p>[3] <a href="https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;privacy&#x2F;comments&#x2F;3yppbz&#x2F;post_quantum_cryptography_at_32c3&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;privacy&#x2F;comments&#x2F;3yppbz&#x2F;post_quantu...</a><p>EDIT: formatting