Post-Quantum curl

For some TLS connections you want the secrets you exchange over them to remain private for decades to come.

So what if someone in the future produces a computer system that can crack all the common current encryption algorithms in no time and they already have past secret communications stored?

Such a possible future computer system that might do this is believed to be the quantum computer. There are early and tiny versions of such machines already in existence, but they are far from strong enough to be cracking any strong ciphers today. The question is then how long it takes until they will be able to do that, and thus for how long recorded secret communications can expect to remain secret. 10 years? 20? 30?

If there’s a capable quantum computer made available in let’s say twenty years time, our currently most common TLS ciphers are then rendered next to worthless in twenty years. If you want your communication to remain private even after the introduction of quantum computers, you need post-quantum safe algorithms for your TLS data, and you need a post-quantum curl to use those ciphers for your transfers!

Post-quantum TLS

My colleagues at wolfSSL have recently been working on making sure that the library with the same name has support for a set of ciphers that are post-quantum safe. That work has been merged into wolfSSL’s git repository and will be part of a future pending release. That “future release” is hopefully just a few weeks off now.

In association with that, we’ve also made sure that curl built with wolfSSL can take advantage of these powers. The necessary curl changes for this have landed in git and will be part of the pending curl 7.80.0 release.

Use it with curl

To make your curl transfers post-quantum safe today, all you need to do is:

  1. make sure you have a wolfSSL build and install with the proper algorithms enabled
  2. build curl from git (or wait for the 7.80.0 release) and tell it to use wolfSSL for TLS
  3. specify a post-quantum curve when you invoke curl


curl --curve SABER_LEVEL5

The success of such a TLS 1.3 handshake with a server then of course also requires that you communicate with a server that conversely also supports quantum-safe algorithms. This not terribly common yet.


The primary curl pull-request for this feature was authored by Anthony Hu.

Image by Gerd Altmann from Pixabay