This question has been burning in the back of my head for the past few days, and a quick Google search doesn't yield any usable results.

As the title suggests: What is the easiest-to-understand post-quantum asymmetric cryptographic algorithm that currently exists (as of 10 May 2021) for key exchange?

To establish common ground, assume that I understand everything from Khan Academy's Math Syllabus. On top of that, assume that I have gone through all of the undergraduate courses for MIT's Electrical Engineering & Computer Science courses.


1 Answer 1


There is only one paper I know of which explains a post-quantum key exchange algorithm in such a way that a beginner could understand it, and that is for SIDH (Supersingular Isogeny Diffie-Hellman key exchange). The paper is called Supersingular isogeny key exchange for beginners.

Abstract. This is an informal tutorial on the supersingular isogeny Diffie-Hellman protocol aimed at non-isogenists.

Note that SIDH has been badly broken, so it may not be fair to use it as an example.

If you don't care whether or not it is actually usable, then there's pqRSA which is essentially just regular RSA with (completely impractical) parameters that make it post-quantum secure.

  • 2
    $\begingroup$ “Post-quantum RSA is not what one would call lightweight cryptography: thecost of each new encryption or decryption is on the scale of $1 of computer time,many orders of magnitude more expensive than pre-quantum RSA.” If he's not being hyperbolic here, does he really mean a straight ~week of processing on a CPU less than 10 years old? $\endgroup$ May 10, 2021 at 4:56
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    $\begingroup$ @JamesTheAwesomeDude Yes he does. See crypto.stackexchange.com/q/59591/54184 $\endgroup$
    – forest
    May 10, 2021 at 20:13

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