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.


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.

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.

  • 1
    $\begingroup$ “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? $\endgroup$ – JamesTheAwesomeDude May 10 at 4:56
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    $\begingroup$ @JamesTheAwesomeDude Yes he does. See crypto.stackexchange.com/q/59591/54184 $\endgroup$ – forest May 10 at 20:13

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