[Cryptography] Asymmetric encryption analogy (vault with 2 different locks)

[Michael Kjörling]

On 13 Sep 2022 17:53 +0200, from evs20200430f at xs4all.nl (Erik van Straten (Cryptography list)):
> A couple of years ago I came up with an analogy to explain asymmetric
> encryption to lay(wo)men, based on a physical vault with two mutually
> different locks (with non-interchangeable keys): one for locking the vault,
> and the other one for unlocking.

What you posted seems way too complicated for a layperson to grasp. To
be fair, I gave up before I made it through your text...

If you want to describe asymmetric cryptography to a layperson, go
with the simple approach. Lots of people are familiar with
self-locking key-operated locks, not least in padlocks. Anyone can
lock such a padlock simply by closing it. In an ideal world, once it's
been locked, only the person with the corresponding key can unlock,
and thus open, it. (In the real world that we all inhabit, other
attack vectors exist. Those can, in part, be mitigated by selecting a
heavier-duty padlock.)

The padlock is the public key; the key to it is the secret key. You
can give someone a padlock and they can later use it to lock a
container; the container can then be passed along by untrusted parties
while the sender and recipient can both be reasonably assured that
what's inside the container can't be accessed or tampered with by
others.

This, of course, overlooks the concept of _signing_ using asymmetric
cryptography, which requires a somewhat different description, but
that doesn't (at least immediately) map to a physical vault either, so
no great loss there.

-- 
Michael Kjörling • https://michael.kjorling.se • michael at kjorling.se
 “Remember when, on the Internet, nobody cared that you were a dog?”