Thanks, great question!

In short: I got obsessed by making it as fast as possible and read a ton of elliptic curve cryptography papers.

It was a journey that started from reading WireGuard kernel sources, then I was thinking about deriving IPv6 address from peer key, left a random comment on a dated gist https://gist.github.com/artizirk/c91e4f8c237dec07e3ad1b286f1... from which I learned about vanity key concept.

I naturally enjoy doing performance optimization work so when I discovered incremental approach idea here https://github.com/warner/wireguard-vanity-address/pull/15 I decided to create my own tool.

I've implemented first version of https://github.com/AlexanderYastrebov/wireguard-vanity-key and then continuously profiled it to improve performance. From profiling I saw that field inversion and multiplication are the main operations.

I realized I need to reduce unnecessary computation to make it faster and for that I need to understand the underlying math which is actually quite simple.

I read RFCs for Curve25519 and papers from D. J. Bernstein who invented it.

You can see how my understanding evolved from the commit history https://github.com/AlexanderYastrebov/wireguard-vanity-key/c...

Once I have the fastest algorithm to generate vanity Curve25519 keypairs I can apply it to other things that use Curve25519 (https://ianix.com/pub/curve25519-deployment.html) or Ed25519 (https://ianix.com/pub/ed25519-deployment.html) which is an equivalent curve.

See also my other related projects: * [age-vanity-keygen](https://github.com/AlexanderYastrebov/age-vanity-keygen) — Fast vanity age X25519 identity generator. * [vanity25519](https://github.com/AlexanderYastrebov/vanity25519) — Efficient Curve25519 vanity key generator.

Just checked `mkp224o` has multiple filters feature.

Prefix check is a fast operation compared to candidate key generation so checking several prefixes adds a small overhead compared to checking just one.

Wildcard support has low value for the use case in my opinion, compare:

    helloyebjctfjivalxn343gppksrzdpm33qzmeeq4qnqwgrgqy75zoqd.onion
    qbtlzwabvvkvmogjy2wdvnn6gq55463jhellobwtnjsinvtxsur67oad.onion