Finds a vanity SSH ed25519 keypair. If you want your public key to contain something like pCaRR1er, run with:
$ go install github.com/pcarrier/vanity-keygen@latest
$ ~/go/bin/vanity-keygen '[pP][cC][aA][rR][rR][iI1][eE][rR]'
and wait for the program to terminate, depending on your luck
after tens of billions (>1e10) of generations in this instance,
fewer than a hundred millions (<1e8) for [Pp]ierre,
millions (1e7) for love$,
fewer than a million (<1e6) for love.
Use -threads N if you don't want to saturate all cores.
On servers, tmux is your friend. C-b z to zoom for easy copy-paste.
Assuming you saved the private key in vanity, remember to set a passphrase with:
$ ssh-keygen -p -f vanity
Alternatively, use the comment (third) field in your .pub and authorized_keys. But where's the fun in that?
This is reminiscent of bitcoin mining. Finding a SHA-256 hash with a lot of zeroes through trial and error doesn't make it any more prone to collisions. We are similarly using brute force to find a public key of a particular shape, which shouldn't make the private key any more discoverable nor its security any weaker.
Do worry about a potential capture of the program's output, and cleartext storage of the private key.
As such, don't run this on a multi-user system for a personal keypair.
At the risk of repeating myself, do not use persistent storage that's not encrypted or physically secured throughout its lifetime to buffer the program's output or store the plaintext private key (however temporarily).
Of course, don't blindly trust random strangers on the Internet.
My chunk of the code, main.go, is tiny and should make for a quick read;
go mod verify to ascertain vendor/ isn't compromised, go mod graph to explore what's there.
Not much else for me to say about your Go standard library, runtime, toolchain, OS, and hardware. Open is better. Security is hard.
According to perf top -g and Instruments.app, we're spending the majority of the time in ed25519 arithmetic,
so the rest (string manipulations, allocations, etc.) doesn't seem worth much effort.
$ vanity-keygen 'love$'
2022/07/03 23:37:04 Looking for a public key matching love$
2022/07/03 23:37:05 Generated 232,000 keypairs (231,883 Hz)
[…]
2022/07/03 23:37:43 Generated 9,697,000 keypairs (248,625 Hz)
2022/07/03 23:37:43 Public key:
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIK8qe+Hx2yvkGfoaNwv8p7IMhxk5yIofHqIsTFPrlove
2022/07/03 23:37:43 Private key:
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtz
c2gtZWQyNTUxOQAAACCvKnvh8dsr5Bn6GjcL/KeyDIcZOciKHx6iLExT65aL3gAA
AIiaywRCmssEQgAAAAtzc2gtZWQyNTUxOQAAACCvKnvh8dsr5Bn6GjcL/KeyDIcZ
OciKHx6iLExT65aL3gAAAECmP9LWUFqCvLMq8KCsCUbC+UcXHvHYDQ9y2enu4fTb
8q8qe+Hx2yvkGfoaNwv8p7IMhxk5yIofHqIsTFPrloveAAAAAAECAwQF
-----END OPENSSH PRIVATE KEY-----