PUB400: VSCODE/Code4i works, PuTTY does not

[SJLennon]

I'm not an expert is public/private keys, but a long time ago I created .PPK keys with PuTTY. And I've been able to happily connect to PUB400 with both VSCODE/Code4i and PuTTY without needing a password.

I can still connect with Code4i, but as of Feb 16, 2026 PuTTY says "Server refused our key" and defaults to needing a password. (Which it accepts and connects.)

I haven't changed anything on my Win 11 PC, so I don't understand why PuTTY has problems with the key.

Does Code4i do something different that makes the .PPK keys work?

I tried with PuTTY in Windows CMD and found this in the log:

debug1: Trying private key: C:\Users\Sam\Documents\Sam_tech\Certs\PUB400.ppk
Load key "C:\Users\Sam\Documents\Sam_tech\Certs\PUB400.ppk": invalid format

But this same key works with Code4i. Strange...

[SJLennon]

Played around for a while without success.

Finally created new keys with PuTTY and PuTTY would connect, Code4i would not.

Used PuTTYgen to convert the .PPK key. This key works for Code4i but doesn't work for PuTTY.

So now I have two private keys, one for PuTTY and one for everything else. Both private keys work with the same public key on PUB400.

(No idea why the .PPK private key used to work with both Code4i and PuTTY, version 0.73)