@ars42525 できたっぽいです!
10秒後に切れる鍵対をつくって、
$ cat pars.txt
Key-Type: EDDSA
Key-Curve: ed25519
Subkey-Type: ECDH
Subkey-Curve: cv25519
Name-Email: expiring@example.com
Expire-Date: seconds=10
Passphrase: passphrase
$ gpg --batch --full-generate-key pars.txt
$ gpg -K
---------
sec ed25519 2024-11-04 [SCA] [expired: 2024-11-04]
1BB275307C9E287C7162553C429133CFC62F6408
uid [ expired] expiring@example.com
有効期限を3年後くらいに延長する:
$ gpg --quick-set-expire 1BB275307C9E287C7162553C429133CFC62F6408 2027-11-01
$ gpg --quick-set-expire 1BB275307C9E287C7162553C429133CFC62F6408 2027-11-01 \*
$ gpg -K
---------
sec ed25519 2024-11-04 [SCA] [expires: 2027-11-01]
1BB275307C9E287C7162553C429133CFC62F6408
uid [ultimate] expiring@example.com