O nome de usuário é um comentário, você pode excluí-lo ou configurá-lo com a opção -C
Eu não vejo um nome de host em nenhuma parte das chaves, para qual arquivo você está olhando?
ssh-keygen -f test -C noname
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in test.
Your public key has been saved in test.pub.
The key fingerprint is:
a8:fa:78:ea:bb:c6:70:67:4c:79:ac:0d:a7:78:5a:40 noname
The key's randomart image is:
+--[ RSA 2048]----+
| |
| E |
| . o |
| . + +. |
| = B. S |
|. o O.. |
| + *. |
| +o. |
| oB*. |
+-----------------+
cat test
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,6BD3B77199F57BCD0BBC4BD4D717931C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-----END RSA PRIVATE KEY-----
cat test.pub ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC2XiZLbaRwCZFPYUMNdzL7zCRvijpd4PaEbK4 / zcXb6ns / 9Eg2URJEVIDEBbKFrNnCQU48VNjiGG4yDyrn7COHLzWKgvLjraYV8gD0MnzqE52U5L85iuuhXcgVhc0i4Jqu3k4XoUNHGqtYMZstBhS39MCD2h8bkfKuz4eycWlyfKpktd8yIJjeUsV39mw7U7 / qh / 508RGuwriYe8AYNqgivnL0PmZaDwZGTCnEFaP0IPLbqKyFTcmSuVChmTYttE1Kcj4DNI57APaq2EzSGUNrBVGSJ7Q6KbXC4xiSF + RCDy8ruOk7hj2x2MGOwBZdvhy55kmMkhUMCC7BUcSiRA9F noname
Nenhum nome de usuário ou nome de host em qualquer arquivo, teste ou test.pub