When running gpg-agent with the following config:
enable-ssh-support pinentry-program /usr/bin/pinentry-gnome3 debug-level expert max-cache-ttl-ssh 60
Trying to add RSA keys larger than 4159 bit yields
Could not add identity "xxxxx": agent refused operation
> $ ssh-keygen -t RSA -b 4159 -f rsa4159
Generating public/private RSA key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in rsa4159.
Your public key has been saved in rsa4159.pub.
The key fingerprint is:
SHA256:uOAsI7grbUzAUsMNJZOVwxCvyWHG6AePH3UdPnCTK/w ekampitakis@theseus
The key's randomart image is:
+---[RSA 4159]----+
| .*Xo. . +. |
| o=+= =.o |
|oo=..o.. +. |
|+=++. .+ .. |
|.+++. . S |
|. +o.. . E |
|o+o.o . |
|.o+o |
|+o |
+----[SHA256]-----+
> $ ssh-keygen -t RSA -b 4160 -f rsa4160
Generating public/private RSA key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in rsa4160.
Your public key has been saved in rsa4160.pub.
The key fingerprint is:
SHA256:PRRorBe9qS9i+TlkWAam3DIupUlBeyTKL72xx/MhK8s ekampitakis@theseus
The key's randomart image is:
+---[RSA 4160]----+
| .o . . o. |
|...+ o = .. |
|...o.+ + ..o |
| +.* o +oo |
| o O o =S.o |
| = * . + . |
| + = = . |
| ... O +.. |
| Eoo +oo |
+----[SHA256]-----+
> $ ssh-add rsa4159
Identity added: rsa4159 (ekampitakis@theseus)
> $ ssh-add rsa4160
Could not add identity "rsa4160": agent refused operation