I'm trying to understand the security implications of encrypting an ssh key with a passphrase, and storing the passphrase in the MacOS key chain or Gnome key-ring.
As I understand it, my ssh key passphrase needs to be long to prevent offline attacks (e.g., an attacker getting access to un-encrypted backups).
The operating system key-ring is encrypted using using my login password (OSX, gnome-keyring). The password normally isn't long (compared to a passphrase) as the operating system rate limits login attempts.
If I backup both my ssh key and my key-ring, have I reduced the complexity of cracking my ssh key from guessing my passphrase to guessing my password? Since it's implemented in both Gnome and MacOS and I haven't seen any warnings about this I feel like I must be wrong, but I'm not sure why.