While answering Re-using SSH keys I had a question of my own, is there a limit to the number of ssh keys you can hold in ssh agents? (and/or putty pageant).

(as a test, I loaded 10 keys into my pageant and didn't seem to have an issue)


At last for the ssh-agent, the only limit is about the maximum memory available for the user or process. The keys are stored in the linked list which does not have any effective limit and all the constructs. The only counter used is int nentries;, which limits the effective amount of keys to 2 147 483 647, which is quite enough.

The limit is more in the practical usability. Once you load a lot of keys into the agent, they are send sequentially to the server (unless otherwise specially configured), which rejects after 3 or 6 public key tests (prevents the key enumeration for user). For some people, this can be also considered as a privacy issue, since the keys can be paired with, for example your github accounts.

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