[jas-]

Now you have a centralized single point of failure. While the ease of use is inherently obvious with the implementation, if/when it does fail you will have to fall back to public key/password auth anyways.

[tptacek]

Centralized single points of control are a basic goal of corpsec. They trade availability for security. The alternative model of individual SSH keys is theoretically more highly available, but has many single points of security failure.

[jas-]

Please enlighten me on the ‘many single points of security failure.’

[blueflow]

Which failure mode do you mean? The CA is accessible via offline means. I can walk to it and sign me a new keypair.

[jon-wood]

What happens when the building the CA is in burns down?

[blueflow]

The CA is in a gpg-encryped secrets store (pass) and has a password on itself, so it can be backupped like normal data to an off-site location.

[BenjiWiebe]

Scan printed QR codes of your private key that you had backed up off-site.

[politician]

Ideally, k-of-n key shards, stored in safety deposit boxes.

[tomrod]

That's actually pretty brilliant.

[danuker]

Provided you keep said papers away from prying cameras in a verifiable way, that is.

For more inspiration, check out the Glacier Protocol.

https://glacierprotocol.org/

[tomrod]

Thanks for the heads up!

I wish I'd thought about this when playing with bitcoin a few months after launch and amassing an integer value larger than zero. That wallet died with the hard drive.

[xxpor]

The extreme version of this is using an HSM, and putting one in a safe deposit box.

[hamburglar]

Also, this doesn’t apply to most real scenarios (especially not “how I run my personal stuff” type scenarios), but is a fun one to contemplate: what happens when your customer has requirements that specify all keys (including root signing keys) to be rotated at a certain point in the future? Having a process for this is an interesting challenge.

[remram]

The CA is a key, not a network service.

[benlivengood]

Sign with two or three CAs, and have sshd accept any of them.