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Upgrade Your SSH Key to Ed25519 (2018)

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Re: Upgrade Your SSH Key to Ed25519 (2018)

#4

Post by Etheryte »

I'm not sure if I understand the reasoning here. The article says a 1024-bit RSA key is considered unsafe, but still says you should "probably want to upgrade" if you're on a 2048-bit key. Why would that be the case? The given arguments, key size, speed etc, are complete non-arguments to me as compared to going through my keys and updating them everywhere where necessary.

Re: Upgrade Your SSH Key to Ed25519 (2018)

#5

Post by latch »

Etheryte wrote: post #4

I'm not sure if I understand the reasoning here. The article says a 1024-bit RSA key is considered unsafe, but still says you should "probably want to upgrade" if you're on a 2048-bit key. Why would that be the case? The given arguments, key size, speed etc, are complete non-arguments to me as compared to going through my keys and updating them everywhere where necessary.

Create new keys and start using them for any new setup you do. If you want to do a bit more, setup the newly created keys in the 1 or 2 most critical places.

Re: Upgrade Your SSH Key to Ed25519 (2018)

#7

Post by defanor »

> If it was more than five years ago and you generated your SSH key with the default options, you probably ended up using RSA algorithm with key-size less than 2048 bits long.

It's closer to 16 years, for OpenSSH [1].

> Open up your terminal and type the following command to generate a new SSH key that uses Ed25519 algorithm:

> Generate SSH key with Ed25519 key type

That's broken in an amusing way. But speaking of broken things, gnome-keyring didn't support ECC for SSH the last time I've checked (a few years ago), and was/is breaking GPG too [2]. Then there are servers with old systems not supporting Ed25519 (it was added in OpenSSH version 6.5, just in 2014 [3]). The situation with smart card support wasn't quite clear the last I've checked, either.

Besides, ECC was thought to be more resistant to quantum computing attacks, but not anymore (and seems to be an easier target at regular key sizes, actually) [4], so it lost some of the appeal.

Ed25519 still seems nice, but perhaps one shouldn't hurry to switch to it -- especially if the software support isn't great, and/or there are other difficulties.

[1] https://www.openssh.com/txt/release-4.2

[2] https://wiki.gnupg.org/GnomeKeyring

[3] https://www.openssh.com/txt/release-6.5

[4] https://en.wikipedia.org/wiki/Elliptic-curve_cryptography#Qu...

Re: Upgrade Your SSH Key to Ed25519 (2018)

#8

Post by mhitza »

rjzzleep wrote: post #3

Was wondering if Azure ever fixed that issue of requiring RSA, but of course good ol' Microsoft doesn't support it yet: https://docs.microsoft.com/en-us/troubleshoot/azure/virtual-...

GCP didn't either last year. Not sure about Azure but on GCP it was very non obvious that you couldn't connect to the Compute instance because of a not supported key type.
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