This is an update to my personal notes that made up my 2016 post: SSH Key Types and Cryptogpraphy: The Short Notes.
Things have changed in short 6+ years since this post. Namely DSA is long one, RSA is on well on its way out, and the two newer options in that post are now considered the minimum standard.
The too long, didn’t read version of this entire post is almost the same as what I said in 2016 - use ed25519 for your keys unless something explicitly does not support it.
OpenSSH Version References
From the notes I gathered to make the previous blog post - ed25519 was introduced in OpenSSH 6.5+
Ubuntu
| OS Version | OpenSSH Version |
|---|---|
| 12.04 | 5.9 |
| 14.04 | 6.6 |
| 16.04 | 7.2 |
| 18.04 | 7.6 |
| 20.04 | 8.2 |
| 22.04 | 8.9 |
macOS
| OS Version | OpenSSH Version |
|---|---|
| 10.12 Sierra (2016) | 7.3 |
| 10.13 High Sierra (2017) | 7.6 |
| 10.14 Mojave (2018) | 7.9 |
| 10.15 Catalina (2019) | 7.9 |
| 11.x Big Sur (2020) | 8.1 |
| 12.x Monterey (2021) | 8.6 |
| 13.x Ventura (2022) | 9.0 |
| 14.x Sonoma (2023) | 9.3 |
Nova / Horizon (OpenStack)
Of note ed25519 support was removed prior to Ocata, and then restored with around version 19 (Stein / Apr 2019) of nova-api.