ssh key generation takes very long sometimes

[xemwebe]

I use the following code to generate a ssh key pair:

RsaKeypair::random(rand::thread_rng(), 2048)

which takes usually a few seconds (e.g 2-5s cpu time), but sometimes much longer, e.g. up to 20s and more.
Since the time taken varies a lot, I suspect this might be due to lack of entropy, especially since the required time seems to be much longer in un-attended scenarios (e.g. automatic testing).

Is this a known (accepted?) phenomenon? Could the long duration be circumvented somehow, especially in automatic testing scenarios?

[tarcieri]

20s sounds like you're not using a --release build?

That said, RSA key generation is still known to be slow: RustCrypto/RSA#144

If you'd like faster key generation, using any of the elliptic curve keys, e.g. ECDSA/P-256 or Ed25519, should be instantaneous.

[xemwebe]

Yes indeed, the long times are only observed in debug builds? I was just observing this in my own tests.
For some reasons, I need RSA based key for compatibility, but since using --release fixes the issue, this issue could be closed, I guess.

Thanks for the fast help!

[tarcieri]

In your workspace's Cargo.toml, you can also add something like:

[profile.dev]
opt-level = 2

...which will improve the speed at which tests run.