>The 1024-bit length is even considered unsafe. Sure in that national level entities could in theory crack 1024 RSA. They would be stupid to tie up such a valuable resource for a year or so on breaking a single SSH connection. They would instead use it on something that got them thousands or even millions of connections. >If it has 3072 or 4096-bit length, then you’re good. Less than that, you probably want to upgrad…
it is above all a question of prudence.. There are a lot of cryptographs working on the question of size of cryptographic keys and behind all the recommendations.
If you have a doubt, use this: https://www.keylength.com/en/
And use the primitives advised by the organization you trust the most