Not sure if this is the right sub but here goes:
Could you generate a massive database by simply running every possible private key through an algorithm and saving the corresponding public key? You might not be able to target a single public key, but with a few million users wouldn’t you find a whole lot of valid key pairs? And if you were to encounter a public key that you have in your database, couldn’t you assume their identity? (database sorted by public key so that you can actually check if you have the key pair)
I assume it’s not as easy as all that, but how much storage would you need for a complete dictionary for a “conventional” algorithm.