When implementing a PRNG, you can make its seed as big as you want. There is no mathematical law that dictates or limits the size of a seed.

But I assume the GGP assumes that the author is lazy and used a public available PRNG instead of a custom made. (A long time ago someone broke the login security check in HN using a trick like that. Obviously, it's already fixed.)

I mean sure you could in theory, but in practice that's not how common built-in random number generators work.

I was responding to:

> chances are the length of the seed is equal to the length of the original file

And why would the chances be that? You'd really have to go out of your way for that. I don't even know if there are libraries that can handle a seed and state length on the scale of megabytes. No, chances are 99.99+% it used a seed of a few bytes, because that's how common random number generators designed for efficiency work.