Do Flash Locale Shared Objects behave like cookies?

Question

Cookies are sent to the server per each request making them a slow choice for data storage. However, what's the case with Flash's LSOs? Are they only script accessible and not sent to the server?

If it matters, I'm looking for a way to store data on the client using Flash and performance does matter here (as well as the size limits). I know that the default size limit is 100 kB for LSOs.