Signs message using private and public key pair. The buffered version is used to sign very long message such as whole file.
Note that signing is two step process, so you will need to run your file through the buffer twice.
Buffered sign goes like:
1. BufferedSign.
2. buffer.Update in chunks as often as needed until your through the file.
3. buffer.FirstRoundFinal.
4. buffer.Update in chunks as often as needed until your through the file (2nd round).
5. buffer.SecondRoundFinal.