I did some quick researching:
- SHA1 hash (MiME Base 64) is calculated to each file and stored in META-INF\MANIFEST.MF
- hashes can be calculated for example with AccuHash (
http://accuhash.com/)
(Tools -> Hash Calc -> set Hash type to SHA1 -> set Encoding to MIME Base 64, select the file, calculate)
I tried to put a table.jpg in the archive, then calculated the hash and put it in MANIFEST.MF. When trying to start the client it pops up a "SHA digest error" dialog.
As I said earlier, I have no knowledge in these things, so the above info might be wrong. Hopefully someone will experiment this further.
(I actually managed to change table.jpg once... without changing the hash values or anything. Why that worked, I have no clue)