Metal Gear Solid 2 (PS2) - encrypted header(STAGE.DAT)

[AnonBaiter]

The sample(which contains only the header) is in the attachment.

[AnonBaiter]

Sorry for necroposting, but I just wanted to know the algorithm to decrypt the header. I would've found out the algorithm just by looking at the executable, but I don't have a disassembler at the moment(and the best one at the moment(IDA Pro) costs huge amounts of money so I won't even touch it).
Besides, what's with these views when there are so little solutions aside from Solidus?

Here's the executable, by the way.