What ecryption (if any) is used by Apple bluetooth Magic keyboard (MLA22LL/A) when communicating with MacBook-Pro?

The only real encryption it offers is the fact that it pairs with your computer based on a code you only see on your computer. There are wireless keyboards with much more sophisticated encryption such as AES. Interestingly enough Apple uses AES encryption for its Disk Utility images that are encrypted.

When using a Windows keyboard, you won't get the same start sequence keyboard strokes, and the placement of the Alt and Windows key are in reverse order of the functionality on the Mac keyboard. Many start sequence shortcuts only work on wired Apple compatible keyboards. Logitech and MacAlly are third party Apple compatible keyboards. Microsoft for its own keyboards makes a driver that will put the placement of the Alt and Windows key in the right order.

Alt=Apple's Option key.

Windows= Apple's Command key.