Not sure if it is the same encryption as I lost the original. People are saying it doesn't work anymore so I rewrote it with whatever they are currently using. Works just like the old. So you drag/drop the dat file (or txt for encrypting) onto datcryptor and it will decrypt/encrypt the file. You must provide the correct key listed below otherwise it will not decrypt/encrypt properly.
Keys for patch 5253
LevExp - 4d2
Silent - 2537
MapDestination - 2537
ItemType - 2537
MagicType - 2537
Source is included in the download.