I've seen it at least once in code from a big car manufacturer who encrypted their software or parts of it to avoid you reading the xml files. They use a key, split into two or more parts, hidden as the first bytes of some file or as plain text somewhere it would not be out of order, then recombine, run through an deobfuscation function to be an old fashioned DES or XOR key to decrypt the (usually XML, could have been a different key format it's been a while) files. It's not that uncommon. It's also security theater. Funny part is they didn't obfuscate the code to read the key.