You could but you would lose the performance benefits you were seeking by encoding information into the ID. But you could also use a randomized, proprietary base64 alphabet rather than properly encrypting the ID.
XOR encryption is cheap and effective. Make the key the static string "IfYouCanReadThisYourCodeWillBreak" or something akin to that. That way, the key itself will serve as a final warning when (not if) the key gets cracked.
Symmetric encryption is computationally ~free, but most of them are conceptually complex. The purpose of encryption here isn't security, it's obfuscation in the service of dissuading people from depending on something they shouldn't, so using the absolutely simplest thing that could possibly work is a positive.
Encoding a type name into an ID is never really something I've viewed as being about performance. Think of it more like an area code, it's an essential part of the identifier that tells you how to interpret the rest of it.
