Short, case-insensitive string obfuscation strategy

Question

I am looking for a way to identify (i.e. encode and decode) a set of Java strings with one token. The identification should not involve DB persistence. So far I

Answer 1

Rot13 obfuscates but does not shorten. Zip shortens (usually) but does not survive the URL round trip. Encryption will not shorten, and may lengthen. Hashing shortens but is one-way. You do not have an easy problem. Base32 is case insensitive, but takes more space than Base64, which isn't. I suspect that you are going to have to drop or modify your requirements. Which requirements are most important and which least important?