Quick-and-dirty obfuscation for strings, designed to hide URL parameters from the casual experimenter without adding too much length. A little randomness is baked in to make it look like the parameters are constantly changing, even if they're not.

Obviously this is NOT SECURE; don't rely on it for strong secrecy. A chosen-plaintext attack will recover the key, just like xor.

Only works for ASCII strings. Not Unicode-safe.