Is this an effective obfuscation technique?
It sound like you're using something like an XOR cipher to obfuscate your code.  It will appear to be encrypted, but this can still be broken by frequency analysis since the use of a constant shift means that the encryption effectively has no key.  An example of how to break a similar XOR cipher can be found here.  As @iismathwizard mentioned, decryption requires no more knowledge than the fact that XOR is in use, in the same way as as ROT13 cipher might be broken