motion detection pcoded files are not encrypted, they are just obfuscated by being pre-parsed into the format which is directly used by the MATLAB execution engine, which is not human-readable. They are not a secure way of protecting your source code (though it will likely stop most people who aren t very determined). R2015b includes a new execution engine which does not work with the old pcode format - this future change was preannounced in the release notes for R2011a