A cyclic redundancy check (CRC) is a type of function that takes an input of data stream of any length and produces as output a value of a certain fixed size. The term CRC is often used to denote either the function or the function's output. A CRC can be used as a checksum to detect alteration of data during transmission or storage.
so, if you change something in the data.pak with hexeditor, the crc checksum (value) changes too, the checksum value is different than the one that the server provides and baam.. you'll get an "invalid client.. please reinstall".
so bypassing it would be kinda nice..
bypassing it would just be simulate the proper crc value so the server thinks you got the unmodified one
