>>The CRC, or any hash or encryption should be done on the file contents - not the size
>
>Very well
>
>>A CRC is a hash. Since the whole file has to be read in order to calculate the hash, the longer the file the longer it takes the calculate the hash
>>
>>Note that the time is not that significant. I can encrypt ( Rijndael) at speeds of 25 to 35 MB/sec. And this is a block cipher with multiple rounds per block (10, 12 or 14) and lookup tables
>
>Ok, thanks, if I ever have to implement such detection, I will make it OS free specific.


Any hashing/encryption on a file ( = sequence of bytes ) is always OS independent