Technology The Integrity of Computer files

Discussion in 'Technology' started by tablet, Mar 15, 2005.

  1. tablet

    tablet Premium Member

    Every files on your computer have a finger print/signature. A highly unique signature just like we all have a unique DNA structure. The probability of both files having the same signature is very low. IF one were to change a file, one would inevitably change the signature of it as well. A name for calculating the signature of a file is called “Checksum”.

    Now on when you download software you might see something like:

    CRC32: 9F512174
    MD5: 642E44DEFE9F212BC5CF589A573BBC33
    SHA-1: 7BFD76C3B771D6B4E64C760A8A1FA495DE1EC011

    These are the finger print of a file that you’re about to download. IF you have a checksum utility and what this utility does is basically calculate the checksum of the input file. This allows you to compare with the finger print at the site that you’re downloading the file. To check the integrity or see if it has been tampered with it in anyway, to ensure that the file you’re getting is legimit.

    Suppose I have a file called “X” and it’s about 500MB and you have a file called “Y” and it’s 500MB. Both files are 500MB and it makes us think that they’re probably the same file… To be 100% sure one of us must send the file to each other and compare it, but what if you’re not on high speed (sending 500MB is a long time on low speed) ?

    The answer to that is checksum, you just send the checksum instead of the file itself. There’s a free utility, called eXpress Checksum Calculator


    [Edit to add]
    You can use this to monitor your own important file/software to see if it get infected by virus or not. All you need to do is checksum the file and save the checksum along with your program/file. Then later you can rechecksum the file and compare it with the checksum that you previously saved.