How to calculate checksum in information and technology

It can be done using the software like MD5 & SHA Checksum Utility and Online Checksum calculator.

Explanation:

Suppose you are downloading the ISO file the checksum will be listed. And as you download your file, you will need the checksum calculator for verifying the integrity of the file.

Around 99.9% of the cases, you are not required to care for the checksum while you download the files from the Internet. Though, if you download something sensitive such as antivirus or the complicated software such as Tor, the good habit is to verify once the checksum since the hackers can inject the malware-infested versions of that critical software for gaining complete access to your system.

Many utilities are available for calculating the checksum, but only one or two are the best ones like MD5 & SHA Checksum Utility and Online Checksum calculator.

Install the first one on your computer.

This one is quite simple and very easy for using, you just need to click on the browse button for choosing your file, and automatically the hashes will be calculated for the MD5, SHA-512, SHA-1, and SHA-256.  THE MD5 is the shortest and the SHA-512 is most in length. And the lengthier the hash, the more secure it happens to be.

For the verification of the hash, you simply need to copy and then paste it over at the hash box, which is located at the bottom. Now click on the verify and it will then compare it with the generated hashes (4 in number) to check if there is a match. If it matches you are safe.

You can also use the Online checksum calculator if you want.

We can calculate the checksum on our own as well:

We want to send 32 bit message, and hence we devide it into m parts of k bits each such that mk= total size of data sent in bit, or whatever unit used.  

10101010101010101010101010101111

Divide above in four parts:

10101010

10101010

10101010

10101111

Now add first 2 and if 1 is carry over, add it to the resultant. Go on doing this till you get the final sum. And then take 1s complement

10101010

10101010

01010100

      1

01010101

10101010

11111111

10101111

10101110

      1

10101111  take 1s complement

01010000 (checksum)

Send four original parts and checksum to receiver

At receiver end:

all four parts are added, which will be same as previous, when we added them. Now add this to checksum, and take 1st complement, ad if everything is 0. It means our data ia original, and we need not worry.

10101111

01010000

11111111 take 1s complement

00000000

All are 0 hence the file is not corrupt and the original one sent.