What is MD5 Hash

In this post, I will discuss about one of the interesting cryptographic algorithm called MD5 (Message-Digest algorithm 5). This algorithm is mainly used to perform file integrity checks under most circumstances. At this point, I will not jump into the technical aspects of this algorithm, rather, will tell you about how to make use of this algorithm in your daily life.

Before I tell you about how to use MD5, I would like to share one of my recent experience which made me start using MD5 algorithm. Recently I made some significant changes and updates to my website and as obvious, I generated a complete backup of the site on my server. I downloaded this backup onto my PC and deleted the original one on the server. But after a few days something went wrong and I wanted to restore the backup that I downloaded. When I tried to restore the backup, I was shocked! The backup file that I used to restore was corrupted.

 

That means, the backup file that I downloaded onto my PC wasn’t exactly the one that was on my server. The reason is that there occurred some data loss during the download process. Yes, this data loss can happen often when a file is downloaded from the Internet. The file can be corrupted due to any of the following reasons:-

Data loss during the download process, due to instability in the Internet connection/server.
The file can be tampered due to virus infections or
Due to Hacker attacks.

So, whenever you download any valuable data from the Internet, it is completely necessary that you check the integrity of the downloaded file. That is, you need to ensure that the downloaded file is exactly the same as that of the original one. In this scenario, the MD5 hash can become handy. All you have to do is generate MD5 hash (or MD5 check-sum) for the intended file on your server.

After you download the file onto your PC, again generate MD5 hash for the downloaded file. Compare these two hashes and if they match, that means the file is downloaded perfectly without any data loss.

A MD5 hash is nothing but a 32 digit hexadecimal number which can be something as follows:

A Sample MD5 Hash

(e4d909c290d0fb1ca068ffaddf22cbd0)

This hash is unique for every file irrespective of it’s size and type. For example, two different executable files (.exe files) with the same size will not have the same MD5 hash even though they are of same type and size. So MD5 hash can be used to uniquely identify a file.