Hacking For Beginners – Manthan Desai

2010

6. What Is MD5 Hash & How to Use It ?

In this post I will explain you about an interesting cryptographic algorithm called MD5 ( Message-Digest algorithm 5 ). Thisalgorithm is mainly used to perform file integrity checks under most circumstances. Here I will not jump into the technicalaspects of this algorithm, rather will tell you about how to make use of this algorithm in your daily life. Before I tell youabout how to use MD5, I would like to share one of my recent experience made me start using MD5 algorithm.Recently I made some significant changes and updates to my website and obvious I generated a complete backupof the site on my server. I downloaded this backup onto my PC and deleted original one on the server. But after a fewdays something went wrong and I wanted to restore the backup downloaded. When I tried to restore the backup Iwas shocked! The backup file that I used to restore was corrupted. means, the backup file that I downloaded ontomy PC wasn’t exactly the one that was on my server. The reason there occured some data loss during thedownload process. Yes, this data loss can happen often when a file is downloaded from the Internet. The file can becorrupted 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 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 ofthe downloaded file. That is you need to ensure that the downloaded file is exactly the same as that of the original one. Inthis scenario the MD5 hash can become handy. All you have to do is generate MD5 hash (or MD5 check-sum) for theintended 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 it matches then it means that the file is downloaded perfectly without any data loss.

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

A simple MD5 Hash

e4d909c290d0fb1ca068ffaddf22cbd0

This hash is unique for every file irrespective of it’s size and type. That means two .exe files with the same size will nothave the same MD5 hash even though they are of same type and size. So MD5 hash can be used to uniquely identify afile.

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