Check & compare MD5 sum of files to verify them

Have you ever downloaded a file from somewhere on the web and seen details of an MD5 check sum associated with it? And have you then wondered what on earth it means and what you're supposed to do with it?

Well, very briefly, the MD5 algorithm takes a file and calculates a unique check sum value for that file. If you have the check sum value (as posted on the website you got the file from, say), you can then test a copy of the file to ensure that the copy is not corrupt. You do this by applying the MD5 algorithm to your copy of the file and comparing the result with the original check sum. If they match, you can be pretty sure that your copy is valid. If they don't well, throw away the file and go and get a new copy.

Anyway, winMd5Sum is a neat little application from Nullriver Software that let's you calculate MD5 sum values. And as applications go, the interface couldn't be any simpler to use:

Just enter the path to the file you want to calculate an MD5 sum for and then click Calculate. Use cut and paste to enter the original MD5 sum – as provided by the file's creator – and then click Compare. winMd5Sum will tell you whether or not the check sums match!

There's not much to this application as you can see. However, it is so easy to use and so useful that it is a must have utility – especially as it is free!

MD5SUM explained

In cryptography, MD5 (Message-Digest algorithm 5) is a widely used cryptographic hash function with a 128-bit hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. However, it has been shown that MD5 is not collision resistant; as such, MD5 is not suitable for applications like SSL certificates or digital signatures that rely on this property. An MD5 hash is typically expressed as a 32-digit hexadecimal number