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starfiretbt's picture
Joined: 2014 Mar 15
What are md5 files

I was curious about md5 files. I've been seeing them lately on some games.

1. What are they?
2. Do I need them?
3. What do I do with them?


MikeTomTom's picture
Joined: 2009 Dec 7

What are they?

They are a checksum of the file uploaded to the MG, which you can match for data integrity against the file you downloaded. If they don't match, then something is wrong with the file, for some reason.

Do you need them? They aren't required for using the file you download. Their only use is for checking what you've downloaded, matches what's here on the server.

See Wikipedia article for more info on MD5 (message digests).

m68k's picture
Joined: 2016 Dec 30

In the old days of dial up based Internet connections there was little error checking done, as the handshake info required for that was often skipped, to reduce data traffic. So it happened quite often that a "successful" download actually resulted in a corrupted file and absent of any integrity checking by the operating system's program loader, you could truly mess up your system with such a bad executable.

Thus they invented checksums to verify the integrity of downloaded files and "md5" is just one of different versions of such "proofing techniques". Its basically a mathematical combination of a file's length and a numeric representation of its digital content. Different checksum mechanism offer varying degrees of reliabillity, which became important later on, when these numbers were used to detect alterations by viruses or malicious "man-in-the-middle" attacks. Some viruses managed to fool anti-malware programs, which relied on checksum databases, to target their attack mechanisms to exploit the weaknesses of certain checksum algorithms.