Review your favorite Linux distribution.
Go Back > Forums > Linux Forums > Linux - Newbie
User Name
Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question? If it is not in the man pages or the how-to's this is the place!


  Search this Thread
Old 01-18-2008, 11:44 AM   #1
Registered: Jan 2008
Distribution: Windows 8.1, Debian 7
Posts: 91

Rep: Reputation: 49
MD5 Help

Hi, i`ve noticed as i browse through some Linux distro sites that some of them mention about a MD5 / MD5 Checksum hash value or something and all i`ve seemed to really learn about it is that it`s got something to do with Cryptography with a 128bit something or other, apart from that i don`t really understand.
Could anyone help me with this please?

Thanks :
Old 01-18-2008, 12:05 PM   #2
LQ Veteran
Registered: Sep 2003
Posts: 10,532
Blog Entries: 7

Rep: Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402Reputation: 2402

If you are asking for a quick howto on how to use MD5 hash that is shown at the site:

After downloading your file, use md5sum <file> to create the MD5 hash.

The output should be the same as the hash mentioned on the site. If it is not, a few things could have happened: The download itself corrupted the file (most probable) or someone tempered with the file (virus, malware etc). Guess I don't need to tell you that the file should not be used if this is the case.

If you want to know more about md5:
unofficial home of md5

Hope this helps.
Old 01-18-2008, 12:58 PM   #3
Senior Member
Registered: Mar 2004
Location: Cary, NC, USA
Distribution: Fedora, Kubuntu, RedHat, CentOS, SuSe
Posts: 1,288

Rep: Reputation: 99
It only sort of has to do with cryptography. A hash is the output of a one way function on some input. One way means that given the output, there is NO WAY to determine the input. For example, the function "input * 3" is a 2 way function. If I am given the output 6, I know the input was 2. However, the function "input mod 7" is one way. If I'm given the output 2, there is no way to know if the input was 2, 9, 16, etc. The problem with hashes is that they have what are known as collisions (the 2, 9, and 16 in this example all collide with an output of 2). ALL hashes will have collisions (otherwise they would be 2 way). The trick is to have as few collisions as possible. MD5 is a VERY complicated function that has a very limited number of collisions. This means it is almost impossible to come up with two inputs that will collide with the same output. This means that if you have a file and get an MD5 hash of that file, any other file with the same MD5 hash is almost certainly a copy of that file.



Last edited by forrestt; 01-18-2008 at 01:01 PM.


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
c++ md5 develinux Programming 2 02-28-2009 10:38 AM
difference between md5 shadow and md5 elsewhere? whysyn Linux - Security 5 12-11-2007 10:11 AM
Md5 hlinux Fedora 2 06-28-2005 10:21 PM
what is MD5... JT13 Linux - General 2 06-11-2005 06:31 PM
using iso.md5 and iso.md5.asc Tyir Linux - Newbie 3 07-10-2004 11:45 PM > Forums > Linux Forums > Linux - Newbie

All times are GMT -5. The time now is 03:52 PM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration