verifying an MD5 sum makes sure that the file in question downloaded correctly and in its entirety. losing your connection during the download or a corrupt version of the file will generate a different MD5 than that of the original upload. trying to load a corrupt ROM file could cause some very serious issues, so it is always best to make sure they match.

hope that clears it up for you!

 

the md5 should be provided by the developer/uploader of any rom. to check it on your phone, open astro, navigate to the file, long press it and select "details". to check it on your computer download a checksum utility such as this, although there are many others.

 

Guys,

Sorry I didn't see this thread earlier...it certainly is a very good idea to check validate your checksums for any file you might flash, either with fastboot or via ClockworkMod custom recovery.

ClockworkMod does not, by default, verify the signatures or that a file has a signature prior to flashing. You can use the "toggle signature verification" in CWM, but, in my opinion, signature verification should be ON by default and not OFF.

Not having previously verified either a checksum (such as an MD5 or SHA1) or performing signature verification means that you could end-up flashing a partial or corrupted file (that can't be good, right ).

I had a set of stock GNex image files on my PC last weekend that turned-out were partial downloads...that was the weekend I spent flashing back to stock about 8 times. Thankfully, I double-checked the MD5s before trying to flash them.

There is one other option you have for files that are signed (this means that there is checksum information built-in to the .zip archive itself that can be verified without you explicitly comparing them). Application .apk files are signed, so are (usually) custom ROM .zip files, as well as .jar files.

My AFV app has an option, Verify Jar-type File, that can check to see if a file is whole and uncorrupt without you having to know (and compare) the MD5 (or SHA1) checksums. It also has a function for verifying the checksums of your Nandroid backups (as well as a few others ).

Please let me know if you have any other questions.

Cheers!