Originally posted by: Doctor M
Good info JT.
I used Easy SFV Creator to build the checksum, but the fact is, it's the first time I had ever done anything of the sort.

I was going on the assumption that SFV was a more modern checksum than MD5.

I didn't even know what a PAR was when I did it either. PAR can do a checksum file without recovery files?

I found out about Md5, then Par from my Usenet leeching.

I've lost data in a variety of interesting ways, so I read the boring stuff that I came across, about them (as best I could).

The smallest par file <filename>.par2 is just a verification file, but QuickPar makes you create recovery files with it - you can set it to the minimum recovery percentage (seconds or minutes) & then delete the recovery one. But QuickPar doesn't do sub-folders. I wish it did, partly because it also checks its own par files for corruption. I like to make a small recovery set, of the video_ts folder (in case I get a bad spot on the disc) and stick it in the DVD-rom folder.

I've been using MKW, for md5's, but there might be better freebies floating around. (The shn and other compressions have been surpassed by flac, so it hasn't been updated for years). You can tell it to add shell extensions, so you can do all the contents and subfolders of a folder from a right-click. (To make an md5 for a dvd, with it, you'd have the video_ts, dvd-rom, and so on, as subfolders in a parent folder, and right-click on the parent). The md5 file is a lot quicker (less slow) than par, because the md5 proggie doens't have to calculate recovery data.

I've googled up bits and pieces about it - didn't find the exact page that I read before, but the same info. And that md4, then md5 were developed as upgrades to the CRC 32 method that SFV uses. CRC 32 uses a 32-bit hash, and md5 uses 128-bit. The higher bits, (and other headache-inducing details), keep it from giving a false-ok (a bigger problem with bigger files) by some ridiculously greater factor. CRC 32, then Md5 caught on in mainstream proggies. Par uses the md5 hash for its testing. (Don't ask me how par does its recovery, I think it has to do with magical pixie spells or something.