What are the QuickSFV comments at the end of an SFV file based on?
25-Monty_Python-The_End-EOS.mp3 D387716E ;Q1-1c11727069c13b6 ;Q1-///4AA==
In version 2 it had a line more:
cowiso-xvid-yrrol.part48.rar 60C3AB2E cowiso-xvid-yrrol.part49.rar E50D18BC ;Q2-1c25890ae82a640 ;Q2-8KmPHkmiwgE= ;Q2-////////gA==
SFV files have different kinds of comments depending on the tool, but only QuickSFV edits the file and stores weird information at the end. See the SFV FAQ for more information about the SFV file format.
; indicates the start of a commented line and
Q2- seems to refer to the QuickSFV major version. I looked through the version history and these are my findings so far:
v1.50b changes: A small bug was fixed when the last line of an .SFV file did not end with a CR or LF. The "Previously Checked Files" database would be tacked on to the end of that line instead of on a line by itself.
v1.51 changes: If an SFV file already has an existing DB embedded in it, QuickSFV will use it but not update it or remove it.
It's called the "Previously Checked Files" database.
v1.60 changes: A unique signature is now recorded within the Previously Checked Files database to keep track of whether the database was created by the current user or a different user. This will help when SFV file creators verify the files and leave the Previously Checked Files database in place when uploading the SFV file. This signature is simply a random number and contains no specific information to the machine it is running on. It is generated during install or if the corresponding INI setting is missing. Upgrading will maintain this signature as long as you install to the same folder as the existing version of QuickSFV. Installing to a new folder will reset this signature causing QuickSFV to ignore the Previously Checked Files database when verifying. Uninstalling QuickSFV will erase the signature.
The random number is in a quicksfv.conf file that can be found in
C:\Users\User\AppData\Local\QuickSFV for version 3 and looks like
Signature=1234567890, a 10 character number and seems to be random. Version 2 ini is located at
C:\Program Files (x86)\QuickSFV\QuickSFV.ini and contains a 15 character hex string. In the above examples, this is the first line. This line will stay the same for a system and can identify an install.
I'm not convinced that this string is still completely unique or random! Random SFV files on the internet seem to start with
1d. Maybe it is based on the timestamp of installation? For my test it started with 1d, while older files all seem to start with the other one.
After this suspicion, I got the following result from experimentation:
Signature=1d17fc36609ef78 ;Q2-1d17fc7bfca4eee ;Q2-1d17fc830b747a9
It's clearly an incrementing number. How to turn this into a date or is it something else?
v2.00 changes: Added an expiration function for the Previous Verified DB. This is an .INI setting allowing you to specify the maximum date of the DB before assuming it is old and reverifying all of the files. It defaults to no expiration, but [...] Added right-click menu option to remove all Previously Verified DB info from the current .SFV file.
The time stamp of a file is modified after changing the database. This is how this feature works.
And then there are one or two more lines to explain. What exactly do they represent? How does this database work?