Adding DM_26 file format to custom signature

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CELEDONIO
Posts: 2
Joined: 22 Dec 2020, 15:57

Adding DM_26 file format to custom signature

#1 Post by CELEDONIO »

Hello!

I have been using Testdisk/Photorec for over a year now and it has really given me excellent results.

However, I have no advanced knowledge of programming or scripting, and I can't recover files with the extension "DM_26".

I would be eternally grateful to whoever provides me with a file/command line/script to add this extension to Photorec, or tells me in an easy way how to do it, since I can't really grasp what the tutorial explains.

Please feel free to inspect both files, Merry Christmas to all.

https://drive.google.com/file/d/1Fp3RPN ... sp=sharing
https://drive.google.com/file/d/1utkC74 ... sp=sharing

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recuperation
Posts: 1111
Joined: 04 Jan 2019, 09:48
Location: Hannover, Deutschland (Germany, Allemagne)

Re: Adding DM_26 file format to custom signature

#2 Post by recuperation »

I don't know the file format "dm_26".
I would have expected you to provide documentation on that format.

You can build yourself a signature file for "dm_26". You look at a couple of samples, not just two, at least three with a hex editor and try to find out which part of the file never changes. That is called fingerprint - you find the least common denominator file-wise.
Without a technical spec of the file format the job is guessing and trying.
With documented formats like JPEG you can read what the fingerprint has to be.
With undocumented formats you have to do trial and error.

The more specific the fingerprint is the less you get false positives but you might miss a real positive one.
If you are less specific you get more false positives but you won't miss a positive one.
That is comparable to Covid testing: A few real infections hidden under a wave of positive test results as the testing only applies to one or two parts of the virus which does not automatically imply that a fully functional virus is present.

CELEDONIO
Posts: 2
Joined: 22 Dec 2020, 15:57

Re: Adding DM_26 file format to custom signature

#3 Post by CELEDONIO »

recuperation wrote:
22 Dec 2020, 23:56
I don't know the file format "dm_26".
I would have expected you to provide documentation on that format.

You can build yourself a signature file for "dm_26". You look at a couple of samples, not just two, at least three with a hex editor and try to find out which part of the file never changes. That is called fingerprint - you find the least common denominator file-wise.
Without a technical spec of the file format the job is guessing and trying.
With documented formats like JPEG you can read what the fingerprint has to be.
With undocumented formats you have to do trial and error.

The more specific the fingerprint is the less you get false positives but you might miss a real positive one.
If you are less specific you get more false positives but you won't miss a positive one.
That is comparable to Covid testing: A few real infections hidden under a wave of positive test results as the testing only applies to one or two parts of the virus which does not automatically imply that a fully functional virus is present.
Thank you I'll give it a try

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