Digital Images Manipulation Safe?
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Thread: Digital Images Manipulation Safe?

  1. #1
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    Digital Images Manipulation Safe?

    Hey All,

    Just returned from a policing conference and thought that this little timbit would be interesting to you.

    The Ontario Provincial Police (OPP) are slowly going from conventional photography to digital.

    There was always the argument that digital images can be altered, lose visibility and integrity, as well as other arguments. But it seems that the Ident(ification) Team has found a product that garanties against these arguments.

    It's the Nikon D1 Series digital cameras.

    It uses .nef file format (which seems to be a nikon only format) which after snapshot is taken, cannot be altered. That's right, the original image/snapshot from the Nikon camera cannot be altered (kinda like a negative).

    Afterwards, for printing purpose, the police convert the image to both .tiff and .jpg. All original files are placed onto cd and stored in the evidence room/storage.

    Here are two examples of the D1 Nikon series
    D1 H
    D1 X

    Now that sounds great and all but is that possible? Can the file remain write-protected? Since it is a nikon extension (.nef) which appears to only be view by their software (Nikon View x Software (x = version)) as well as having to install a plug-in to (I'm guessing) view the files. Does this make the "original" file safe?

    Somehow, I can't believe it. If there is a will, there's a way, no? Would you think that if someone could create a program that reads the .nef files using the plug-in they could somehow manipulate the images and save the changes to the .nef files? Or create a plug-in with changes to the reading code, making the .nef file modifiable?

    I'm curious to know, that if it could happen, to ensure or not if these images could in fact be discredited in court. I'd hate to have something discovered about how to modify these files and word getting out during a HUGE court case where the evidence was photographed by a Nikon cam and the images are in question. (Get what I mean?)

    P.S. Here's a link to images from the Nikon D100 (sister to the D1 series) using the .nef to show quality of images (in .jpg) and explain the conversion sequence from .nef to .jpg
    Link

  2. #2
    Senior Member cwk9's Avatar
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    Sounds like the .nef is just an encrypted image. But if itís encrypted then its needs a key of some sorts so were would that come from. Storing the key in the program or the file doesnít sound so great so maybe you need to type in a password to view it. Maybe doesnít even use encryption, maybe it just uses a checksum but that would be fairly weak. If it is encryption I guess it would depend on how strong the encryption is.
    Its not software piracy. Iím just making multiple off site backups.

  3. #3
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    Somehow, I wouldn't think it's an encryption.
    While talking with the Ident Officer, he mentioned nothing about having to use passwords.
    (would have been a good point to give as a security argument)

    I'm thinking that it has to do with the plug-in.
    It seems that the computer requires the plug-in installed to view and copy the .nef files.

    It might be a checksum, but I'm not quite sure....

  4. #4
    Leftie Linux Lover the_JinX's Avatar
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    I'd like to go with:

    Originally posted here by cwk9
    maybe it just uses a checksum but that would be fairly weak.
    That would be a simple (but breakable) solution.

    http://freshmeat.net/projects/denef/ has a gnu-gpl nef decryptor.. now to find / make a encryptor...

    http://www.bibblelabs.com/ or http://www.ddisoftware.com/qimage/ this is a potential possibility, have to check soon to see if it saves the nef's too.





    source: http://www.nikond1.net/ and http://www.google.com
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  5. #5
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    Presumably the camera adds a nikon-only digital signature to the .nef file, which means that the nef decoding software is capable of detecting a modified file and rejecting it as having been tampered with.

    However in order for nikon to do this, the camera must have the private key stored in it iself. Now it's possible that nikon use a custom chip which signs the .nefs in hardware, and stores the private key in a non-readable format (presumably it is factory programmed, then there is no way to read it back) (like in a smart card)

    These roms in smart cards cannot be read out by any known technique (obviously some governments may have discovered a classified method), so are very secure.

    Or they may have been sloppy and the key may in fact just be in ROM or flash in the camera, in which case a fairly proficient adversary could disassemble the camera's software, find the private key and steal it (as has been done in dvd players?)

    Then you have to consider the trustworthyness of Nikon employees who have had access to the key, and potential pressure from the Japanese government for Nikon to reveal the key to them, so they can make "authentic" tampered images for national security purposes.

  6. #6
    Leftie Linux Lover the_JinX's Avatar
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    Good point slarty,

    now to wait for firmware updates by nikon

    or perhaps disassemble a nikon or two..

    I'll be keeping my eyes open on this one
    ASCII stupid question, get a stupid ANSI.
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