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[iPhone voice recorder] How to prove the authenticity of a voice recorder file?

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[iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Archimede » Mon Sep 30, 2019 11:12 am

Dear user,
this is a very important problem.

As consultant in a legal proceedings, I have an audio file created by voice recording of Apple. The duration of this file is only 20 seconds long; there is the suspect that the original file was 30 seconds long and that the first 10 second was cutted. I should prove it. My instrument is Sonic Visualizer, due to I can see all frequency graph; and Exiftool, due to I can see all meta of file. Exiftool don’t help me (the meta of a genuine Voice file is the same of a cute file by Quick Time). The question is:

in the frequency or audio graph there is a particular characteristic / silent sort period / device “signature” / something else at the beginning of a voice file, which is present in all file produced by the recorder of iPhone?

Thank you very much!
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Hugh Robjohns » Mon Sep 30, 2019 11:32 am

I'm afraid not. I can't think of any way of proving the duration of an original file from an edited version. The metadata can easily be updated, and there is nothing in the frequency response or anything else to help.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Tim Gillett » Mon Sep 30, 2019 12:29 pm

It might be worth contacting an audio forensic specialist. Perhaps for them, the recording itself could provide clues as to the likelihood it was edited or not, or they may pick up something else in the recording that might not be obvious to a non specialist.

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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby ManFromGlass » Mon Sep 30, 2019 1:59 pm

sometimes Apple keeps an original file in the trash for up to a month before deleting it. The file possibly may be stored in the users iCloud account trash too. If the user syncs the iPhone with iTunes on another Mac it is possible there is a previous backup that can be restored to the iPhone that contains the file.

I’m no expert but perhaps these could help.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby James Perrett » Mon Sep 30, 2019 2:09 pm

Every aspect of a file can be faked so having a copy of the file tells you very little. The most likely way to tell whether the file was changed would be to find the storage device that the file was originally recorded to and then to perform a sector by sector scan in order to see if there are any other sectors that may have once been part of that file. This probably requires the services of a computer forensics expert.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby ManFromGlass » Mon Sep 30, 2019 2:27 pm

James, is it that easy to change date and time stamps on an original file? I’ve never looked into this. I assumed it’s something only a pro could do.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby James Perrett » Mon Sep 30, 2019 2:35 pm

ManFromGlass wrote:James, is it that easy to change date and time stamps on an original file? I’ve never looked into this. I assumed it’s something only a pro could do.

I've not really investigated this on modern operating systems but I'm sure that someone with the right software could do it - and there would probably be a big incentive if the matter was about to go legal.

Here's the first link that I found

https://hackernoon.com/how-to-change-a- ... 4f8f76cdf4
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby ConcertinaChap » Mon Sep 30, 2019 5:11 pm

I was about to mention touch when I saw you'd covered it in your link. It can be found on any Unix or Linux system (and of course Mac OS is a thinly disguised Unix). So changing file attributes is, unfortunately, very easy.

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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Archimede » Tue Oct 01, 2019 10:00 am

Thank all for reply, I understand that there is no solution.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby The Korff » Tue Oct 01, 2019 10:54 am

I wonder if the iOS voice recorder app does a brief fade-in at the start of recording?

If you knew exactly what kind of iPhone, iOS version and recording app were used on the original, it -might- be possible to replicate it, and then you -might- be able to compare the very start of the two files. If the recording you've got starts abruptly, say, and the replicated one has a smooth half-second fade-in, that might point to an editing artifact...
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby molecular » Tue Oct 01, 2019 11:00 am

Agree with all of the above, but there is quite a lot of potential info missing from the OP... eg what even is file format he was given? could we see screenshots of the waveform?

It's definitely true that if the file appears not to have been edited, it still might have. But that doesn't mean there aren't red flags which might indicate editing that the OP isn't aware of...

this could be as simple as metadata that doesn't match the facts of the audio? such as the timestamp being later than when the recording is supposed to have been made?

or a more convoluted example: what we might consider a total botch and the OP having a .wav file which he was told is from an original apple voice recording. Not in itself impossible but for example if they edited it in such a way as to chop the signal at a non-zero amplitude, and then saved it in some formats, then the existing file would begin at a non-zero amplitude, which would not be possible if it was an original voice recording.

In other words - you could never prove a file hasn't been edited. But there might be a whole list of things which show it has, no?

[edit: similar thoughts from the Korff while I was typing! although I don't think there is a half second fade in on voice recordings, from a brief glance at some. But maybe other examples or diff from OS to OS as you say]
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Eddy Deegan » Tue Oct 01, 2019 12:26 pm

molecular wrote:... if they edited it in such a way as to chop the signal at a non-zero amplitude, and then saved it in some formats, then the existing file would begin at a non-zero amplitude, which would not be possible if it was an original voice recording.

This crossed my mind, but will the first sample in the audio not reflect the amplitude of the material being recorded? Ie: if you hit 'record' in mid-sentence, surely that would result in a file starting at a non-zero point?
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby molecular » Tue Oct 01, 2019 6:03 pm

Eddy Deegan wrote:
molecular wrote:... if they edited it in such a way as to chop the signal at a non-zero amplitude, and then saved it in some formats, then the existing file would begin at a non-zero amplitude, which would not be possible if it was an original voice recording.

This crossed my mind, but will the first sample in the audio not reflect the amplitude of the material being recorded? Ie: if you hit 'record' in mid-sentence, surely that would result in a file starting at a non-zero point?

Not sure about wavs... it would make sense - but I dragged a few voice memos into pro tools which definitely start mid sentence and the waveforms all go out from zero to "meet up with" where the waveform would start... likewise rendered mp3s... but not edits rendered as wav... so presumably it's either something to do with the mp3 format or the way voice memos are saved (which would be more useful to the OP).
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Tim Gillett » Wed Oct 02, 2019 12:58 am

Also the true beginning of a handheld device recording can have handling noises and other clues the device was moving around such as changing clarity, comb filtering, until the sound stabilizes when the device is placed on a firm surface and left. An edited version may have removed those 'start of recording ' clues. Another sign of an edited speech recording is when words, phrases, sentences don't have the natural cadences, emphases that person has when speaking. Just one example of that in the available copy could cast doubt on its veracity as a true record. Unnatural , abrupt changes in room reverberation can be another giveaway .
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby Mike Stranks » Wed Oct 02, 2019 10:00 am

Been following this with interest....

Good edits are undetectable to the ear and don't show-up on a waveform. Someone who knows their business can make edits undetectable.

It's when you try and edit material that's very poorly recorded in the first place - situations such as TG describes - that life gets difficult and edits can be spotted.

Incidentally, Tony Benn almost always made his own recordings of interviews he gave... he knew the power of the 'slanted' edit! :)

As for editing/altering metadata... you can edit any computer data if you have the right tools. Back in the day when I was working in machine-code we used regularly to go into files and edit them at bit level! :shock:
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby ManFromGlass » Wed Oct 02, 2019 1:02 pm

Yes that’s what occurred to me, Mike. Say there was a glitch in background noise for example. But this would only help the OP if it happened in the middle of a file. No way to tell if the remaining file starts after incriminating bits are gone.
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Re: [iPhone voice recorder] How to prove the authenticity of a voice recorder file?

Postby CS70 » Wed Oct 02, 2019 2:07 pm

From a computer perspective, if your device is an iPhone and it's not jailbroken, the actual file (if it exists) may still be present on the phone solid state memory.

If you have access to it (i.e. the pin or other way to unlock the phone, it might be possible to retrieve an actual recording).

Doing so tough would likely need some Apple tools, if not help.
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