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Hypothetical Situation: I have a recording which has proof that my friend is plotting to kill a a foreign ambassador. Being one who always sticks for what is right, I plan to disclose these plans. How do I prove that these files weren't edited or modified in any way??
Inspired by this post.
rahuldottech
Posted 2015-12-31T10:21:32.823
Reputation: 5 095
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I'd say the same answer as the inspiration post - you can't. Audio can be modified, the wave forms could be examined to see any particularly odd spikes in audio where something had been cut, but someone who knew what they were doing could edit audio pretty convincingly.
Audio is edited all the time in film and music and most people would never even realise it. Of course, voice is a little easier to believe as it's hard to fake someones voice, but even still with careful editing the context of things can easily be changed.
As an example - this clearly wasn't what he was actually saying or implying, but with the audio alone it seems pretty convincing.
Jonno
Posted 2015-12-31T10:21:32.823
Reputation: 18 756
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you can't proof if voice recordings are changed unleast you know very much about recording, audio and digital signal processing and even the you can't tell 100% that there has nothing been done with it.
if you don't trust the source from where/who you have gotten the recording you also shouldn't trust the recording.
thats why an audio-sample is just used as supporting evidence never as the main-evidence.
there is one thing on all digital media one can do to recognize that they may have changed this thing is called checksum or also digital signature.
it can bee used to proof that a digital media didn't change from when the author created it till an other one recives it but it can't proof that the author himselfs didn't change it.
i think the best answer will be it doesn't belong to you to proof wether the recording is orignal or not.
it is the same as if it would be a audio-tape the one who have to decide wether it is original or not are the forensic-analysts of the police and at last the jury and the judge.
as long as they all accept it as a evidence it doesn't matter if it really is a original or not.
konqui
Posted 2015-12-31T10:21:32.823
Reputation: 504
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One possibility of improving the security of an audio recording is to supplement it with video.
In a single clean shot with a clock in the background, it would be harder to fake - though still not actually impossible, see what can be done with enough money & CGI in any modern Hollywood movie… those dinosaurs are not actually there ;-)
This Simpson's extract gives a humorous view of how intent can be changed through 'judicious' editing.
Tetsujin
Posted 2015-12-31T10:21:32.823
Reputation: 22 456
From a theoretical standpoint, you could not, in that you can only disprove. only prove. That means you must look for signs of tampering, and develop a degree of confidence that the stream is unmodified. Some traces may be digital and others analog so some visible on an ociliscope, or to the ear, or to the hex editor. – Frank Thomas – 2015-12-31T10:38:08.127
With enough processing power the tampering could be made undetectable ... – DavidPostill – 2015-12-31T10:52:24.533