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I want to develop a tool to hide data inside mp3s, Was: "Help with a small application" (TOS #6)
PaJaRo
post Feb 16 2009, 17:35
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Hello,
I'm thinking develop an application that hides some data inside mp3's. I wrote a raw application that replaces some random bytes on the mp3 and then it reads those bytes, so you can hide some messages.
I would like to improve this, writing the info into bits instead of bytes, using only the low significant bits that are being used to represent the amplitude (I think in this way the changes of the original file will be harder to find).
I don't know anything about the mp3 specifications ( I tried to download this http://www.iso.org/iso/iso_catalogue/catal...?csnumber=22412 seems I need to pay sad.gif ), so I'll be very glad if some one can give me some tips on how to do that, know which bits change.
May be my assumptions are wrong, if so, please correct me and sorry for any incovenience.
Any other useful hints will be welcomed.

Regards.
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josefpriko
post Feb 16 2009, 18:11
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First:
You may run into some or even heavy legal problems. Mp3 is an ISO standard, however it's not free! Almost the complete technology is patented by the Fraunhofer Society and their contributors (Thomson).

Second:
The basic spec for mp3 is ISO/TEC 13818-3 (ISO/TEC JTC1/SC29/WG11 NO803).
You will find it as an zipped Word document somewhere at http://www.mp3-tech.org.
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kwanbis
post Feb 16 2009, 18:21
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Sorry, why would you want to do that? to watermark the files?


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PaJaRo
post Feb 16 2009, 19:01
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QUOTE (kwanbis @ Feb 16 2009, 18:21) *
Sorry, why would you want to do that? to watermark the files?

Different purposes: watermarking, steganography, know more about mp3 specs and practice coding.

@josefpriko Thanks for the link smile.gif I'll take a look to it later at home. About the legal problems, Is not legal to modify a mp3 with a software?
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josefpriko
post Feb 16 2009, 19:28
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QUOTE (PaJaRo @ Feb 16 2009, 19:01) *
About the legal problems, Is not legal to modify a mp3 with a software?

Of course, this is absolutely legal as long as you don't touch the "coding" itself. Furthermore, this depends on the country you live in.
At least, i'm not a lawyer though i had some training many years ago... mad.gif
smile.gif

This post has been edited by josefpriko: Feb 16 2009, 19:28
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PaJaRo
post Feb 17 2009, 14:25
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QUOTE (josefpriko @ Feb 16 2009, 18:11) *
The basic spec for mp3 is ISO/TEC 13818-3 (ISO/TEC JTC1/SC29/WG11 NO803).
You will find it as an zipped Word document somewhere at http://www.mp3-tech.org.


I couldn't find that zipped document, I can only find some info about the headers sad.gif
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josefpriko
post Feb 17 2009, 20:15
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http://www.mp3-tech.org/programmer/docs/iso13818-3.zip
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TJA
post Feb 24 2009, 18:01
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Such things are already done - since years.
Most probably patented.


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