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My online store is being developed so that I can sell mp3 downloads of hypnosis sessions for home use. How do I encode the mp3's so that they can't be copied again once downloaded??

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Many people much smarter than anyone here have found no good answer to that. bradcolbow.com/archive/view/the_brads_why_drm_doesnt_work –  Ignacio Vazquez-Abrams Mar 10 '11 at 21:01
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Not sure where the downvote comes from. Protecting one's property and livelihood isn't a bad thing in itself. The user just might not yet know the technical implications (read: how much DRM actually sucks for honest, paying customers). –  Daniel Beck Mar 11 '11 at 5:18
    
There are at least two problems with this approach. Firstly: it won't work in the end because no matter how clever any DRM you implement might be, it will only delay, not halt, the progress of people who want to copy the file. Secondly: Even merely attempting this will be to the detriment of your business; the first time someone tries to copy a file they purchased from your site for legitimate reasons they will get mad and never return to your site, and tell all their friends to do the same. –  RobM Mar 12 '11 at 12:32

2 Answers 2

It's almost impossible to stop people who want to copy your audio. If their sound adapter doesn't just let them record via "what you hear" or "Stereo mix", then they can always string an audio cable between two jacks (output and input, might need two audio devices but hey) and record it in 'analog' with little to no loss of quality, and no way for DRM to stop it.

My advice would be to give up now and spend your time and energies on something more useful, and you wouldn't be the first:

In January 2007, EMI stopped publishing audio CDs with DRM, stating that "the costs of DRM do not measure up to the results." Following EMI, Sony BMG was the last publisher to abolish DRM completely, and audio CDs containing DRM are no longer released by the four record labels.

But, if you REALLY want to add DRM your audio files then you need to use something other than MP3, as 'regular' MP3 has no DRM capabilities. You'll probably want to look into WMA, or AAC.

Hope that helps...

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This is definitely the correct answer, but I urge you not to anger your customers by switching to DRM versions of other formats. People may want to use these on their MP3 players and what not, and almost none of them support DRM. Plus, it won't actually help you keep people from pirating the contents. It doesn't even make it much more difficult. Don't bother. –  Brad Mar 10 '11 at 22:21

No. What you are asking is an impossible task, something that has been attempted by many since the birth of stored audio. A computer has to read the data, so however you encrypt it it will at some point exist unencrypted - at which point it's trivial to grab it. Even if you had a perfect encryption that can't ever be copied, you can use a loopback cable, or virtual loopback, to copy the sound perfectly and re-encode it.

On the other hand, perhaps you could offer a "taster" mp3 that hypnotises people into not copying your files ;)

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