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How does DRM style encryption work, want to create a similar system.

Posted on 2011-09-11
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Last Modified: 2013-12-07
Hello,

I want to protect audio files but I want to make a similar system to DRM where the user downloads a file and then has to Activate it by entering a username and password. A encryption key is then downloaded to the clients computer. The client can then decrypt the files.

The question I have is what stops one sharing his downloaded key with all his friends? With DRM you must download a new key on each computer. How does this work?

Thanks
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Question by:vincentvanhst
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DRM usually works using a symmetric key encryption scheme aka shared secrets where the *same* private key is used for encryption and decryption. Thus, there is always a copy of the private key in memory at the time of decryption. The usual challenge is in how do you distribute that private key in a secure way.

For what you are describing above, you could wrap the symmetric key used for en/decryption of the file in a public key scheme. NB: This is basically how SSL works; you use a public key encryption scheme such as RSA to set up a secure channel and within that channel you transfer the symmetric key that you would use for the DRM
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