Encryption Web.config sections
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I have read about aspnet_regiis for encrypting web.config sections in an ASP.net project, but I am confused how this works since the decryption key must live in plaintext on the actual server somewhere.

I would ideally like to use AES for encryption, but this requires adding the aes key to the web.config in plaintext itself, which seems useless to me. (from http://stackoverflow.com/a/8777147)

Perhaps I am missing something.. can someone explain how this encryption process is actually secure?