Thread: Public Key Cryptography
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Old 03-27-2008, 10:46 PM   #50
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Quote:
Originally Posted by Taylor514ce View Post
anyone can see what? No one can log into my webmail and read my emails except me, unless I give away my password.
I send you encrypted email. You decrypt it. You forward it without re-encrypting it. No more protection.

Or, I send you an encrypted book. You decrypt it. You forward it without re-encrypting it. No more protection.

For example, I send you "book.txt" which is PKI encrypted with your public key. You promptly decrypt it using your private key. Now you have a copy of "book.txt", and it was sent to you using PKI. What you do with that file is entirely up to you.

Does that make more sense now?


The scenario I thought you were addressing is: Honest Bob and Dodgy Dave each buy a copy of "I Need Food" by Some P Sucker. The publisher desires to both send copies to both, and prevent them sending copies of the books to their friends.

DRM attempts to do this by locking the book to a device or a piece of software. So Dodgy Dave sends a copy of the book (and the software if necessary) to Crafty Chris, and that's fine, but when set up it does not work.

PKI helps a little with "send copies to both", in that Awful Alice can't snoop the transmission and get the book that way, since she won't talk to Dave or Bob. But Crafty Chris asks Dodgy Dave for an unencrypted copy of the book and Dodgy Dave sends it, because the PKI software is designed to make it easy for Dodgy Dave to Decrypt the Data.
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