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Unformatted text preview: 5. (5 points) Bob acts as a trusted user to collect information from various people. Each person sends his/her data to Bob, encrypted with Bobs public key. However, before sending the actual message, each user authenticates Bob, using a standard authentica-tion protocol. Before sending their encrypted information, each person would choose some random message R, enrypt it with Bobs public key, and send E B ( R ) to Bob. Bob is supposed to answer by applying his private key to the message received, thus sending back the value R to the given person. After verifying that Bob responded with the correct R, the person will send his/her encrypted information using Bobs public key. Explain how Oscar can obtain someone elses data in this setup, without knowing anybodys private key. (Of course Oscar knows Bobs public key.)...
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This note was uploaded on 10/07/2010 for the course C S 52475 taught by Professor Gal during the Fall '10 term at University of Texas at Austin.
- Fall '10