restrictions (Alice and Bob can read file1, Charlie can only read file3, everyone can write to file 3, Bob cannot write to file1 and Charlie cannot write to file2)
2. (10 pts) Alice sends the messages below to Bob (E denotes encryption and H denotes one-way hash). List all the properties (confidentiality, integrity, non-repudiation) achieved with each approach and underline the part of the message that achieves a given property. Some messages may have invalid parts. If so, discuss which part makes no sense and why. Some messages may have unnecessary parts (e.g., an encryption or hashing that is not needed). If so, point out which parts are not needed. a. (2 pts) M, E privA (H(M)) b. (2 pts) E pubB (M), H(M) c. (2 pts) E pubA (M), E privB (H(M)) d. (2 pts) E sharedAB (M), E sharedAB (H(M)) e. (2 pts) E pubB (M), E privA (H(M)) 3. (10 pts) Basics of cryptography a. (5 pts) Alice and Bob want to talk in secret. Is it better to have a secret algorithm for them to talk or to have a public algorithm and a secret key? List pros and cons of each approach and justify your answer.
b. (5 pts) Alice and Bob have settled on using either stream or block cipher. If they
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- Spring '17
- Cryptography, pts, Alice, Cryptographic hash function, Block cipher