What is one-time pad for encryption?
Describe how it offers both Confusion and Diffusion.
Using the letter encoding discussed in class (along with one-time pad), the cipher text, KITLKE was generated using one-time pad. What is the one time pad used if the plain text is "thrill"? What's the key if the plain text was "tiller"?
Encrypt the following plain-text using play-fair encryption scheme. Use WEDNESDAY as the key. Plain Text: "I DREAM OF RAIN"
Suppose that you have a message consisting of 1024 bits. Design method that will extend the key that is 64 bits long into a string of 1024 bits. Encryption is performed by XORing the data bits with the extended key bits. Discuss the security of this approach1. In the Diffie-Hellman algorithm for key exchange, suppose Alice sends Bob (19,

3, 5) corresponding to (p, g, g a ). Bob responds with (12). Determine the session  key.

2. Consider RSA encryption with P = 7, q = 11.

a. List four legal values for e

b. Decrypt the cipher c = 321 assuming it was encrypted using the smallest value of e from the possible values (Assume the encryption is done one digit at a time).

3. In the class, we discussed the side channel attack of deriving the private key bits over a network using selected plain texts and monitoring the time to sign the text. Describe how you will continue the attack to derive the second bit of the private key (note that in class, we discussed the derivation of only the first bit).

4. Describe the difficulties in distributing keys in resource-constrained environments such as sensor networks and RFIDs. How is this problem addressed in industry?

5. Compare the complexities of elliptic curve crypto systems with the RSA scheme.