Cryptography Assignment

1. Decrypt the following message. Assume direct letter substitution.

blf szev yvvm z tivzg xozhh. I drhs blf zoo hfxxvhh zmw hzkkrmvhh.

2. Research the RSA cryptographic algorithm.

a. If the Public key (e, n) is (7, 33) what is the Private Key (d, n)? Show and explain your solution.

b. Can there be an interchange between the two keys? That is, can we encrypt with the Private Key and decrypt with the Public Key? Use the pair out of 2.a. To show it, one way or another.

3. The following message: 1234567890987654321234567890 produces a hashcode of 4884260. What will be the hashcode produced by the same algorithm for the following message? 2134354654789643356778532356899556463393

4. Research steganography.

a. How does steganography work (About 100 of your own words)?
b. Under what circumstances steganography can be detected?
c. Under what circumstances steganography cannot be detected? (Give an example)

5. Express the sum A + B + C in Mod 10.

A= 123 Mod 11 B= 456 Mod 13 C= 789 Mod 15

6. Give a specific example (and a reason) of data for which:

a. Confidentiality is more important than integrity.
b. Integrity is more important than confidentiality.
c. Availability is more important than confidentiality.

7. In about 100 words of your own, provide your professional recommendation for defense against cyber-ransom demands?

8. In a data system A is the number of digits per message, B is the hashcode generated for each message, where A>B. Derive an expression showing the number of messages that will have the same hashcode.

9. What is the purpose of the Diffie-Hellman algorithm? What are its major strengths and weaknesses?

10. Review document Digital Currencies on crypto currencies and in about 100 words of your own, express your concerns.