CS3730 Midterm Review

1.

List the passive attacks and active attacks

2.

List the two

basic

operations in classical cryptography.

3.

The following cipher text is encrypted by

Caesar Cipher, decrypt it and get the original plain

text.

Xfctfdvsjuz

4.

The following cipher text is encrypted by

Caesar Cipher, decrypt it and get the original plain

text.

pqxoqqlcfiifkqebmixfkqbub

5. Draw a figure to illustrate the steps in one round of DES.

6. Draw figures to illustrate the encryption procedure

in ECB, CBC, CFB,

OFB,

and CTR modes

of operations.

Which modes used in block cipher and which modes used in stream

cipher?

7.

What is the Fermat’s Theorem?

8

. Define the Euler’s Totient Function.

9

. Calculate dlog

2, 19

7

10

. Calculate

Ǿ(15)

11.

What is the Euler’s Theorem?

12

. List the messages and destinations transmitted in the Key

Distribution Scenario.

1

3

. Draw a figure to illustrate the ANSI X9.17 PRNG

14.

Proof Ǿ(pq)= Ǿ(p) Ǿ(q), p and q are prime numbers.

15. Can you recover the original message

in the CFB (Cipher Feed Back) mode

if the IV is lost

in the receiver side?

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