1. Answer the following questions briefly
a. We discussed the meet-in-the middle attack for 2DES. If we were to use a slightly different version of 2DES where 2 key encryption is done as C = D ( E (P, K1), K2), describe a meet-in-the-middle attack.
b. What is social engineering? Briefly discuss 3 different social engineering exploits to steal someone's password?
c. If you are given a hash function (say SHA-1), design one-time password scheme for access control to your server. (Hint: You should specify details on how you will generate the passwords maintain them)
d. Describe a covert channel? Give an example and comment on the speed of the covert channel in your example.
e. As we discussed in class, early implementations of RSA, used a common e= 3. What was the security limitation of this choice? Instead, if one were to fix a common d =3 what is the security implication?
2. Consider the Elliptic curve
E: y2 = x3 + 11x + 19 (mod 167)
Suppose E and point P (2, 7) are used for ECC Diffie-Hellman key exchange.
Alice chooses the secret value A = 12 and Bob chooses the secret value B = 31.
a. What value will Alice send to Bob?
b. What does Bob send to Alice?
c. What is the shared secret at the end of the exchange?
3. For this problem you need to run MD5. You may either download a certified version of MD5 or use web-based MD5 services. You should specify what you used; for example, give the URL.
You are given a sentence "Your_Last_Name" loved 7339
a. Generate a hash for the above sentence by selecting the last 4 bits from the MD5 hash
b. Perform a birth-day attack to change the sentence to "Your_Last_Name" hated 7339
4. You are given a password file containing 64 random passwords each of which are 6 characters long where each character can assume 128 different values.
If you were to attack this password file, what is the complexity of attack for the following scenarios:
a. Brute force attack to find Alice's password
b. Brute force attack to find somebody's password
c. Attack to find Alice's password with a dictionary containing 1024 chosen passwords
d. Attack to find any password with the same dictionary