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Solution for Practice Final.

Originally Posted By: Erni

Team:
Erni Ali
Noel Ramirez

2.

In here, T, K is signed by Alice and then encrypted with Bob’s public key when Alice sends it. So then, Bob needs to be able to use his private key in order to decrypt his public key and then decrypt Alice’s signed T, K with Alice’s public key. After that, Bob will know that it is indeed Alice who is communicating with him.

After that, Bob needs to authenticate himself to Alice by signing T+1,K with his private key and then encrypting the signed key with Alice’s public key. In order to see this message, Alice needs to decrypt using his private key and Bob’s public key.

'''Originally Posted By: Erni''' Team: Erni Ali Noel Ramirez 2. In here, T, K is signed by Alice and then encrypted with Bob’s public key when Alice sends it. So then, Bob needs to be able to use his private key in order to decrypt his public key and then decrypt Alice’s signed T, K with Alice’s public key. After that, Bob will know that it is indeed Alice who is communicating with him. After that, Bob needs to authenticate himself to Alice by signing T+1,K with his private key and then encrypting the signed key with Alice’s public key. In order to see this message, Alice needs to decrypt using his private key and Bob’s public key.

-- Solution for Practice Final

Originally Posted By: cox.michaelj6

Problem 4. Give the protocol for main mode digital signature-based IKE Phase 1.

ALICEBOB
-> IC, CP
IC, RC, g^a % p, R_A
IC, RC, E("Alice", proof_A, K)
cox.michaelj6 — Mon Dec 10, 2012 6:09 pm <hr>

'''Originally Posted By: cox.michaelj6''' Problem 4. Give the protocol for main mode digital signature-based IKE Phase 1. ALICEBOB -> IC, CP IC, RC, g^a % p, R_A IC, RC, E("Alice", proof_A, K) cox.michaelj6 — Mon Dec 10, 2012 6:09 pm <hr>

-- Solution for Practice Final

Originally Posted By: CViernes

10. What is a polymorphic worm, a metamorphic worm, a flash worm. Suggest detection/mitigation strategies for each.

A polymorphic worm is where the body of the worm is encrypted and the decryptor code is mutated before it infects the next system.
To detect polymorphic worms, we use an emulator, and the code will decrypt itself to detect the signature.

A metamorphic worm is a worm where it mutates the body of the code before it infects the system.
Can be detected by Hidden Markov Model Technique.

Flash worm is designed to infect entire Internet almost instantly.
To detect the flash worm, use Master IDS which it can slow down the flash worm because it's temporarily blocking off most of the nodes.

Christina Viernes
Kui Cheung

'''Originally Posted By: CViernes''' 10. What is a polymorphic worm, a metamorphic worm, a flash worm. Suggest detection/mitigation strategies for each. A polymorphic worm is where the body of the worm is encrypted and the decryptor code is mutated before it infects the next system. To detect polymorphic worms, we use an emulator, and the code will decrypt itself to detect the signature. A metamorphic worm is a worm where it mutates the body of the code before it infects the system. Can be detected by Hidden Markov Model Technique. Flash worm is designed to infect entire Internet almost instantly. To detect the flash worm, use Master IDS which it can slow down the flash worm because it's temporarily blocking off most of the nodes. Christina Viernes Kui Cheung

-- Solution for Practice Final

Originally Posted By: nealk

Neal Kemp
Chris Cook
Aida Khosroshahi

How does a Kerberized Login work?

[*]Alice's PC knows K_A because it is derived from her password... K_A=h(password)
[*]KDC knows K_A, thus can authenticate Alice
[*]Only KDC knows K_KDC, thus only KDC can decrypt TGT. TGT is used for passwordless reauthentication
[*]Alice forgets K_A after getting S_A (session key) and TGT
[*]Trudy doesn't know K_A or K_KDC; she cannot get S_A from any transaction

'''Originally Posted By: nealk''' Neal Kemp Chris Cook Aida Khosroshahi How does a Kerberized Login work? [*]Alice's PC knows K_A because it is derived from her password... K_A=h(password) [*]KDC knows K_A, thus can authenticate Alice [*]Only KDC knows K_KDC, thus only KDC can decrypt TGT. TGT is used for passwordless reauthentication [*]Alice forgets K_A after getting S_A (session key) and TGT [*]Trudy doesn't know K_A or K_KDC; she cannot get S_A from any transaction

-- Solution for Practice Final

Originally Posted By: askyous

Team members: Yousef, Danny

7. What is a software (a) error, (b) fault, (c) failure, (d) flaw?

error - programming fault

fault - an incorrect internal state

failure - program behaves incorrectly (external observable)

flaw - term to describe all of the above

'''Originally Posted By: askyous''' Team members: Yousef, Danny 7. What is a software (a) error, (b) fault, (c) failure, (d) flaw? error - programming fault fault - an incorrect internal state failure - program behaves incorrectly (external observable) flaw - term to describe all of the above

-- Solution for Practice Final

Originally Posted By: susandi

3. group member: Su Sandi, Sreenidhi
SSL sessions
It is an initializing protocol for securely authenticating web server to the client.
It is a negotiated cryptography parameter.
It is expensive since it involves public key operationssession1.jpg
SSL connections
It is designed for use with HTTP.
HTTP often opens multiple simultaneous connections.
It involves no public key operations (relies on known S)
It has an efficient protocol for opening new connections given an existing session.conn1.jpg

'''Originally Posted By: susandi''' 3. group member: Su Sandi, Sreenidhi SSL sessions It is an initializing protocol for securely authenticating web server to the client. It is a negotiated cryptography parameter. It is expensive since it involves public key operationssession1.jpg SSL connections It is designed for use with HTTP. HTTP often opens multiple simultaneous connections. It involves no public key operations (relies on known S) It has an efficient protocol for opening new connections given an existing session.conn1.jpg

-- Solution for Practice Final

Originally Posted By: Chol

Chol Gurung

Problem 9. Give an example of an incomplete mediation attack against a website.

Solution: Input validation is an example of incomplete mediation attack against a website.
Suppose the input is only validated on client. For example, consider the following URL:

http://www.things.com/orders/final&cust ... shipping=5
&total=205

On the server, this URL interprets to mean that the customer with ID number 112 has ordered 20 of the
item number 55 at a cost of $10 each, with $5 shipping charge with the total cost of $205.

Since the input is checked on client, the server does not check it again.
Now, Trudy can send the following URL to the server:

http://www.things.com/orders/final&cust ... shipping=5
&total=25

If the server does not validate the input, Trudy can receive the same order for bargain price of $25 instead of
real price of $205.

'''Originally Posted By: Chol''' Chol Gurung Problem 9. Give an example of an incomplete mediation attack against a website. Solution: Input validation is an example of incomplete mediation attack against a website. Suppose the input is only validated on client. For example, consider the following URL: http://www.things.com/orders/final&cust ... shipping=5 &total=205 On the server, this URL interprets to mean that the customer with ID number 112 has ordered 20 of the item number 55 at a cost of $10 each, with $5 shipping charge with the total cost of $205. Since the input is checked on client, the server does not check it again. Now, Trudy can send the following URL to the server: http://www.things.com/orders/final&cust ... shipping=5 &total=25 If the server does not validate the input, Trudy can receive the same order for bargain price of $25 instead of real price of $205.

-- Solution for Practice Final

Originally Posted By: andy

Andy Quach
Kurt Anderson

6.Explain how Alice and Bob can obtain a session for communication using Kerberos.

Alice enters her password to her computer. Her computer will derive K_a where K_a = h(Alice’s password), and then uses K_a to get TGT for Alice from KDC. Alice’s computer presents its TGT to the KDC, along with an authenticator. The authenticator is an encrypted timestamp that serves to avoid a replay. After the KDC verifies Alice’s authenticator, it responds with a “ticket to Bob”. Alice’s computer then uses this ticket to Bob to securely communicate directly with Bob’s computer.

REQUEST = (TGT, Authenticator)
Authenticator = E(timestamep, S_A)
TGT=E(Alice,S_A,K_KDC)
REPLY = E(“Bob”, K_ab, ticket to Bob, S_A)
Ticket to Bob = E (Alice, K_ab, K_b)

'''Originally Posted By: andy''' Andy Quach Kurt Anderson 6.Explain how Alice and Bob can obtain a session for communication using Kerberos. Alice enters her password to her computer. Her computer will derive K_a where K_a = h(Alice’s password), and then uses K_a to get TGT for Alice from KDC. Alice’s computer presents its TGT to the KDC, along with an authenticator. The authenticator is an encrypted timestamp that serves to avoid a replay. After the KDC verifies Alice’s authenticator, it responds with a “ticket to Bob”. Alice’s computer then uses this ticket to Bob to securely communicate directly with Bob’s computer. REQUEST = (TGT, Authenticator) Authenticator = E(timestamep, S_A) TGT=E(Alice,S_A,K_KDC) REPLY = E(“Bob”, K_ab, ticket to Bob, S_A) Ticket to Bob = E (Alice, K_ab, K_b)

-- Solution for Practice Final

Originally Posted By: kywong

Group: Kyle Wong, Vlad Iacob
1.
Perfect forward secrecy requires Alice and Bob to use Session keys Ks to encrypt instead of some static key K. Alice and Bob both forget Ks after they finish using it. The purpose of this is so that if Trudy figures out Ks, she cannot go back and decrypt all past cipher texts because each conversation used a different key.

One way to ensure PFS is to use Ephemeral Diffie-Hellman. The picture below explains the key exchange to determine Ks.

Ks = g^ab mod p. Once Ks is determined, Alice forgets a and Bob forgets b. This ensures that neither of them can later recover Ks. After Ks is finished being used, it is discarded and cannot be remembered.

'''Originally Posted By: kywong''' Group: Kyle Wong, Vlad Iacob 1. Perfect forward secrecy requires Alice and Bob to use Session keys Ks to encrypt instead of some static key K. Alice and Bob both forget Ks after they finish using it. The purpose of this is so that if Trudy figures out Ks, she cannot go back and decrypt all past cipher texts because each conversation used a different key. One way to ensure PFS is to use Ephemeral Diffie-Hellman. The picture below explains the key exchange to determine Ks. Ks = g^ab mod p. Once Ks is determined, Alice forgets a and Bob forgets b. This ensures that neither of them can later recover Ks. After Ks is finished being used, it is discarded and cannot be remembered.