1. Suppose you have a secure system with three subjects and three objects,with levels as listed below.

Here H dominates L. You wish to implement a Bell and LaPadula model of security for this system. Fill in the access rights (R and/or W) permitted by the model for each subject/object pair in the access matrix below:

(1) Subject: (H, {A}), Object: (L, {A,B})
- Can the subject read the object? Justify your answer

(2) Subject: (H, {A,B}), Object: (L, {A })

- Can the subject read the object? Justify your answer

(3) Subject: (L, {A,B}), Object: (H, {A })
- Can the subject read the object? Justify your answer

(4) Subject: (L, {A,B}), Object: (H, {A })
- Can the subject read the object? Justify your answer

(5) Subject: (H, {A,B,C}), Object: (H, {A,B })
- Can the subject read the object? Justify your answer

(6) Subject: (L, {A,B}), Object: (L, {C})
- Can the subject read the object? Justify your answer

2. Suppose a department has determined that some users have gained unauthorized access to the computing system. Managers fear the intruders might intercept or even modify sensitive data on the system. Cost to reconstruct correct data is expected to be $1,000,000 with 1% likelihood per year.

One approach to addressing this problem is to install a more secure data access control problem. The cost of access control software is $100,000 with 20% effectiveness.

(1) What is the expected annual total costs?

(2) What is the saving?

(3) Answer if it is worthwhile to invest on the access control software. Justify your answer.

3. Suppose the following:

- James' public key = Kj, James' private key = Kj-1
- Randy's public key = Kr, Randy's private key = Kr-1
- Each person's public key is known to others; Each one's private key is only known to the owner

a) Explain how Randy can send a plaintext P to James secretly

b) Explain how James can verify if a plaintext P is sent from Randy

c) Explain how Randy can verify if a plaintext P is sent from James and at the same time P is sent secretly from James to Randy.

4. IONA Corporation has the following class C Internet License: 193.1.1.0. IONA Corp. would like to allow for exactly 32 sub-networks using subnetting.

(193.45.1.0 -> 11110001.00000001.00000001.00000000)
a) How should Iona Corp. divide up the bits in their Class C license to allow for this?

b) How many devices on each subnet would this allow? Justify your answer

c) What would their subnet mask be? Justify your answer

d) What would be the IP address (Subnet ID) of the first useable subnet id?

e) What would be the IP address of the first useable host id on the first usable subnet id?

f) What would be the IP address of the last useable host id on the first useable subnet id?

g) What would be the broadcast address of the first useable subnet id?

5. Summarize one of the following topics within one page:

- Subnet and Subnet mask
- ARP Protocol
- TCP Protocol