C235: Johnny is Considering using the backup plan Shown in Table 1a to Backup Important data on a Server for the Month of August: IT Security Assignment, RP, Singapore

Question 1

Johnny is considering using the backup plan shown in Table 1a to backup important data on a server for the month of August. The backup is scheduled at 7.30 pm from Monday to Friday. There is no backup on Saturday and Sunday. The backup type and backup tape used are given in Table 1a.

Table 1a: Backup Plan A

a. Describe a problem if Johnny uses a rotation scheme where Tape 1, Tape 2,…, Tape 5 are re-used very every week. Explain your answer

b. Explain what should be done if the Grandfather-Father-Son (GFS) rotation is used. Your explanation should include the number of tapes required and how long should the tapes be preserved.

c. How many tapes are required to do a full restore of the server’s data if the server’s data is corrupted on the following days:

• 8 August at 6.00 pm
• 10 August 7.00 pm
• 16 August at 7.15 pm

Explain your answer and your explanation should include the sequence of the tapes required for the data restoration for each of the three days.

Question 2

Johnny is also considering using RAID 0, RAID 5, or RAID 6 for their server.

a. For the choice of RAID configuration, Johnny has the budget to use up to 6 disks of 1000 GB each and he also wants to achieve an amount of usable disk storage of 4,000GB. Which is the best RAID configuration he should use? Explain your answer.

b. To save cost, should Johnny choose the RAID configuration that requires the least number of disks to achieve the amount of usable disk storage of 4,000GB? Explain your answer.

Question 3

Hash values of the following files (File W, File X, File Y and File Z) are recorded from Sunday till Friday using a special type of hash algorithm.

Three backup types are considered to backup File W, File X, File Y, and File Z that reside in a system. A different backup tape is used each day, labelled Tape 1, 2, …, 6. For each day, backup is scheduled at 9 pm and will complete by 10 pm.

a. Which backup type(s) is/are used if Tape 4 at 10.30 pm contains File Z? Explain your answer.

b. Which backup type(s) is/are used if Tape 5 at 10.30 pm contains File X, File Y, File Z? Explain your answer

c. For the backup type identified in b), which backup tape(s) should be used to restore the file(s) if the system is corrupted on Friday at 11.30 pm?

d. For backup Type 2, which file(s) is/are in Tape 3 on Tuesday at 11.45 pm? Explain your answer.

Question 4

Roland and 6 other team members are working on a confidential project. On average, each one of them would send information to the rest of the team individually 5 times a day. They would like to adopt one of the following 3 cryptosystems for a trial to protect the information they send to each other. The trial period is 2 days long.

Cryptosystem 1:

Symmetric cryptosystem with a unique key shared between each pair.

Cryptosystem 2:

Asymmetric cryptosystem with digital signature

Cryptosystem 3:

Hybrid cryptosystem without digital signature (A new session key would be generated for each communication)

Which cryptosystem would require the

a. most number of keys

b. the least number of keys

Show your calculations.

Question 5

The plaintext is encrypted using Cipher 1 to produce a ciphertext which is then encrypted using Cipher 2 to produce another ciphertext. The different combinations of Cipher 1 and Cipher 2, and ciphertext produced (Ciphertext I, Ciphertext II,  …, or Ciphertext VI) are given in the table below:

a. Which ciphertext(s) can be decrypted by frequency analysis technique? Explain your answer.

b. Can you determine the highest frequency letter of the ciphertexts? For those that you can determine, state the highest frequency letter. Explain your answer.

Question 6

Password A is either 6,7 or 9 characters long and is formed from the following characters:

Qq C C D k l m a b c d A B C D e i o u X Y Z

Password B is also either 6, 7 or 8 characters long and is formed from the following characters:

W w C d F f g H H L l m n P Q R r S T U V Z

Computer I and Computer II, are used to crack these passwords. The computer I used was Brute Force Attack. Computer II used Dictionary Attack with 100,000,000 English words dictionary. The computer I can check 1,000,000 passwords per second and Computer II can check 500,000 passwords per second.

a. If characters can be repeated for Password A, what is the total number of possible passwords for Password A? Show your work.

b. If characters cannot be repeated Password B, what is the total number of possible passwords for Password B?  Show your working

c. What is the highest maximum time needed to crack Password A using Computer II? Explain your answer.

d. Which computer is more likely to crack password B? Explain your answer.