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# 10. (5 points) Double transposition ciphers were very secure

10. (5 points) Double transposition ciphers were very secure hand encryption methods used during World War II by both the Allies and the Axis and is described in some detail here:

http://www.pbs.org/wgbh/nova/decoding/doubtrans.html

The following message was encrypted using a double transposition cipher:

PRINS NOLOO EEPIL RGVST OPAEA SETVT LSVIL ECSSO BITUP EASTH SLAHB OEEIP I

The key for the first transposition is DURABLE; the key for the second transposition is FIREWANDS. Decrypt the message (be sure to show your work)

11. (5 points) The message below is encrypted using an affine cipher (information about affine ciphers can be found here: http://en.wikipedia.org/wiki/Affine_cipher ) with a = 3 and b = 8. Decrypt the message.

SUHHC ODHGKNSIK IVR DIBBC VUW CUIH

An affine cipher is a monoalphabetic substitution cipher where the ciphertext is encrypted from the plaintext by the formula:

C(P) = (a x P + b) mod 26

7. (10 points) In your corporate environment the company depends heavily on the customer database for sales lead information and for revenue tracking. The database is hosted on a server in the corporate data center which is offsite. One day the power connection from the utility company to the data center is lost…however, the data center staff do not realize this as the data center immediately switched over to their backup diesel generator. Unfortunately the data center staff, not being aware that they were on backup power, never check the fuel level of the generator and it runs out of fuel. All of the systems in the data center go down. The outage lasts for 12 hours.
Outage duration 12 hours
Annual corporate revenue based on sales \$12,000,000
Asset Value of corporate data center \$500,000
Asset value of database server 10% of datacenter
Annual Rate of Occurrence 1 in 100

Determine the following information:

a. Calculate the Single Loss Expectancy (SLE) (3 points)
b. Calculate the Annual Loss Expectancy (ALE) (3 points)
c. The cost of controls is the purchase of a UPS system for \$1000. Determine the ALE after the controls (assume the ARO goes to 1 in 500) (2 points)
d. Calculate the risk leverage (2 points)

How soon do you need this? I have the first cypher done. (I like the quote, BTW)

The last question is going to take me some time to research.

The formula I have needs a value for "exposure factor." Is that computed from the information given? If so, do you have a better formula that I can use?

Customer: replied 4 years ago.

How can I see the answers? This is due by tomorrow midnight.

I will give the answers when I have them all to give you. Do you have the formula I asked for?
Customer: replied 4 years ago.

Is this ok?

ALE Examples

ARO: Annual Rate of Occurrence – the number of times in a given year that an event is expected to

occur. This can be expressed as a fraction (such as 1 in 15, 1 in 200, 1 in X, etc.) meaning that the

event is expected to occur at least once (1) in some number of years (X).

ALE: Annual Loss Exposure (aka risk exposure) – the expected annual loss due to an event. This is

typically expressed as a dollar amount.

Examples:

Problem #1:

You work for a company whose offices are flooded. All of the servers in the corporate data center

on site are ruined. The total cost of all the systems was \$500,000. The offices happened to be in a

100-year flood plain (the ARO for a massive flood in a given year was 1 in 100). Calculate the ALE

for this event.

Solution #1:

In this case the ARO is already given: 1 in 100 = .01

The cost of the systems is \$500,000.

So, the ALE is the cost of the systems multiplied by the ARO or:

\$500,000 x .01 = \$5000

Now, this is NOT the cost of the loss. This is the annual risk exposure that a massive flood would

take out the systems. The cost of the loss, if a 100-year flood occurs is \$500,000. This is just a way

to give IT and security managers a way to figure out whether they need to install a control that

would mitigate this problem.

Problem #2:

Your company pays an annual maintenance fee of \$1000 to an anti-virus company, MyAV.com, to

stay current on the anti-virus software. One day, an employee receives an e-mail with a new virus

attached and opens the e-mail. Every mailbox in the company directory is infected. It will take

the IT staff 3 days to clean all of the affected mailboxes at a cost of approximately \$10,000. The

chance of this happening, according to MyAV.com’s account manager, was 1 in 20. In addition,

the cost of loss of sales opportunity amounts to an additional \$25,000. Calculate the ALE.

Solution #2:

In this case the total loss is the loss of sales opportunities as well as the cost of the cleanup:

\$10,000 + \$25,000 = \$35,000.

MyAV.com claims that the ARO was 1 in 1000 or .05

Therefore the ALE is: \$35,000 x .05 = \$1,750

Problem #3:

The account manager for another anti-virus company, YourAV.com, contacts you after he hears

about your virus infection. He claims that his product, YourAV, would perform better than the

competitor, MyAV, and that such an event with his product would only have a 1 in 200 chance of

occurring. He offers you a competitive “upgrade” to his product for \$500.00. Calculate the ALE

and the risk leverage.

Solution #3:

The loss in this case would still be \$35,000. But now, the ARO is .005. So, the ALE is:

\$35,000 x .005 = \$175.00

The risk leverage is:

[ (\$1,750) – (\$175) ] / \$500 = 3.15 (a relatively low number and so the solution is worthwhile

Thank you for this. I will study it and will get it done. What is the deadline?
Customer: replied 4 years ago.

Can I get it by tomorrow morning! It is due by tomorrow night( final deadline).

No problems. Your post said high urgency, so I was afraid it was due very soon.

Customer: replied 4 years ago.

Ok and thanks! Just want to put it together with other questions when I receive them. How is it going by the way?

I have double and triple checked the numbers. I am quite happy with them, but please check it again. I told you that I am not familiar to this topic.

Attachment: 2013-04-28_022441_riskleverage.xls

OH! Hold on. Cancel that. I need to fix them!

I suddenly remembered that the loss was 12 hours instead of 24.

Attachment: 2013-04-28_022709_riskleverage.xls

Customer: replied 4 years ago.

Ok, let me try wikisend.

Excel file

Are you able to get that file?
Customer: replied 4 years ago.

Yes, please convert it into a word document so that I can copy and paste in my home curate?which is a word document as well. Can you also ensure that the risk answer is demonstrated with steps and ac

Ummmm. Okay. I used Excel for the calculations, but I guess I can give it a shot. Give me a little.

You need to spend \$3 to view this post. Add Funds to your account and buy credits.
Customer: replied 4 years ago.

Thanks! I justed dowloaded it and will let you know. I also submitted new questions and can you look them? I will complette the survey as well!

I did look at them, but I cannot do them. I do not know the topic.
Customer: replied 4 years ago.

Ok, they are information assuarance and networking! How do you feel for the previous answers? Do the affine has to align( rows)?

The affine is just in rows to show how it works. C (number 2) goes to O (number 2*3+8=14) whether it is in rows or not.