Find the possible deciphering transformations, Computer Network Security

Assignment Help:

Question:

(a) A string of ciphertext was enciphered using an a±ne transformation of single letters in a 28-letter alphabet consisting of A to Z, a blank and a?, where A to Z have numerical equivalents 0 to 25, blank=26, ?=27. A frequency analysis reveals that the the first, second and third most common letters of this ciphertext are B, ? and I, respectively. Suppose that the first and second most common letters in an English language text written in this 28-letter alphabet are ` '(blank) and E, respectively.

(i) Find the possible deciphering transformations.

(ii) Using the fact that T, is the third most common letter in the English language (of our 28 letters), find the right deciphering transformation.

(b) The ciphertext

¡GSTMTSI XJMUIGHRFKYMV

was generated using a 2£2 enciphering matrix with a 29¡letter alphabet, where A to Z have numerical equivalents 0 to 25, blank=26, !=27, and ¡ = 28. Given that the last five letters of the plaintext are A¡ONE, determine the complete plaintext.


Related Discussions:- Find the possible deciphering transformations

Explain the limitations of a firewall, Question: (a) Mention three lim...

Question: (a) Mention three limitations of a firewall. (b) Compare packet-filtering and proxy-base firewalls. Give advantages and drawbacks of both. (c) "Proxies eff

What is the use of digital certificate, Question: (a) What is the use ...

Question: (a) What is the use of digital certificate? (b) What is meant by a hierarchical trust model in a Public Key Infrastructure? How does the Pretty Good Privacy (PG

What is the main security vulnerability of ipv4, Question: (a) What is...

Question: (a) What is the main security vulnerability of IPv4? (b) Which protocol can be used for secure remote login? (c) Distinguish between the transport and tunnel

Provide a labelled drawing of a standard serial port, Question 1: (a) W...

Question 1: (a) With the help of a diagram show the basic structure of a computer system. (b) Explain as fully as you can each of the parts mentioned above. (c) What are

Explain the operation of the matchmaker middle agent, Question 1: (a) E...

Question 1: (a) Explain the operation of the "matchmaker" middle agent. (b) Describe why broker middle agents are more efficient in terms of the time taken for a service to

Major difference between a virus and a worm, Question: (a) State wheth...

Question: (a) State whether the following statements are TRUE or FALSE. Justify your answer. i. A good site security policy will require that users use computer generated p

Risk determination, Risk Determination For purpose of relative risk asse...

Risk Determination For purpose of relative risk assessment, risk equals probability of vulnerability occurrence TIMES value MINUS percentage risk already controlled PLUS an elem

Find the capacity of the wcdma, Question: (a) Describe the term interfe...

Question: (a) Describe the term interference in the space, time, frequency, and code domain. (b) Consider a 1 G - AMPS: 824-849 MHz (forward) ; 869-894 MHz (reverse). B

Negative cycle algorithm in minimum cost flows, QUESTION: (a) Show the...

QUESTION: (a) Show the Negative Cycle Algorithm in Minimum Cost Flows. (b) List the steps added in finding a Negative Cycle. (c) Apply Dijkstra's algorithm on the subs

Access control list, Scenario: A network with individual hosts (really, vir...

Scenario: A network with individual hosts (really, virtual machines) can run HTTP (web) servers that are available to the outside. (Here, available means the ability to read and wr

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd