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

Error reporting mechanism (icmp), ERROR REPORTING MECHANISM (ICMP) INT...

ERROR REPORTING MECHANISM (ICMP) INTRODUCTION:  IP gives best-effort delivery. Delivery causes can be ignored; datagrams may be 'dropped on the ground'. Internet Control Me

Network management, Ask question #MinimAn NMS is connected to a remote netw...

Ask question #MinimAn NMS is connected to a remote network by a 64 Kb/s link. The network elements in the remote network generate 50 faults/second. Of these, 5% are critical and th

Fragmentation format, FRAGMENTATION Fragmentation information is kept...

FRAGMENTATION Fragmentation information is kept in different extension header.  Every fragment has base header and fragmentation header. Whole datagram including original hea

Explain briefly the role of the physical layer, a) Calculate the CRC for th...

a) Calculate the CRC for the frame below: Frame: 1101011011 Generator: 10011 Message after appending 4 zero bits: 11010110110000 b) OSI refers to a system in which any

Deploying host-based idss, Deploying Host-Based IDSs -Proper implementat...

Deploying Host-Based IDSs -Proper implementation of HIDSs can be painstaking and time-consuming task .The process of deployment begins with implementing most critical systems fi

Area subdivision, the advantages and disadvantages of area subdivision and ...

the advantages and disadvantages of area subdivision and where it is applicable

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

Network security, Network security has become much more complex than ever b...

Network security has become much more complex than ever before. New types and sources of network security threats, always-on high-speed Internet connections, wireless networking, a

Explain the basic network topologies, Question: (i) ‘Implementation' is...

Question: (i) ‘Implementation' is a critical stage of the Systems Development Life Cycle. Show the four approaches which are commonly used to implement information systems in

Difference between synchronous tdm and statistical tdm, Question (a) A CRC...

Question (a) A CRC is constructed to generate a 4-bit FCS for an 11-bit message. The divisor polynomial is X 4 + X 3 + 1 (i) Encode the data bit sequence 00111011001 using po

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