Explain transposition ciphers and substitution cipher, Computer Network Security

What do you understand by cryptanalysis? Discuss about the transposition ciphers substitution cipher, and onetime pads.

The messages which are intended to transmit secretly and securely with full protection are subjected to the process of encryption and decryption in order to provide the desired security. The original message which is to be encrypted is called plain text. This plain text is transformed by a function with the encryption key (K) as parameter. The plain text after the transformation that is the output of the encryption process is called as cipher text. And this cipher text or the encrypted message with key is actually transmitted.

Although an intruder listens to this message/cipher text by catching the communication channel still he cannot decrypt the cipher text because he doesn't know key. Even though he doesn't know the key still he is able to break that cipher text at times and that art of breaking ciphers is known as cryptanalysis.

The art of devising and breaking ciphers is collectively called as cryptology. The encryption methods/techniques are, divided into the following two categories,

1. Substitution Ciphers

2. Transposition Ciphers.

1. Substitution Ciphers:

In this cipher, each letter or the group of letters is replaced by another group of letters. Good instance of substitution cipher is Caesar cipher. In this cipher, a becomes D, and b becomes E and so on and the Z becomes C.

An Example is written below:

An Attack becomes DWWDFN

This general system is called the mono alphabetic substitution.

In substitution ciphers, order of letters is similar to that of plain text but just disguises them.

2. Transposition Ciphers

In contrast to the substitution ciphers, transposition ciphers read the letters but do not disguise them. The key of this cipher is a word, having no repeated letters. An instance of a transposition cipher text is given below.

1627_cipher.png


The main purpose of the key is to number the columns. The plain text is in rows and cipher text is prepared by assembly letters in columns.

Onetime Pads is defined below:

There is a simple way of constructing an unbreakable cipher. The procedure is initiated with the choice of a random bit string as key. Converting plaintext into a bit string and computhexc1usjve OR operation for these two strings This method/technique is known as Onetime Pad.

Posted Date: 7/20/2012 6:10:35 AM | Location : United States







Related Discussions:- Explain transposition ciphers and substitution cipher, Assignment Help, Ask Question on Explain transposition ciphers and substitution cipher, Get Answer, Expert's Help, Explain transposition ciphers and substitution cipher Discussions

Write discussion on Explain transposition ciphers and substitution cipher
Your posts are moderated
Related Questions
Get a copy of Metasploitable at Make">http://sourceforge.net/projects/metasploitable/files/Metasploitable2/ Make sure to follow these directions very carefully. You will get po

CONCEPT OF PACKET : Network systems splits data in small junks or blocks known as packets, which they send individually. Why we required packets rather than bits? The answer to

How safe is the encryption of virtual private networks?

Identify Possible Controls For each threat and linked vulnerabilities which have residual risk, create primary list of control ideas. Residual risk is the risk which remains to

ADDRESS RESOLUTION AND PROTOCOL ADDRESSES Address resolution (ARP) is a network interface layer protocol. Protocol addresses are used in all upper layers. Address resolution s

Illustrate about TinySec Protocol TinySec is implemented on the link layer and addresses security requirements of the resource staffed nodes in the WSN based on the link layer

QUESTION (a) Which PKI (Public Key Infrastructure) model is typically favored by business organization? (b) Give one possible use of the "extensions" field of an X.509 certi

doing coursework in Network Security to present a possible solution to the problem at hand by creating a prototype of the new network security infrastructure. This new design shou

Question (a) Name 3 popular electronic mail access protocols? (b) i. What is DNS? ii. Briefly, describe what it does and how it works? iii. Why does DNS use a dist

Categories of Controls Controlling risk through mitigation, avoidance or transference is accomplished by implementing controls. There are 4 effective approaches to select the co