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
1.  We used the National Vulnerability Database. Select a recent vulnerability from that Database and analyse it from the following aspects: Criticality level Impact in

QUESTION: a) Explain four issues that are generally addressed in the Needs Analysis phase in the building-block approach to network design. b) Sketch a typical hybrid star-b

how to encryt the data in plaintext cipher

In the early days when there were some dozen computers machine on the network, it was done individually but now as we have looked that there are millions of computers on the intern

Problem: (a) What is the minimum length of a password that could be considered to be "strong" in the context of today's computing power? (b) The security of a PIN system,

QUESTION a) Consider the speed of propagation of an electrical signal is same to 2x10 8 m/s, evaluate the ratio of the propagation delay to the transmit time for the given typ

How can I get help for Linux automotion configuration (Network, virtualization, security and Firewal etc) with bash scrip. What is the charge for.

Problem (a) Distinguish between passive and active attacks. (b) Give two reasons why it is important to organise security awareness programs for users. (c) Describe how

ADDRESS RESOLUTION WITH CLOSED-FORM COMPUTATION For networks use reliable addressing, it is possible to select an address that creates closed-form address resolution possible.

Network-Based IDS (NIDS) A NIDS resides on computer or appliance connected to segment of an organization’s network and looks for signs of attacks. While examining packets, a NID