Cipher methods-cryptography, Computer Network Security

Cipher Methods

There are 2 methods of encrypting plaintext:

• Bit stream method – every bit in the plaintext bit is transformed into a cipher bit one bit at a time.
• Block cipher method – the message is divided into blocks (for example sets of 8-, 16- or
32-bit blocks) and then each block of plaintext is transformed into an encrypted block of cipher bits by using an algorithm and a key.

Bit stream method which is uses algorithm functions like XOR, while block cipher method can use substitution, transposition, XOR, etc.

Substitution cipher

Substitution cipher substitutes one value for the other value. The following are the different types of substitution:
• Monoalphabetic substitution – It uses one alphabet to substitute. Simple method but powerful if combines with other operations.
• Polyalphabetic substitution – It is more advanced method which uses two or more alphabets.
• Vigenère cipher – It is an advanced type of cipher which uses simple polyalphabetic code that is made up of 26 distinct cipher alphabets.

Transposition cipher

Transposition cipher rearranges values within the block to create ciphertext.

Exclusive OR (XOR)

It is a function of Boolean algebra where the two bits are compared to each other
•     If the two bits are identical, result is 0
•     If the two bits not identical, result is 1

Vernam cipher

This is developed at AT&T that uses set of characters once per encryption process.

Book (or Running Key) cipher

This method uses text in book as key to decrypt a message where ciphertext contains codes which represents page, line and word numbers

Hash Functions

Hash functions are mathematical algorithms that generate message summary or digest to confirm message identity and confirm no content has changed. Hash algorithms are publicly known functions that create hash value. Use of keys is not needed, but message authentication code (MAC) may be attached to a message. This method is mostly used in password verification systems to confirm identity of user.

Posted Date: 10/8/2012 7:10:58 AM | Location : United States

Related Discussions:- Cipher methods-cryptography, Assignment Help, Ask Question on Cipher methods-cryptography, Get Answer, Expert's Help, Cipher methods-cryptography Discussions

Write discussion on Cipher methods-cryptography
Your posts are moderated
Related Questions
Problem: (a) What is a firewall and which are its most important tasks? (b) What is the difference between default deny and default permit? Which advantages and disadvanta

Implementing an effective online authentication scheme in practice faces many challenges. Systems with highly sensitive data often require multifactor authentication. But, requirin

Question 1 Explain any two types of security policies Question 2 What is security attack? Explain with examples Question 3 Explain different characteristics that i

(a) Cost allocation mechanisms are important when it comes to establishing other aspects of inter-firm compensations and how these are transferred to the users. There are two pri

What is one-time pad for encryption?  Describe how it offers both Confusion and Diffusion. Using the letter encoding discussed in class (along with one-time

Question: (a) Which of the following is not a goal of security: i) detection ii) prevention iii) recovery iv) prosecution (b) You are an honest student. One day you

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

Question : (a) "Pulse Code Modulation (PCM), as used in telephony, samples a signal at 8 kHz using 256 quantization levels". Outline how this scheme works with the help of ske

You are an IT Security administrator in a banking organization. Your organization hired an outside IT firm to do a proof of Concept for new equipment which is a computer based syst

QUESTION a) "Two of the key attributes of an enterprise network is that it have to be multi-platform and multisite." Decribe what you understand by this statement. b) A