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
Question: (a) Explain and illustrate with a drawing the three-layer feedforward multilayer perceptron neural network. (b) Summarize the standard backpropagation algorithm in

An injunction to 'think ethically' about a situation is not helpful. Perhaps if one has a background in moral philosophy this would work, but usually both students and IT professio

a) Explain the contents of the Cost Assessment. b) Various Documents are needed for Configuration Management. State three of them, and describe their importance. c) Given tha

LOCAL TALK Apple discovered the LAN technology that uses bus topology. Its interface is added with all Macintosh computers. It has very low speed i.e. 230.4Kbps. Also it is ch

There are various benefits related with providing the security. They are given below,  (i)  Confidentiality/ Privacy (ii)  Integrity  (iii) Availability (iv)Authenticatio

Question 1: (a) (i) Radio waves are subject to several propagation problems. Name any three of them. (ii) A Wi-Fi receiver requires a signal power of 50mW to operate correc

Question 1 (a) Explain briefly the following terms as used in network security: (i) Denial of service (DoS) attack (ii) Birthday attack (iii) DeMilitarized Zone

Question 1: Why do we need a Law of Contract? a Explanation Reasons to have a law of contract b Explain the close procurement project process - Explanation (causes,

TRANSMISSION ERRORS:  Transmission exceptions may happen due to different causes for example power surges or interference may delete data during transmission. In result of wh

why is it that sometime we put password in our account to login or signup and it would not work?