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
Gateways They transfer packets among network machines that have different protocols (e.g. between a WAN and a LAN). They access a packet formatted for one protocol and change

Asymmetric Encryption Asymmetric encryption method makes use of two different but related keys and either key can be used to encrypt or decrypt the message. This method is freque

QUESTION: (a) Below is a capture of an Ethernet II frame which contains an IPv4 packet and a TCP segment. Give the source MAC address for the frame in hexadecimal; the sourc

Problem (a) Give two reasons for companies to implement security measures. (b) What is the regulatory expectation regarding i. healthcare information, ii. financial

(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

Question: Spreadsheet packages are widely used in Business. a) Explain why spreadsheets are so useful. b) Spreadsheet files are sometimes saved for use by other software

Threat Identification After identifying and performing a primary classification of an organization’s information assets, the analysis phase moves onto an examination of threats

QUESTION (a) (i) Describe Phishing attacks. (ii) Distinguish between Phishing and Spear Phishing attacks. (b) Describe two instances where an attacker sniffing on a netwo