tailieunhanh - Lecture Network security: Chapter 11 - Dr. Munam Ali Shah

The topic discussed in this chapter are cryptography as a network security tool. In this chapter we will talk about 3-Dimesions of cryptography; cryptanalysis and brute force attacks; classical ciphers: substitution cipher, transposition cipher. | Network Security Lecture 11 Presented by: Dr. Munam Ali Shah Part 2 (b) Cryptography as a Network Security Tool Summary of the previous lecture We had overviewed what cryptography is and how can we use this tool to incorporate security We discussed different terminologies such as Alice, Bob, Eve, Key, cryptanalysis, steganography etc. We also reviewed how encryption and decryption using keys work. 4 types of cryptanalysis Summary of the previous lecture Outlines of today’s lecture We will talk about : 3-Dimesions of Cryptography Cryptanalysis and Brute Force Attacks Classical Ciphers Substitution Cipher Transposition Cipher Objectives You would be able to understand and explain basic cryptography techniques Understand and practice the basics phenomenon to perform cryptanalysis Cryptography Cryptographic systems are characterized along three independent dimensions: The type of operations used for transforming plaintext to ciphertext. The number of keys used. The way in which the . | Network Security Lecture 11 Presented by: Dr. Munam Ali Shah Part 2 (b) Cryptography as a Network Security Tool Summary of the previous lecture We had overviewed what cryptography is and how can we use this tool to incorporate security We discussed different terminologies such as Alice, Bob, Eve, Key, cryptanalysis, steganography etc. We also reviewed how encryption and decryption using keys work. 4 types of cryptanalysis Summary of the previous lecture Outlines of today’s lecture We will talk about : 3-Dimesions of Cryptography Cryptanalysis and Brute Force Attacks Classical Ciphers Substitution Cipher Transposition Cipher Objectives You would be able to understand and explain basic cryptography techniques Understand and practice the basics phenomenon to perform cryptanalysis Cryptography Cryptographic systems are characterized along three independent dimensions: The type of operations used for transforming plaintext to ciphertext. The number of keys used. The way in which the plaintext is processed. 3- Dimensions of cryptography 1- The type of operations used for transforming plaintext to ciphertext. All encryption algorithms are based on two general principles: substitution, in which each element in the plaintext (bit, letter, group of bits or letters) is mapped into another element, and transposition, in which elements in the plaintext are rearranged. The fundamental requirement is that no information be lost (., that all operations are reversible). Most systems, referred to as product systems, involve multiple stages of substitutions and transpositions. 3- Dimensions of cryptography 2- The number of keys used. If both sender and receiver use the same key, the system is referred to as symmetric, single-key, secret-key, or conventional encryption. If the sender and receiver use different keys, the system is referred to as asymmetric, two-key, or public-key encryption. 3- Dimensions of cryptography 3- The way in which the plaintext is processed. A block cipher