# Cryptography and Network Security Pdf Notes – CNS Notes | Free Lecture Notes download

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Here you can download the free lecture Notes of Cryptography and Network Security Pdf Notes – CNS Notes pdf materials with multiple file links to download. The CNS Pdf Notes book starts with the topics covering Information Transferring, Interruption, Interception, Services and Mechanisms, Network Security Model, Security, History, Etc.

## Cryptography and Network Security Pdf Notes – CNS Notes file

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

#### Link – Unit 5 Notes

Complete  notes

Note :- These notes are according to the R09 Syllabus book of JNTU.In R13 and R15,8-units of R09 syllabus are combined into 5-units in R13 and R15 syllabus. If you have any doubts please refer to the JNTU Syllabus Book.

• Introduction
• Information Transferring
• Attack: Interruption,Interception,Modification,Fabrication
• Attacks, Services and Mechanisms,Important Features of Security.
• Network Security Model,Cryptography,Basic Concepts,Encryption and Decryption.
• Security,History,Classical Cryptographic Techniques.
• Key Management,Attacks,Possible Attacks.Steganography,Caesar Cipher.
• Mathematical Model,Character Frequencies,Letter Frequency Analysis.
• Modular Arithmetic Cipher,
• Letter Frequency Analysis:Single Letter, Double Letter,Triple Letter.
• Playfair Cipher:Use filler letter to separate repeated letters,Encrypt two letters together.
• Analysis:Difficult to use frequency analysis,But vulnerable to known-plain text attack.

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Q1: What is Cryptography?

A1: Study of secret writing is called Cryptography. Crypto meaning secret and graphy means writing. The process is concerned with developing algorithms. It has the following charcteristis

• Conceal the context of some messages from all except the sender and recipient
• Verifying the correctness of a message to the recipient as in authentication of the message
• Form the basis of many possible technological solutions to computer and communication security problems

Q2: What is the difference between plaintext and ciphertext?

A2: Plaintext is the original intelligible message where as ciphertext is the transformed message of intelligible message by transposition and/or substitution

Q3: What are the two different securities?

A3: There are two fundamentally different securities

1. Unconditional security – Cipher cannot be broken even if there is a lot of power available
2. Computational security – The cipher cannot be broken when the computing resources provided is limited

Q4: What are the cryptography attacks?

A4: Basically there are two types of attacks:

1. Passive Attacks – These attacks are in the form of monitoring, transmission or eavesdropping on. Obtaining the transmitted information is the goal
of the opponent Passive attacks are of two types: One, release of message contents: A telephone conversation, an e-mail message and a transferred file
may contain sensitive or confidential information. Second, traffic analysis: If we had encryption protection in place, an opponent might still be able to
observe the pattern of the message. The opponent could determine the identity and location communication hosts. He/she could observe the frequency and length of messages being exchanged. This information might be useful in guessing the nature of communication.
Since passive attacks do not involve any alteration of data, they are very difficult to detect. However, it is very much possible to prevent the success of these attacks.
2. Active attacks: Active attacks involve some alteration of the data stream or the formation of a false stream. These attacks can be sub-classified in to four more categories:
1. Masquerade – One entity pretends to be as a different entity.
2. Replay – Production of an unauthorised effect by passive capture of a data unit and its subsequent transmission.
3. Modification of messages – Some part of the message is altered or the messages are recorder or delayed which produces an unauthorized effect.
4. Denial of service – Inhibits the normal use or management of communication facilities. Another form is the disruption of an entire network. It could be either by disabling the network or overloading it with messages. It degrades the performance.
It is very much difficult to prevent active attacks. Because to do so, it would require physical protection of all communication facilities and paths at all times. Instead, the goal is to detect them immediately and recover the information from any disruption or delays caused by them.

Q5: What are the core principles of modern-day cryptography?

A5: Four core principles of modern-day cryptography are, Data Confidentiality, Data Integrity, Authentication and Non-repudiation.

1. Confidentiality: This refers to certain rules and guidelines usually executed under confidentiality agreements which ensure that the information is restricted to certain people or places.
2. Data integrity refers to maintaining and making sure that the data stays accurate and consistent over its entire life cycle.
3. Authentication is the process of making sure that the piece of data being claimed by the user belongs to it.
4. Non-repudiation refers to ability to make sure a party or a person associated with a contract cannot deny the authenticity of their own signature over their document.