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Cyber Security Notes, Lecture notes of Computer Science

Dr. A.P.J. Abdul Kalam University Computer Science

Covers Some topics of Cyber security

Typology: Lecture notes

2019/2020

Uploaded on 12/17/2020

aalok-srivastava 🇮🇳

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Computer System Architecture Dept. of Info. Of Computer.Chap. 12 Memory Organization

12-1

Cryptography & Network Security

Cryptography : A word in Greek origin means “ Secret writing”

Cryptography (Basic definition)

◆It is the science and art of transforming messages to make them

secure and immune to attacks.

Different types of Cryptography

◆Symmetric Key Cryptography : Same key will be used for encryption

& decryption.

◆Asymmetric Key Cryptography: One key will be used for encryption

and another key will be used for decryption.

Partial preview of the text

Download Cyber Security Notes and more Lecture notes Computer Science in PDF only on Docsity!

Cryptography & Network Security

Cryptography : A word in Greek origin means “ Secret writing”

Cryptography (Basic definition)

◆ It is the science and art of transforming messages to make them

secure and immune to attacks.

Different types of Cryptography

◆ Symmetric Key Cryptography : Same key will be used for encryption

& decryption.

◆ Asymmetric Key Cryptography: One key will be used for encryption

and another key will be used for decryption.

Goals of Network Security

Privacy or Confidentiality:

◆ It is used to protect data from disclosure attack.

Authentication:

◆ It is used to provide authentication of the party at either end of the

line.

Integrity:

◆ It is used to protect data from modification, insertion, deletion etc.

Non-Repudiation:

◆ This service protects against repudiation either by sender or the

receiver.

Public-Key/Asymmetric Key cryptosystem

Main ingredients of Public Key Cryptosystem:

◆ Plaintext

◆ Encryption algorithm

◆ Public and private key

◆ Ciphertext

◆ Decryption algorithm

Asymmetric Key cryptosystem

General idea of asymmetric-key cryptosystem

12 - 7 1 3 . 7

Digital Signature

Digital signature process

Adding key to the digital signature process

A digital signature needs a public-key system.

The signer signs with her private key; the verifier

verifies with the signer’s public key.

Note

Digital Signature

Malicious Programs

Trapdoors

Secret entry point into a program.

Allows those who know access bypassing usual security procedures.

Have been commonly used by developers.

Threat when left in production programs, allowing exploited by attackers

Requires good s/w development & update.

Trojan Horse

Program with hidden side-effects.

Which is usually superficially attractive

◆ eg game, ZIP software etc.

When run performs some additional tasks

◆ allows attacker to indirectly gain access they do not have directly

Often used to propagate a virus/worm or install a backdoor or to destroy

data.

Zombie

Program which secretly takes over another networked computer then

uses it to indirectly launch attacks.

Often used to launch distributed denial of service (DDoS) attacks.

Types of Viruses

Parasitic virus: The traditional and still most common form of virus. A parasitic virus attaches itself to executable files and replicates, when the infected program is executed, by finding other executable files to infect. Memory-resident virus: Lodges in main memory as part of a resident system program. From that point on, the virus infects every program that executes. Boot sector virus: Infects a master boot record or boot record and spreads when a system is booted from the disk containing the virus.

Types of Viruses

Stealth virus: A form of virus explicitly designed to hide itself from

detection by antivirus software. For ex: Using compression to hide

increased file size due to infection.

Polymorphic virus: A virus that mutates with every infection, making

detection by the "signature" of the virus impossible. For ex: To insert

superfluous instructions or change the order of independent instructions.

Macro-virus

Macro code attached to some data file

Interpreted by program using file

◆ ex: Word/Excel macros

◆ ex: Using auto command & command macros

Code is platform independent

A macro virus is platform independent. Virtually all of the macro viruses

infect Microsoft Word documents. Any hardware platform and operating

system that supports Word can be infected.

Worms

A worm is a program that can replicate itself and send copies from computer to computer across network connections. Upon arrival, the worm may be activated to replicate and propagate. Also, the worm usually performs some unwanted function. An e-mail virus has some of the characteristics of a worm, however, we can still classify it as a virus because it requires a human to move it forward. To replicate itself, a network worm uses some sort of network vehicle. For ex. : Electronic mail facility, Remote login capability etc. The new copy of the worm program is then run on the remote system continues to spread in the same fashion. Ex: Stuxnet, used to disturb Iranian nuclear program.

Cyber Security Notes, Lecture notes of Computer Science

Related documents

Partial preview of the text

Download Cyber Security Notes and more Lecture notes Computer Science in PDF only on Docsity!

Cryptography & Network Security

Cryptography : A word in Greek origin means “ Secret writing”

Cryptography (Basic definition)

◆ It is the science and art of transforming messages to make them

secure and immune to attacks.

Different types of Cryptography

◆ Symmetric Key Cryptography : Same key will be used for encryption

& decryption.

◆ Asymmetric Key Cryptography: One key will be used for encryption

and another key will be used for decryption.

Goals of Network Security

Privacy or Confidentiality:

◆ It is used to protect data from disclosure attack.

Authentication:

◆ It is used to provide authentication of the party at either end of the

line.

Integrity:

◆ It is used to protect data from modification, insertion, deletion etc.

Non-Repudiation:

◆ This service protects against repudiation either by sender or the

receiver.

Public-Key/Asymmetric Key cryptosystem

Main ingredients of Public Key Cryptosystem:

◆ Plaintext

◆ Encryption algorithm

◆ Public and private key

◆ Ciphertext

◆ Decryption algorithm

Asymmetric Key cryptosystem

General idea of asymmetric-key cryptosystem

Digital Signature

Digital signature process

Adding key to the digital signature process

A digital signature needs a public-key system.

The signer signs with her private key; the verifier

verifies with the signer’s public key.

Note

Digital Signature

Malicious Programs

Trapdoors

Secret entry point into a program.

Allows those who know access bypassing usual security procedures.

Have been commonly used by developers.

Threat when left in production programs, allowing exploited by attackers

Requires good s/w development & update.

Trojan Horse

Program with hidden side-effects.

Which is usually superficially attractive

◆ eg game, ZIP software etc.

When run performs some additional tasks

◆ allows attacker to indirectly gain access they do not have directly

Often used to propagate a virus/worm or install a backdoor or to destroy

data.

Zombie

Program which secretly takes over another networked computer then

uses it to indirectly launch attacks.

Often used to launch distributed denial of service (DDoS) attacks.

Types of Viruses

Types of Viruses

Stealth virus: A form of virus explicitly designed to hide itself from

detection by antivirus software. For ex: Using compression to hide

increased file size due to infection.

Polymorphic virus: A virus that mutates with every infection, making

detection by the "signature" of the virus impossible. For ex: To insert

superfluous instructions or change the order of independent instructions.

Macro-virus

Macro code attached to some data file

Interpreted by program using file

◆ ex: Word/Excel macros

◆ ex: Using auto command & command macros

Code is platform independent

A macro virus is platform independent. Virtually all of the macro viruses

infect Microsoft Word documents. Any hardware platform and operating

system that supports Word can be infected.

Worms