Cryptography(1)

Information Assurance and Security

  • Focus on Cryptography & Network Security

Introduction

  • Importance of Cryptography

    • Data travels between computers, vulnerable outside protected environments

    • Risk of data modification and forgery by malicious actors

    • Cryptography reformats and protects data during transmission

    • Based on secret codes and advanced mathematics

Types of Security

  1. Computer Security

    • General tools and measures to protect data from hackers

  2. Network Security

    • Strategies to protect data during transfers over networks

  3. Internet Security

    • Measures to safeguard data across interconnected networks

  4. Differences

    • Computer Security: Protects data on a single device

    • Network Security: Protects data in transit

    • Internet Security: Broader protection over multiple networks

Security Attacks

  • Definition: Actions that compromise organizational data security

  • Three key aspects:

    1. Assess security needs systematically

    2. Mechanisms for prevention, detection, and recovery

    3. Services to enhance security and counter attacks

Cryptography

  • Definition: The art/science of transforming intelligible messages into unintelligible formats and back

  • Key Concepts:

    • Plaintext: Original message

    • Ciphertext: Transformed message

    • Cipher: Algorithm for transformation (transposition/substitution)

    • Key: Critical piece of information, known only to sender & receiver

    • Enciphering: Converting plaintext to ciphertext

    • Deciphering: Converting ciphertext back to plaintext

    • Cryptanalysis: Breaking codes without key knowledge

    • Cryptology: Study of both cryptography and cryptanalysis

    • Code: Similar to cipher but involves a codebook

Encryption and Decryption

  • Basic Process:

    • Transformation of plaintext into ciphertext and vice versa

    • Visualization:

      • Plaintext ➔ Encryption ➔ Ciphertext

      • Ciphertext ➔ Decryption ➔ Plaintext

Caesar Cipher Example

  • Shift 3 Example:

    • Plaintext: CAT ➔ Ciphertext: ZXG

    • Transformation through systematic shifts in alphabets

Classification of Cryptographic Systems

  • Based on three dimensions:

  1. Type of operations: Substitution vs. transposition

  2. Number of keys:

    • Symmetric or Conventional Encryption: Same key for sender & receiver

  3. Processing method:

    • Block Cipher: Processes blocks of data at once

    • Stream Cipher: Processes data as a continuous stream

Steganography

  • Definition: Hiding the existence of a message

  • Methods of conveying hidden messages:

    • Use first letters or selected words of others to spell hidden content

  • Examples of historical techniques:

    • Character marking

    • Invisible ink

    • Pin punctures

    • Typewritten correction ribbon

  • Drawbacks of Steganography:

    • High overhead for limited data hiding

    • Vulnerable once discovered

Security Mechanisms

  • Key mechanism: Cryptography

  • Common security methods include:

    1. Encipherment

    2. Digital Signature

    3. Access Control

Categories of Security Attacks

  1. Interruption: Asset destruction or unavailability

  • Example: Hardware destruction, communication line cuts

  1. Interception: Unauthorized access to data

  • Example: Wiretapping, illicit file copying

  1. Modification: Tampering with accessed data

  • Example: Data alteration, message content modification

  1. Fabrication: Inserting counterfeit elements into the system

  • Example: Fake messages, unauthorized record addition