FIAS

Cryptography and Network Security

  • Importance of Cryptography: Protect data during transmission; modifies information to prevent unauthorized access.

Security Types

  • Computer Security: Tools to protect data from unauthorized access.

  • Network Security: Protects data during transmission across networks.

  • Internet Security: Protects data in interconnected networks.

Security Attacks, Services, and Mechanisms

  • Security Attack: Any act compromising an organization's data security.

  • Security Mechanism: Tools to detect, prevent, or recover from security attacks.

  • Security Service: Enhances data processing security; counters attacks.

Basic Cryptographic Concepts

  • Plaintext: Original intelligible message.

  • Ciphertext: Transformed unintelligible message.

  • Cipher: Algorithm for transforming plaintext.

  • Key: Critical information used for the cipher, known only to sender/receiver.

Processes

  • Encipher (Encode): Converts plaintext to ciphertext.

  • Decipher (Decode): Converts ciphertext back to plaintext.

  • Cryptanalysis: Study of breaking cipher without key; also called code breaking.

Cryptographic Systems Classification

  1. Type of Operations: Substitution (replaces elements) & Transposition (rearranges elements).

  2. Number of Keys: Symmetric (same key) vs Public key encryption (different keys).

  3. Processing Method: Block cipher (processes data in blocks) vs Stream cipher (processes data continuously).

Cryptanalysis Techniques

  • Ciphertext Only: Only ciphertext is known to cryptanalyst.

  • Known Plaintext: Both ciphertext and corresponding plaintext are known.

  • Chosen Plaintext: Access to the encryption machine to encrypt chosen plaintexts.

  • Chosen Ciphertext: Access to the decryption machine to decrypt chosen symbols.

Security Services

  • Confidentiality: Information is accessible only to authorized parties.

  • Authentication: Identifies the source of data accurately.

  • Integrity: Ensures modifications are made only by authorized parties.

  • Non-repudiation: Neither sender nor receiver can deny message transmission.

  • Access Control: Regulates access to information resources.

  • Availability: Ensures system assets are accessible when needed.

Security Attacks Categories

  1. Interruption: System asset becomes unavailable (e.g., hardware destruction).

  2. Interception: Unauthorized access to an asset (e.g., wiretapping).

  3. Modification: Tampering with an asset (e.g., altering data).

  4. Fabrication: Inserting counterfeit objects into the system (e.g., spurious messages).

Active vs. Passive Attacks

  • Passive Attacks: Eavesdropping or monitoring (not altering data).

    • Types: Message content release, traffic analysis.

  • Active Attacks: Modification or creation of false data streams.

    • Categories: Masquerade, Replay, Message Modification, Denial of Service.

Classical Encryption Techniques

  • Substitution Techniques: Replace plaintext letters with other characters.

  • Caesar Cipher: Shifts letters by a fixed number (e.g., "pay more money" to "SDB PRUH PRQHB").

Importance of Cybersecurity

  • Protects sensitive data from theft via cyber threats; increasingly critical due to reliance on technology and cloud services.

  • Growing threat landscape includes social engineering, ransomware, and cloud vulnerabilities.

  • Data breaches can cause significant financial loss and reputation damage; legal repercussions include GDPR compliance.

Trends in Cybersecurity

  • Increased focus on data breach notifications and regulatory compliance.

  • Rising costs of cybercrime; average breach cost now over $13 million in organizations.