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Cryptography and Security Fundamentals

Cryptography and Security Fundamentals encompass the core principles, algorithms, and protocols used to protect information confidentiality, integrity, and availability in digital systems.^[001-TODO__28490作日誌寫入機制.md] This field ensures that data remains secure against unauthorized access, tampering, and other cyber threats.

Core Concepts

The study of cryptography and security relies on balancing mathematical theory with practical implementation to safeguard systems.

Confidentiality, Integrity, and Availability

The CIA Triad is the fundamental model for information security: * Confidentiality: Ensuring that information is accessible only to authorized individuals. * Integrity: Maintaining the accuracy and completeness of data, protecting it from unauthorized modification. * Availability: Ensuring that authorized users have reliable and timely access to information and resources.

Encryption Algorithms

Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) to prevent unauthorized access^[001-TODO__28490作日誌寫入機制.md]. It is categorized into two main types:

  • Symmetric Encryption: Uses a single shared secret key for both encryption and decryption. It is generally faster and suitable for encrypting large amounts of data. Common algorithms include AES (Advanced Encryption Standard).
  • Asymmetric Encryption: Uses a public key pair (a public key for encryption and a private key for decryption). This facilitates secure key exchange and digital signatures without sharing a secret. Common algorithms include RSA and ECC (Elliptic Curve Cryptography).

Hashing

Hashing algorithms convert data of arbitrary size into a fixed-size string of characters, which is typically a digest that uniquely represents the input^[001-TODO__28490作日誌寫入機制.md]. Unlike encryption, hashing is a one-way function and cannot be reversed^[001-TODO__28490作日誌寫入機制.md].

  • Properties:
    • Deterministic: The same input always yields the same hash.
    • Avalanche Effect: A small change in the input drastically changes the hash.
    • Collision Resistance: It should be computationally infeasible to find two different inputs that produce the same hash.
  • Use Cases:
    • Password Storage: Passwords are often hashed with salt (random data) to protect them even if the database is compromised^[001-TODO__28490作日誌寫入機制.md].
    • Data Integrity: Verifying that data has not been altered (e.g., file checksums).

Sources

  • 001-TODO__28490作日誌寫入機制.md