Mastering Algorithms

Chapter 11: Encryption Algorithms

Introduction to Encryption

Encryption is the process of converting plaintext into ciphertext to protect data confidentiality. Encryption algorithms are fundamental to modern cybersecurity, enabling secure communication, data protection, and privacy. Understanding encryption algorithms is crucial for anyone working with secure systems, cryptography, or data protection.

This chapter covers some popular encryption algorithms, each serving different purposes in modern cryptography. These algorithms are categorized into:

  • Symmetric Encryption: AES, DES - Same key for encryption and decryption
  • Asymmetric Encryption: RSA - Different keys for encryption and decryption
  • Hash Functions: SHA, MD5 - One-way functions for data integrity

Encryption Algorithms

1. AES (Advanced Encryption Standard)

A symmetric encryption algorithm that is the current standard for encrypting data. It's fast, secure, and widely used in modern applications.

  • Type: Symmetric Block Cipher
  • Key Sizes: 128, 192, 256 bits
  • Block Size: 128 bits
  • Best For: General-purpose encryption, data protection

2. RSA (Rivest-Shamir-Adleman)

An asymmetric encryption algorithm based on the mathematical difficulty of factoring large prime numbers. Used for secure key exchange and digital signatures.

  • Type: Asymmetric Public-Key
  • Key Sizes: 1024, 2048, 4096 bits
  • Security: Based on integer factorization
  • Best For: Key exchange, digital signatures, SSL/TLS

3. DES (Data Encryption Standard)

A symmetric encryption algorithm that was the standard for many years but is now considered obsolete due to its small key size. Still studied for historical and educational purposes.

  • Type: Symmetric Block Cipher
  • Key Size: 56 bits (now insecure)
  • Block Size: 64 bits
  • Status: Deprecated, replaced by AES

4. SHA (Secure Hash Algorithm)

A family of cryptographic hash functions that produce fixed-size hash values. Used for data integrity verification, digital signatures, and password hashing.

  • Type: Cryptographic Hash Function
  • Variants: SHA-1, SHA-256, SHA-512
  • Output Size: 160-512 bits depending on variant
  • Best For: Data integrity, digital signatures, password hashing

5. MD5 (Message Digest 5)

A widely-used hash function that produces a 128-bit hash value. While fast, it's now considered cryptographically broken and should not be used for security purposes.

  • Type: Cryptographic Hash Function
  • Output Size: 128 bits
  • Status: Cryptographically broken
  • Use: Non-security applications, checksums

Algorithm Comparison

Algorithm Type Key/Hash Size Security Level Use Case
AES Symmetric 128-256 bits High Data encryption
RSA Asymmetric 2048+ bits High Key exchange, signatures
DES Symmetric 56 bits Low (deprecated) Historical/educational
SHA Hash Function 256-512 bits High Data integrity
MD5 Hash Function 128 bits Broken Non-security checksums

Algorithm Selection Guide

For Data Encryption:

  • Use AES - Modern standard, fast and secure

For Key Exchange and Digital Signatures:

  • Use RSA - Widely supported, secure for key exchange

For Data Integrity and Hashing:

For Legacy Systems:

  • DES - Only for compatibility, not recommended for new systems

What's Next?

Now that you understand encryption algorithms, explore related topics: