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Symmetric encryption

  • The same key encrypts and decrypts the data
  • It's also known as secret-key encryption
  • The encryption key is generated directly from the password
  • It is not possible to change the password/key of already encrypted content. In this case the data has to be decrypted and encrypted with a different password

Encryption-only algorithms

AES (Advanced Encryption Standard)

  • Uses block cipher

  • encrypt fixed-size blocks (AES, DES, Twofish)

  • Most widely used today (TLS, VPNs, disk encryption, WiFi WPA2/WPA3)

  • Block cipher (operates on fixed-size blocks, usually 128 bits)

  • Key sizes:

  • 128 bits
  • 192 bits
  • 256 bits: AES256

ChaCha20

  • Uses stream cipher
  • encrypt data bit by bit or byte by byte (ChaCha20, RC4)

Signing-only algorithms

HMAC (Hash-based Message Authentication Code)

  • Used for signing / authentication (integrity + authenticity, but not encryption)
  • Keyed hashing scheme
  • Example algorithms:
  • HMAC-SHA256 (used in JWT HS256)
  • HMAC-SHA1

  • HMAC-SHA512

  • Variations

  • HS256 (HMAC with SHA-256)