Crypto

• deterministic encrypt -  same c for a given pt and key

• probabilistic encrypt - encrypting same pt multiple times gives dif c

• can use nonce to add a random factor to encryption

  • e.g. Initialization Vector
  • salt is associated w password hashing

luv [[RSA]]

[[PFS]]

• digital signatures

  • integrity
  • auth
  • non-repudiation

• key stretching done w

  • Bcrypt - based on blowfish
  • PBKDF2 - used by [[WPA]]2 and iOS

encryption

• homomorphic encryption -> ciphertext can still be used and worked with as if plaintext [[symmetric encryption]] asymmetric encryption

ciphers

• stream - enc done one bit or byte at time
• block - block done at a type (usually 64 or 128 bit)
  • block cipher modes
    • ECB - use same key for each block
    • CBC (cipher block chaining) - each block XORed w previous block + add random IV
    • CTR - ECB but key is a counter
    • GCM - enc w auth
      • seen in IPsec, [[SSH]], [[SSL-TLS]]