Crypto systems

Hidden, Secret

Confidentiality

  • Especially with transport encryption

Authentication and access control

  • I know it's you. I really know it's you.

Non-repudiation

  • You said it. You can't deny it

Integrity

  • Tamper-proof

Cryptography terms

Cipher text - encrypted message

Cipher - algorithms

Plain text - unencrypted message

Cryptanalysis - art of cracking

Cryptography types

Transposition Cipher

Mechanical cipher (Enigma Machine)

Substitution cipher (Caesar cipher)

Mathematical Ciphers

Cipher

Block ciphers

  • Symmetric encryption
  • not used in asymmetric encryption
  • 64 pr 128 bit
  • most widely used
    Advantages
    -- Diffusion
    -- Immunity to insertion
    Disadvantages
    -- Slowness of encryption
    -- Error propagation

Stream ciphers

  • process one bit at a time
  • Vernam cipher, one time pad
    Advantages
    -- Speed of transformation
    -- Low error propagation
    Disadvantages
    -- Low diffusion
    -- Susceptibility to malicious insertion and modifications

Symmetric Encryption Ciphers

DES and 3DES

  • DES - Data Encryption Standard
  • 64 bit block cipher (56 bit key)
  • 3DES - Encrypt with DES three times
  • Three keys, two keys or same key three times

AES

  • Advance Encryption Standard
  • 128-bit block cipher
  • 128, 192 and 256 bit keys
  • Used in WPA2 (Powerful wireless encryption)

Public key encryption systems

  • Asymmetric key
  • digital signature - verify a message comes intact from the claimed sender
  • Public key - known by anybody and can be used to encrypt the messages, verify signature
  • Private key - known only to the recipient, used to decrypt message and sign signatures

RSA

Diffie-Hellman

Knapsack based encryption

DSS - Digital Signature Standard

ECC - Elliptic Curve Cryptography

  • not less secure than RSA or some other public key crypto algorithms
  • with smaller key size achieve same security as RSA
  • more efficient for secure wireless applications
  • high scalability
  • more potential due to EC theory

DSA - Digital Signature Algorithm

Other symmetric block ciphers

  • IDEA - International Data Encryption Algorithm
  • Blowfish
  • RC5
  • Cast-128