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Authentication Systems. CS 470 Introduction to Applied Cryptography Instructor: Ali Aydin Selcuk. Entity Authentication. Authentication of people, processes, etc. Non-cryptographic Address-based (E-mail, IP, etc.) Passwords Biometrics Cryptographic Symmetric key Public key.

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authentication systems

Authentication Systems

CS 470

Introduction to Applied Cryptography

Instructor: Ali Aydin Selcuk

Authentication Systems

entity authentication
Entity Authentication
  • Authentication of people, processes, etc.
  • Non-cryptographic
    • Address-based (E-mail, IP, etc.)
    • Passwords
    • Biometrics
  • Cryptographic
    • Symmetric key
    • Public key

Authentication Systems

authentication tokens
Authentication Tokens
  • What you know (password schemes)
  • What you have (keys, smart cards, etc.)
  • What you are (fingerprints, retinal scans, etc.)

Authentication Systems

password problems
Password Problems
  • Eavesdropping
  • Stealing password files
  • On-line password guessing
  • Off-line guessing attacks
    • Dictionary attacks
    • Exhaustive search
  • Careless users writing down passwords

Authentication Systems

on line password guessing
On-line Password Guessing

Careless choices (first names, initials, etc.); poor initial passwords

Defenses: After wrong guesses,

  • Lock the account
    • Not desirable, can be used for DoS
  • Slow down
  • Alert users about unsuccessful login attempts
  • Don’t allow short or guessable passwords

Authentication Systems

off line password guessing
Off-line Password Guessing
  • Stealing & using password files
  • Passwords should not be stored in clear.Typically, they’re hashed and stored.
  • Attacks:
    • Exhaustive search
    • Dictionary attacks
  • Defenses:
    • Don’t allow short/guessable passwords
    • Don’t make password files readable
    • Salting: Mix a random number to each hash

Authentication Systems

eavesdropping
Eavesdropping
  • Watching the screen
  • Watching the keyboard
  • Login Trojan horses
    • Different appearance
    • Interrupt command for login
  • Keyboard sniffers
    • Good system administration
  • Network sniffers
    • Cryptographic protection
    • One-time passwords

Authentication Systems

initial password distribution
Initial Password Distribution
  • Initial off-line authentication
  • Passwords can be chosen on site by users
  • An initial password can be issued by the system administrator.
  • Pre-expired passwords: Has to be changed at the first login

Authentication Systems

authentication tokens1
Authentication Tokens
  • Keys (physical)
  • ATM, credit cards
  • Smart cards: On-card processor for cryptographic authentication.
    • PIN-protected cards: Memory protected by PIN
    • Challenge-response cards: Performs challenge-response authentication through SC reader
      • New technology: Tokens working through USB ports.
    • Cryptographic calculator
      • Current time encrypted, displayed to user, entered to terminal
      • Adv: Access through standard terminals

Authentication Systems

biometrics
Biometrics
  • Authentication by inherent physical characteristics
  • E.g., fingerprint readers, retina/iris scanners, face recognition, voice recognition
  • Problems:
    • Expensive
    • Not fault tolerant
    • Can be replayed in remote authentication

Authentication Systems

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