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COMP3632 (Cryptography (SKE(Symmetric/Secret Key Encryption) (Block Cipher…

- - - - IV(Initialization Vector)
  - - - Perfectly Secure if:
        Key is never reused
        Key is truly uniformly random
      - VENONA Project(1943)
    - - Generates keystream of any length from random seed
        
        A5/1 (cell phones)
        
        RC4 (Internet)
      - Continuous process
    - - fixed block size
      - DES(56-bit)
        
        shown to be too weak in 1998 (Deep crack cracker)
      - AES(128-bit)
        
        Suitable when the amount of data
        is known beforehand
      - Mode
        
        ECB(Electronic codebook)
        
        No IV, all key are the same
        (no defense against duplicate ciphertext)
        
        Default yet insecure
        
        CBC(Cipher Block Chaining)
        
        Plaintext block x xor with Ciphertext block (x-1) before encryption
        
        CTR(Counter)
        
        Use IV: Plaintext block x xor IV
        then encrypted with key and ciphertext block (x-1)
  - - - Anyone can encrypt
        Only Alice can decrypt
    - - Requires much longer keys (2048/4096 bits)
      - Can be broken by quantum computers
  - - - irreversible one-way functions
      - MD5(insecure!), SHA1, SHA2, SHA3
      - Precompute hash table
        
        Salt
      - During file transmission
        
        send M, h(M)
        
        Attacker can send M', h(M')
  - - - attached to messages for authentication
      - The two parties both need to have the secret key
      - Authenticates the sender and the message
      - Can be built from a hash (HMAC)
  - - - sign/verify keys are long-lasting while
        encrypt/decrypt keys are short-lived
  - - - TOFU(Trust on first use)
    - - Web of Trust
        
        Transitive
- - - - Self replicates among files
      - To avoid detection
        
        Code polymorphism
        
        Hide in boot sector
        
        Interrupt scanning techniques
      - Examples
        
        ILOVEYOU(2000, Windows)
        
        ByteBandit(1987, Amiga)
    - - Self replicates across network
      - Needs no user action
      - Examples
        
        Slammer Worm(2003, Windows)
        
        this is a "Warhol Worm"
        
        SQL Servers
        
        Blaster Worm(2003, Windows)
        
        Wechia is another worm that removes Blaster and forces install patches
        
        Morris Worm(1988, Unix)
        
        Conficker Worm(2008, Windows)
        
        Botnet
    - - Trick user into installing
      - Packaged with useful software
      - Looks like useful software
        
        Android repackaging
      - Scareware
      - Zip bomb, email bomb, compiler bomb
      - Spear phishing
    - - Installed intentionally
      - No automatic spreading
      - Espionage
      - Angry employee
      - Logic bomb
      - Attacker has temporary control over the system
  - - - Command & Control system
      - Master & Bots
      - Attack with other bots
    - - Steal private data
      - Trackers
        
        Cookies
        
        First Party
        
        Third Party
        
        Web bugs
        
        Cookie syncing
    - - Record keystrokes
      - Types
        
        Application-specific keyloggers
        
        Software keyloggers
        
        Hardware keyloggers
    - - Ransom data
    - - Allow unrestricted access
    - - Hide further attacks
      - Greek wiretapping case(04-05)
      - Sony XCP
  - - - 4 zero-day attacks
  - - - Signature-based
      - Behavior-based(heuristics)
    - - Static
      - Dynamic
      - Formal verification
      - sel4: Formally verified OS
    - - Unit testing (test small unit)
      - Integration testing (test integration of units)
      - Fuzz testing (test with random input)
      - Black-box testing (test unknown system)
      - White-box testing (test known system)
      - Regression testing (test if update causes bugs)
    - - Guided Code Review
      - Pair programming
      - Fagan review
      - Change management
- - - - Protection: Anonymization, disassociation
- - - - Informational Theory
      - Computational theory
    - - E.g. authentication
    - - Freeze and take out RAM
    - - Special characters
  - - - Keylogger
- - - - Heartbleed
    - - KISS(Keep It Simple/Stupid)
    - - 2 factor authentication
- - - - Buffer overread
        
        Heartbleed
      - Buffer overflow
        
        strcpy, gets, fgets
        
        Defenses
        
        Never execute code on stack
        
        W^X(Write xor Execute)
        
        NX
        
        DEP
        
        Defeat: Return-Oriented Programming
        
        Randomize Stack
        
        Address Space Layout Randomization(ASLR)
        
        Detect overflow
        
        Canaries
        
        Do not use C
        
        Related attacks
        
        Integer overflow
        
        Format String Vulnerability
        
        writing into buffers using printf instead of strcpy
        
        %n -> number of characters before it
      - TOCTTOU(time of check to time of use)
    - - XSS(Cross-site Scripting)
        
        Persistent XSS vulnerability
        
        Reflected XSS vulnerability
      - XSRF(Cross Site Request Forgery)
      - SQL Injection
    - - Canonicalization
  - - - Covert channels
        
        TCP initial sequence number
        
        size of packets
        
        timing
        
        port knocking
      - Side channels
        
        Power analysis
        
        Timing analysis
        
        EM wave analysis
        
        Acoustic analysis
        
        Defense
        
        Air gap
        
        Faraday cage
- - - - SLE(Single Loss Expectancy)
        
        Asset Value*Exposure Factor
      - ALE(Annual Loss Expectancy)
        
        SLE*annualized rate of occurence