OBJECTIVE 06 — CRYPTOGRAPHY ATTACKS AND CRYPTANALYSIS

WHAT IS CRYPTANALYSIS (EXAM DEFINITION)

Term Definition
Cryptanalysis The process of analyzing cryptographic systems to discover weaknesses and recover plaintext or keys without authorization

MEMORY HOOK:
Cryptoanalysis = breaking crypto

GOALS OF CRYPTANALYSIS

Goal
Recover plaintext
Discover secret keys
Bypass cryptographic protections

CLASSIFICATION OF CRYPTOGRAPHY ATTACKS (EXAM FAVORITE)

BASED ON ATTACKER KNOWLEDGE

CIPHERTEXT-ONLY ATTACK (COA)

Property Description
Attacker has Only ciphertext
Goal Recover plaintext
Difficulty Hardest

MEMORY HOOK:
Ciphertext only = blind attack

KNOWN-PLAINTEXT ATTACK (KPA)

Property Description
Attacker has Plaintext + ciphertext pairs
Goal Recover key
Example Known file headers

MEMORY HOOK:
Known plaintext leaks structure

CHOSEN-PLAINTEXT ATTACK (CPA)

Property Description
Attacker can Choose plaintext
Observes Ciphertext
Example Encryption oracle

MEMORY HOOK:
Chosen input = strong attacker

CHOSEN-CIPHERTEXT ATTACK (CCA)

Property Description
Attacker can Choose ciphertext
Observes Decrypted output
Example Padding oracle

MEMORY HOOK:
Chosen ciphertext = very powerful

BRUTE-FORCE ATTACK

Property Description
Method Try all possible keys
Effective against Small key sizes
Prevented by Strong keys

MEMORY HOOK:
Short key = brute-force bait

DICTIONARY ATTACK

Property Description
Method Guess keys/passwords
Uses Wordlists
Target Weak passwords

RAINBOW TABLE ATTACK

Property Description
Target Password hashes
Method Precomputed hash tables
Defense Salting

MEMORY HOOK:
Salt defeats rainbow tables

BIRTHDAY ATTACK (VERY HIGH YIELD)

WHAT IS A BIRTHDAY ATTACK

Concept Explanation
Based on Birthday paradox
Targets Hash functions
Goal Find collisions

LOGIC:

  • Easier to find collisions than reverse hashes

EXAM RULE:

  • For n-bit hash, collision resistance ≈ 2^(n/2)

MEMORY HOOK:
Hash length ÷ 2 = collision effort

COLLISION ATTACK

Property Description
Goal Two inputs → same hash
Affects MD5, SHA-1
Impact Digital signature forgery

MAN-IN-THE-MIDDLE (MITM) IN CRYPTO

Property Description
Target Key exchange
Affects Diffie-Hellman
Defense Authentication

MEMORY HOOK:
DH without auth = MITM risk

SIDE-CHANNEL ATTACKS (IMPORTANT)

WHAT IS A SIDE-CHANNEL ATTACK

Explanation
Exploits physical information leakage

TYPES OF SIDE-CHANNEL ATTACKS

Type Leakage
Timing attack Execution time
Power analysis Power consumption
EM analysis Electromagnetic signals
Acoustic Sound

MEMORY HOOK:
Not math, physics

PADDING ORACLE ATTACK (VERY IMPORTANT)

WHAT IT TARGETS

Target
Block cipher modes
CBC mode

HOW IT WORKS (HIGH-LEVEL)

Step
Observe padding error messages
Modify ciphertext
Infer plaintext

EXAM TRAP:
Error messages leak information.

MEMORY HOOK:
Errors leak secrets

DOWNGRADE ATTACK

Property Description
Goal Force weak crypto
Example SSL → TLS downgrade
Defense Disable legacy protocols

MEMORY HOOK:
Backward compatibility = weakness

REPLAY ATTACK

Property Description
Method Reuse captured data
Target Authentication protocols
Defense Nonces, timestamps

MEMORY HOOK:
Replay stops with freshness

CRYPTOGRAPHY MISCONFIGURATION ATTACKS

Misconfiguration
Weak algorithms
Short keys
Poor randomness
Reused IVs
ECB mode

MEMORY HOOK:
Crypto fails in implementation

COMMON CRYPTOGRAPHY TOOLS (CEH RECOGNITION)

CRYPTANALYSIS TOOLS

Tool Purpose
Hashcat Password cracking
John the Ripper Password cracking
Cain & Abel Credential recovery
OpenSSL Crypto operations
CrypTool Learning cryptography

OPENSSL COMMANDS (RECOGNITION ONLY)

Command Purpose
openssl enc Encrypt/decrypt
openssl dgst Hash generation
openssl genrsa Generate RSA key
openssl req Create CSR

MEMORY HOOK:
OpenSSL = crypto Swiss army knife

OBJECTIVE 06 — EXAM MEMORY BLOCK

Cryptanalysis exploits weaknesses in algorithms, keys, and implementations.
Birthday attacks target hash collisions.
MITM attacks exploit unauthenticated key exchange.
Side-channel attacks exploit physical leakage.
Padding oracle attacks exploit error messages.
Salting, authentication, and strong algorithms mitigate attacks.

MODULE 20 — FINAL CHECKLIST (VERY IMPORTANT)

You must remember:

  • Hash collision = birthday attack

  • Diffie-Hellman vulnerable to MITM

  • MD5 and SHA-1 broken

  • AES is secure

  • ECC uses smaller keys

  • PKI solves trust problem

  • CRL vs OCSP

  • Padding oracle targets CBC

  • Salt defeats rainbow tables

MODULE 20 STATUS

Section Status
Objective 01 COMPLETE
Objective 02 COMPLETE
Objective 03 COMPLETE
Objective 04 COMPLETE
Objective 05 COMPLETE
Objective 06 COMPLETE

You have now fully completed Module 20 – Cryptography.

Next options:

  • Module 20 ultra-condensed exam cheat sheet

  • Full CEH mock exam questions (crypto-heavy)

  • Continue to next CEH module

  • PKI-only drill with scenarios