Security Architecture and Engineering · Topic 6 of 8
Cryptanalytic Attacks
Attacks on cryptography: brute force, known plaintext, side channels, timing, fault injection, man-in-the-middle, pass the hash, Kerberos and ransomware.
- 3 min
- Brute force is beaten by key length; birthday attacks by hash length.
- Salts defeat rainbow tables; slow hashing slows guessing.
- Side-channel, timing and fault injection attack implementations, not algorithms.
What it is
Cryptanalysis is the study of breaking cryptographic protection. Most real attacks do not break strong algorithms; they target weak keys, poor implementations, side effects of the hardware or the people and processes around the cryptography.
How it works
Attacks on algorithms and keys
| Attack | Attacker has | Idea |
|---|---|---|
| Brute force | Ciphertext | Try every key; defeated by long keys |
| Ciphertext only | Only ciphertext | Look for patterns |
| Known plaintext | Some plaintext and its ciphertext | Derive the key from the pair |
| Chosen plaintext | Ability to encrypt chosen inputs | Study how outputs change |
| Chosen ciphertext | Ability to decrypt chosen ciphertexts | Learn about the key or plaintext |
| Frequency analysis | Ciphertext from simple ciphers | Common letters reveal substitutions |
| Birthday attack | Many hash outputs | Find two inputs with the same hash faster than expected; defeated by longer hashes |
| Dictionary and rainbow tables | Stolen password hashes | Precomputed guesses; defeated by salting and slow hashing |
Attacks on implementations and hardware
| Attack | Idea | Mitigation |
|---|---|---|
| Implementation attacks | Exploit coding errors, weak random numbers, poor padding handling | Vetted libraries, testing |
| Side-channel | Measure power use, electromagnetic emissions, sound or timing | Constant-time code, shielding, noise |
| Timing | Infer secrets from how long operations take | Constant-time comparisons and algorithms |
| Fault injection | Cause errors with voltage, clock or laser glitches to leak keys | Tamper-resistant hardware, error checking |
Attacks on protocols and credentials
| Attack | Idea | Mitigation |
|---|---|---|
| Man-in-the-middle (on-path) | Intercept and relay or alter traffic | Mutual authentication, certificate validation |
| Replay | Resend captured valid messages | Nonces, timestamps, session tokens |
| Pass the hash | Use a stolen password hash to authenticate without the password | Limit admin credential exposure, credential guards, unique local admin passwords |
| Kerberos exploitation | Abuse tickets (for example golden or silver tickets, or cracking service ticket hashes) | Protect domain controllers, rotate the KRBTGT account, strong service account passwords, monitoring |
| Downgrade | Force use of weaker protocol versions or ciphers | Disable old versions, enforce minimums |
Ransomware
Ransomware uses cryptography offensively: strong encryption of the victim's data with keys the attacker holds. The defense is not cryptanalysis but resilience: immutable or offline backups, segmentation, rapid detection, and protecting administrative credentials.
People and process attacks
The easiest path is often social engineering or theft of keys. Rubber-hose cryptanalysis (coercion) and purchase of keys bypass the mathematics entirely. Key management and personnel security matter as much as algorithm strength.
When a question asks for the best defense against a cryptanalytic attack, match it: salting against rainbow tables, longer keys against brute force, constant-time code against timing, nonces against replay.
Quantum computing risk
Large quantum computers could break today's RSA, Diffie-Hellman and ECC. Data with a long confidentiality life is at risk of "harvest now, decrypt later". Plan migration to quantum-resistant algorithms and keep cryptography agile so algorithms can be swapped.
How the exam asks about this
- "An attacker uses precomputed hash tables on stolen password hashes." Rainbow table attack; defend with salts.
- "Measuring power consumption reveals the key." Side-channel attack.
- "An attacker authenticates with a captured NTLM hash." Pass the hash.
What to remember for the exam
- Brute force is beaten by key length; birthday attacks by hash length.
- Salts defeat rainbow tables; slow hashing slows guessing.
- Side-channel, timing and fault injection attack implementations, not algorithms.
- Nonces and timestamps defeat replay; mutual authentication defeats MITM.
- Ransomware is countered by resilient backups and detection.
A strong algorithm with poor key management is weak. Attackers usually go after the keys rather than the algorithm.
Common mistakes
Thinking encryption alone stops ransomware. Backups and segmentation do.
Confusing known plaintext with chosen plaintext.
Ignoring implementation flaws when the algorithm is strong.
Check yourself
What defeats rainbow table attacks on password hashes?
Unique salts, ideally with a slow password hashing algorithm.
Which attack infers keys from how long operations take?
A timing attack, a kind of side-channel attack.
What attack uses a captured password hash to log in without knowing the password?
Pass the hash.
Topic 6 of 8 in Security Architecture and Engineering
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