CISSP 7.8 - Cryptographic Attacks

This episode of the ISC2 Certified Information Systems Security Professional (CISSP) exam prep series maps the attacks against cryptosystems in Domain 3 — how adversaries pressure keys, algorithms, implementations, and even the physical behavior of machines, and why understanding each technique points you straight to the defense that neutralizes it, on the exam and on the job.

Frequently Asked Questions

How do attackers grind through keys by brute force?

A brute-force attack simply tries every possible key or password until one works, leaning on raw processing power, and given enough time it always eventually succeeds. The cost is tied to key length, since each extra bit doubles the number of possible keys and so doubles the time required. Attackers speed things up with rainbow tables, which are precomputed hashes handy for cracking stored passwords, and with specialized hardware built for the task.

How do you blunt a brute-force attack on passwords?

The key defense is salting: a random value added to a password before it is hashed, stored alongside the resulting hash. Because each password gets its own salt, an attacker cannot reuse one precomputed rainbow table across everyone, and would need a separate table for every possible salt. Layer on key stretching, used by specialized password hashing functions, and each single guess becomes deliberately slow and expensive.

What are side-channel attacks and their cousins?

These attacks watch the machine rather than the message. A side-channel attack monitors characteristic signals a computer leaks as it works, like changing power draw, processor load, or electromagnetic emissions, to pull out information being encrypted. A timing attack is a specific flavor that measures exactly how long cryptographic operations take to infer secrets, and a fault injection attack deliberately stresses a device with extreme voltage or temperature to force a malfunction that weakens its security.

How do meet-in-the-middle and man-in-the-middle differ?

The meet-in-the-middle attack targets encryption that runs in two rounds: the attacker encrypts a known plaintext under every possible first key and decrypts the ciphertext under every possible second key, looking for a match that reveals both keys, which is why doubling a cipher’s rounds adds far less protection than you would hope. The man-in-the-middle attack is about interception, where the attacker secretly sits between two parties, sets up a separate secure session with each, and relays traffic while reading everything. One breaks double encryption, the other hijacks a conversation.

What other classic attacks should you recognize?

A birthday attack, or collision attack, hunts for two different messages that produce the same hash, letting an attacker swap in a substitute message that still matches a valid signature. A replay attack captures a legitimate encrypted message, often an authentication request, and sends it again later, defeated with timestamps and expiration, challenge-response, and ephemeral session keys. And never forget social engineering: talking someone into handing over a key beats cracking any cryptosystem the hard way.

Reference: This article is based on concepts discussed in CISSP 7.8 - Cryptographic Attacks.