Password Cracking Lecture Flashcards

This set of vocabulary flashcards covers key concepts in password security and cracking, including hash function types, specific attack vectors, and defensive countermeasures described in the lecture.

Credential stuffing

The practice of using stolen username/password pairs from one breach to break into other services, a technique effective because 65% of people reuse passwords across multiple sites.

Hash Functions

One-way, irreversible cryptographic functions that produce the same output/hash value if identical content is passed through them.

Rainbow Table Attack

A cryptographic attack using a precomputed table of hash values for every possible password to significantly reduce the time needed to crack a password hash.

Salt

A random string added to a password before hashing so that even identical passwords produce completely different hashes, rendering rainbow tables ineffective.

MD5

A 128-bit hash function currently considered broken, as it can be crashed in less than $1$ second on a modern GPU.

SHA-1

A 160-bit hash function that has been deprecated since 2011 and is being phased out due to being weak.

SHA-256

A 256-bit secure hash function that serves as the standard for Bitcoin, TLS certificates, and modern security.

bcrypt

A secure 184-bit hash function designed to be slow to resist GPU cracking.

scrypt

A secure, memory-hard hash function designed to resist ASIC and GPU cracking.

yescrypt

A modern, secure version of scrypt (denoted by $y$) that is the current default on many Linux systems.

Linux Shadow File

The file where password hashes are stored in Linux, typically using the format algorithm$salt$hash.

Online Attack

An attack where passwords are tried against a live login page, which is very slow due to rate limiting and lockouts.

Offline Attack

A high-speed attack where stolen hashes are cracked on an attacker's machine, potentially reaching billions of guesses per second.

Hashcat

Frequently called the world’s fastest password cracker, it is a tool used for offline cracking of stolen hashes.

Bruteforce Attack

An attack that tries every possible combination of characters within a given keyspace and is guaranteed to find the password eventually.

Mask Attack

A smarter, faster version of bruteforce where the attacker provides Hashcat with a specific pattern or pattern markers like $?l$ for lowercase or $?d$ for digits.

Dictionary Attack

An attack that takes a precompiled list of common words or passwords, such as rockyou.txt, and tries each one against the target hash.

Rule-Based Attack

An attack that takes dictionary words and modifies them using transformation rules like capitalization, leet speak (e.g., $a \rightarrow @$), or appending numbers.

Hybrid Attack

An attack combining a dictionary (list of base words) with a mask (rules for appending or prepending characters).

Lazarus Group

A state-sponsored hacker group that stole hundreds of millions in cryptocurrency by exploiting weak passwords and phishing.