Crunch

Password Attacks

Beginnerlow risk

Crunch is a wordlist generator where you can specify a standard character set or a custom one. It can generate all possible combinations.

Installation

sudo apt install crunch

Basic Syntax

crunch <min> <max> [charset] -o <output>

Quick Facts

Full Name

Crunch

License

GPLv2

Author

Bohannon (various maintainers)

Written In

C

Platforms

Linux, macOS

Category

Wordlist Generation

Generation Method

Pattern-based (character sets)

Output

File or stdout (pipeable)

Tool Overview

Crunch is a wordlist generator that creates every possible character combination within specified parameters. It generates wordlists from minimum and maximum lengths, custom character sets, and pattern templates.

Unlike content-based tools like CeWL, Crunch creates wordlists mathematically. You define the character set (lowercase, uppercase, digits, symbols) and length range, and Crunch generates all permutations. This makes it ideal for creating PIN lists, brute-force dictionaries, and pattern-based wordlists.

Crunch can output directly to files or stdout, allowing it to pipe directly into other tools like Hashcat, John the Ripper, or Hydra without creating intermediate files.

Common Commands

crunch 6 6Generate all lowercase words of exactly 6 characters using the default charset

crunch 4 8Generate words from 4 to 8 characters long using the default lowercase charset

crunch 8 8 abcdefghijklmnopqrstuvwxyzGenerate 8-char words using a custom lowercase-alphabet charset

crunch 6 6 0123456789Generate all 6-digit numeric PIN combinations

crunch 6 8 -o wordlist.txtWrite generated 6-8 char words to a file instead of stdout

crunch 1 8 -f /usr/share/crunch/charset.lst mixalpha -o wordlist.txtUse a named charset from charset.lst and save to a file

crunch 8 8 -t @@@@@@@@ -o pass.txtUse a pattern of lowercase-letter placeholders to build the wordlist

crunch 12 12 -t Pass@@@@%%%%Build passwords with a fixed prefix plus lowercase and numeric placeholders

crunch 10 10 -t @@@@@^^^^^Generate words mixing lowercase letters and symbols via pattern placeholders

crunch 8 8 -t pass,%%%Use uppercase-letter placeholder (,) followed by numeric placeholders in a pattern

crunch 6 6 abcdef -s cadefStart generating from a specific word rather than the first combination

crunch 6 6 abc123 -e fff123Stop generating once a specific end word is reached

crunch 4 6 abc -d 2@ -o wordlist.txtLimit consecutive identical characters (max 2 of the same @ placeholder)

crunch 1 6 abcABC -c 1000 -o STARTSplit output into files of 1000 lines each (START is auto-renamed by content)

crunch 6 8 -b 20mib -o STARTSplit output into files no larger than 20 MiB each

Step-by-Step Guide

1Establish the minimum and maximum lengths for your requirements
2Pick the specific alphabet or numbers you wish to include
3Define the parameters within the command line
4Incorporate specific patterns if you know part of the string
5Execute the generation sequence

Warnings

Broad parameters will generate files that exceed your hard drive capacity
Ensure you have sufficient storage space before executing
Rely on known patterns to keep the file size manageable

Use Cases

PIN Generation

Generate all 6-digit numeric PINs for testing PIN-based authentication systems.

Pattern-Based Dictionaries

Create wordlists matching known password patterns like 'pass' + 4 digits.

Brute-Force Input

Pipe generated words directly into cracking tools without intermediate files.

Brute-Force Dictionaries

Generate complete character set combinations for exhaustive password testing.

CTF Challenges

Create custom wordlists for cryptography and password cracking challenges.

Key Features

Character Set Generation: Generate all combinations from custom character sets (letters, digits, symbols).
Pattern Templates: Use @, , %, ^ placeholders for structured password generation.
Stdout Piping: Stream output directly to other tools without intermediate files.
File Output: Save generated wordlists to files with the -o flag.
Size Limits: Control output size with -b flag (e.g., -b 1gb for 1GB chunks).
Position Filtering: Generate only specific positions within patterns for targeted output.

Output Explanation

Outputs a text file populated with every single mathematical permutation based on your input parameters.

Ethical Usage Notice

This tool is designed for authorized security testing, educational purposes, and legitimate network administration only. Unauthorized access to computer systems is illegal.