John the Ripper

Here is a sample output in a Debian environment.

$ cat pass.txt

user:AZl.zWwxIh15Q

$ john -w:password.lst pass.txt

Loaded 1 password hash (Traditional DES [24/32 4K])

example (user)

guesses: 1 time: 0:00:00:00 100% c/s: 752 trying: 12345 - sandwich

The first line is a command to expand the data stored in the file "pass.txt". The next line is the contents of the file, i.e. the user (AZl) and the hash associated with that user (zWwxIh15Q). The third line is the command for running John the Ripper utilizing the "-w" flag. "password.lst" is the name of a text file full of words the program will use against the hash, pass.txt makes another appearance as the file we want John to work on.

Then we see output from John working. Loaded 1 password hash — the one we saw with the "cat" command — and the type of hash John thinks it is (Traditional DES). We also see that the attempt required one guess at a time of 0 with a 100% guess rate.

{{More citations needed section|date=November 2024}}

One of the modes John can use is the dictionary attack.{{Cite web |title=john/doc/MODES at bleeding-jumbo · openwall/john |url=https://github.com/openwall/john/blob/bleeding-jumbo/doc/MODES |access-date=2024-10-30 |website=GitHub |language=en}} It takes text string samples (usually from a file, called a wordlist, containing words found in a dictionary or real passwords cracked before), encrypting it in the same format as the password being examined (including both the encryption algorithm and key), and comparing the output to the encrypted string. It can also perform a variety of alterations to the dictionary words and try these. Many of these alterations are also used in John's single attack mode, which modifies an associated plaintext (such as a username with an encrypted password) and checks the variations against the hashes.

John also offers a brute force mode, dubbed "incremental mode". In this type of attack, the program goes through all the possible plaintexts, hashing each one and then comparing it to the input hash. John uses character frequency tables to try plaintexts containing more frequently used characters first. This method is useful for cracking passwords that do not appear in dictionary wordlists, but it takes a long time to run.

In addition to wordlist mode and incremental mode, there is :

• Markov mode — uses research by Arvind Narayanan and Vitaly Shmatikov{{Cite web |title=john/doc/MARKOV at bleeding-jumbo · openwall/john |url=https://github.com/openwall/john/blob/bleeding-jumbo/doc/MARKOV |access-date=2024-10-30 |website=GitHub |language=en}}{{Citation |title=Fast Dictionary Attacks on Passwords Using Time-Space Tradeoff |vauthors=((Narayanan, A.)), ((Shmatikov, V.)) |year=2005 |url=http://www.cs.utexas.edu/~shmat/shmat_ccs05pwd.ps |access-date=30 October 2024}}{{Cite book |last1=Narayanan |first1=Arvind |last2=Shmatikov |first2=Vitaly |chapter=Fast dictionary attacks on passwords using time-space tradeoff |date=2005-11-07 |title=Proceedings of the 12th ACM conference on Computer and communications security |chapter-url=https://dl.acm.org/doi/10.1145/1102120.1102168 |language=en |publisher=ACM |pages=364–372 |doi=10.1145/1102120.1102168 |isbn=978-1-59593-226-6}} to create candidates
• Mask mode — uses a user-supplied pattern to create candidates
• "Single crack" mode — uses details like the user's login name, full name, home directory name, et al. as candidates
• Subsets mode — generates candidates based on complexity, prioritising longer simple passwords over shorter complex ones
• Regex mode — an experimental mode that uses a user-supplied regular expression, similar to the aforementioned mask mode, to create candidates
• Mode stacking — utilises the mask or regex modes in combination with another mode

{{Portal|Free and open-source software}}

• Brute-force search
• Brute-force attack
• Crack (password software)

{{Reflist}}

• {{Official website}}

{{Password Cracking Software}}

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