Pwnhub Presents Password Cracking – John The Ripper | Cracking Modes
John The Ripper Cracking Modes
John has a number of different password hash cracking modes. These various modes can be used to crack password hashes in different ways. If one method of cracking a password hash didn’t work, then you could try a different mode.
By far the most common mode I’ve used is the wordlist mode. This mode requires the user to specify a wordlist. This wordlist could be bespoke and created by tools like Crunch. Or it could be one of the many wordlists available on the internet. John will then go through the list line by line attempting to match the hash to the word. This mode also offers a mangle option where it will apply rules to the word. In short, the word password could be automatically mangled to something like P@55W0RD.
Single Crack Mode
As stated on the Openwall (John Developers) website, the single crack mode is the cracking mode you should start with. It will use login names, full names, and user home directory names as candidate passwords. It will then apply a large set of mangling rules. Successfully cracked passwords will also be tried against any other hashes that have been loaded. In theory, this mode should be able to crack a list of password hashes faster than if you were to supply the hashes separately.
This mode will try all possible character combinations. This is a powerful mode but would likely take longer than using a wordlist. If it tries all possible character combinations then it would eventually guess the correct password. If you know the length of the password then you can specify it to make cracking quicker. However, if you don’t know the length of the password and the password is a fairly long and complex one, then you could be waiting a while… like forever.
From what I’ve read and what I understand, I believe this mode requires you to create your own cracking mode. The program code is a subset of C and would be compiled by John at startup. This could be useful if the hashing algorithm used to create the hash is bespoke. You could then write your own cracking module and load it into john to crack those custom-created hashes.