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Mark D. Spivey

"Practical Hacking Techniques and Countermeasures"


For example you can crack only some salts using
???-salts:2??? faster, and then crack the rest using ???-salts:-2.???
Total cracking time will be about the same, but you will
get some passwords cracked earlier.
-format:NAME force ciphertext format NAME Allows you
to override the ciphertext format detection. Currently,
valid format names are DES, BSDI, MD5, BF, AFS, LM.
You can use this option when cracking or with ???-test.???
Note that John cannot crack password files with
different ciphertext formats at the same time.
-savemem:LEVEL enable memory saving, at LEVEL 1..3 You
might need this option if you do not have enough
memory, or do not want John to affect other processes
too much. Level 1 tells John not to waste memory on
login names, so you will not see them while cracking.
Higher levels have a performance impact: you should
probably avoid using them unless John does not work
or gets into swap otherwise.
Additional utilities:
There are some utilities in John??™s run directory:
unshadow PASSWORD-FILE SHADOW-FILE Combines
the password and shadow files (when you already have
access to both) for use with John. You might need this
because if you only used your shadow file, the GECOS
information would not be used by the ???single crack???
mode, and also you would not be able to use the -shells
option. You will usually want to redirect the output of
unshadow to a file.
unafs DATABASE-FILE CELL-NAME Gets password hashes
out of the binary AFS database, and produces a file usable
by John (again, you should redirect the output yourself).


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