Linux Commands Examples

A great documentation place for Linux commands


APG Bloom filter management program

see also : apg


apgbfm -f filter -n numofwords [-q] [-s]
apgbfm -f
filter -d dictfile [-q] [-s]
apgbfm -f
filter -a word [-q]
apgbfm -f
filter -A dictfile [-q]
apgbfm -f
filter -c word [-q]
apgbfm -f
filter -C dictfile [-q]
apgbfm -i
[-v] [-h]

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apgbfm is used to manage Bloom filter that is used to restrict password generation in APG pasword generation software. Usage of the Bloom filter allows to speed up password check for large dictionaries and has some other benefits.

The idea to use Bloom filter for that purpose is came from the description of the OPUS project OPUS: Preventing Weak Password Choices Purdue Technical Report CSD-TR 92-028 writen by Eugene H. Spafford.

You can obtain this article from:

It has very nice description of Bloom filter and it’s advantages for password checking systems.

In simple words, apgbfm generates n hash values for every word and sets corresponding bits in filter file to 1. To check the word apgbfm generates the same hash functions for that word and if all n corresponding bits in filter file are set to 1 then it suppose that word exists in dicionary. apgbfm uses SHA-1 as a hash function.

apgbfm can be used as standalone utility, not only with apg, or apgd.

Filter file format can be changed in the future. I’ll try to make file formats compatible but i can not guaranty this.


apgbfm may slow down your computer during filter creation.


-f filter

use filter as the name for Bloom filter filename.

-i filter

print information about filter.

-n numofwords

create new empty filter for numofwords number of words. Useful when you want to fill filter dynamicaly.

-d dictfile

create new filter from dictfile. It may take a lot of time to generate filter from a big dictionary. In that dictionary you may place words (one per line) that should not appear as generated passwords. For example: user names common words, etc. You even can use one of the dictionaries that come with dictionary password crackers. This check is case sensitive. For example, if you want to reject word ’root’, you should insert in dictfile words: root, Root, RoOt, ... , ROOT. To indicate that program is working apgbfm prints dot for every 100 words added in dictionary.

-a word

add word to the filter.

-A dictfile

add all words from dictfile to the filter. To indicate that program is working apgbfm prints dot for every 100 words added in dictionary.

-c word

check word for appearance in the filter.

-C dictfile

check every word from dictfile for appearance in the filter.


quiet mode.


create new filter in case-insensitive mode.


print version information.


print help information.

exit code

On successful completion of its task, apgbfm will complete with exit code 0. An exit code of -1 indicates an error occurred. Textual errors are written to the standard error stream.




None. If you’ve found one, please send bug description to the author.

This man page is Alpha too.

see also



Adel I. Mirzazhanov, <a-del[:at:]iname[:dot:]com>
Project home page:

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