![]() In fact, since the -r switch can be used to exclude any arbitrary character, this could be used to effect on other non-special characters as well, but that is not within the scope of the original question. This command will return one ( -1 - see note) ten-character ( 10) secure ( -s) password that includes symbols ( -y), numbers ( -n), and capitals ( -c), with the set of symbols being restricted ( -r) to only those passed into the invert function. If you don't put it in single quotes, you may get unexpected and undesired results. Note here that the list of escaped special characters is in single quotes. If you specify the list of all special characters, you can pass your "opt-in" characters and programmatically return the opt-out list. Execute the following command to update the package lists: sudo apt update. This tutorial shows how to install pwgen on Ubuntu 20.04. This tool is designed for generating secure passwords which can be easily memorized by humans. ![]() Solution? Create your own inverse function. The pwgen is a tool that enables to generate random passwords via command line. The pwgen application may not have this functionality built in, but as you've already noted, we can use the -r switch to accomplish the inverse. But for most practical purposes, if you just be sure to generate things that are a few characters longer than you otherwise might, then your gain in strength from generating a longer password will surely overwhelm the loss of strength from their non-uniform behavior.I sympathize. It is frustrating that popular password generators are hard to actually analyze in terms of strength. So between the relatively small modulo bias and the much larger deliberate bias toward more likely sounding syllables, it would require a level of analysis beyond what I am willing to do to actually calculate the min-entropy. It is a relatively small bias that comes up through a common design error when trying to pick a number between 1 and N even when the underlying random number generator is good. I have argued that we should be using min-entropy in such cases.Īdditionally, some versions of pwgen are subject to the modulo bias. There is no clear answer to what notion of entropy is most appropriate when password creation schemes when the schemes do not produce uniform output. A link to the video of the talk and the slides are here: Note I discuss this in my PasswordConLV15 talk. This is true of most "pronounceable" password generators. This is because it tries to mimic some of the frequencies we have in English. Some passwords are more likely than others. Pwgen does not produce passwords uniformly. ![]() The actual answer to your question is too hard for me to reasonably calculate, but I can say a few useful things about this. But it is far more than enough against automatized login scripts particularly if something (like a fail2ban) causes a hard, low limit to the possible tries. It means, that pwgen is probably quite sophistically tuned also for the high entropy, and not only to produce easily pronouncable passwords.ģ6 bit is not enough defense against gpu-accelerated, clustered brute force attacks. Typically, text data can be compressed to around 10% of its original size, while xz could reach only a 60% ratio. Note: although the output was a text file, xz could compress it only with a surprisingly bad ratio. Replayed measurements didn't show a significant dispersion.īased on this, the entropy of a single, 8 byte-long pwgen password is 8*8*593412/1048576 = 36.2 bits of entropy. Generates an 1MB long password, compresses it with the best known flags of the best known compressor, and measures the size of the output. The command pwgen 1048576|xz -9ve -|wc -c But I think we can use a strong compressor to approximate the entropy. An exact answer would require a deeper analyzis of the pwgen source code, or a more exact measurement.
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