![]() ![]() 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. 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. Used interactively, pwgenwill display a screenful of passwords, allowing the user to pick This prevents someone from being able to 'shoulder surf' the user's chosen password. standard output is a tty device or a pipe to another program. Pwgen does not produce passwords uniformly. The pwgenprogram is designed to be used both interactively, and in shell scripts. 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. So for example pwgen -cnyB -r '' should do the trick. The command pwgen 1048576|xz -9ve -|wc -c kev To exclude the literal backslash character, you can try using the double backslash as the value for your option. But I think we can use a strong compressor to approximate the entropy. I believe that certain big brothers have computing power that can outdo us anyday, no matter how many hands you have.An exact answer would require a deeper analyzis of the pwgen source code, or a more exact measurement. (I hope I got that right.)Īnyway, from a practical point of view, I don't think it'll matter that much. How are you measuring entropy Each standard. Once the British heard of this through their intelligence channels, they knew that they could rule out the first ring's letter from the 2nd ring, and the 2nd ring's letter from the last ring (there being 3 rings each based on the alphabet). The outcome of a single coin toss - heads or tails - has one bit of entropy. The Nazi code guys believed that to have two of the same letters next to each other within the 3 character combination meant that their code wasn't random enough and would change/redo the random code for that day. I read that this thinking helped Bletchley Park crack the German's Enigma encrypts during WWII. If you are interested in this type of stuff. Not sure if I still have it, wrote it 5 years ago. Thought that would make it too easy, so now the program provides a little more spread while keeping some clusters. One thing I would like to throw out there is do people consider which hand is used to type the password? Because once the password generator spat out a password that required only my left hand. ![]()
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