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Comments on Are "strong passwords" at all meaningful?
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Are "strong passwords" at all meaningful?
Whenever registering to diverse sites on the net, you are often forced to enter a so called "strong password", which would ideally contain both upper case letters, lower case letters, digits, and some other character like punctuation. As hard to remember as possible.
What I don't understand from a software development point of view is how these characters would make that much of a difference.
All of it seems to assume that a hacker trying to break a password would utilize so-called brute force. That is: try "A", try "B" ... "try AA" and so on. The more variations, the longer it takes to execute the brute force algorithm.
If I have a password of up to 10 capital letters A to Z plus "empty", that's 27 combinations, for a total of 2710 combinations.
As opposed to having a 10 letter password in the whole UTF8/ASCII 7 bit range, 127 combinations - 32 non-printable + 1 empty = 96, for a total of 9610 combinations.
Sure, a significant difference, astronomical even. But... if they would execute a brute force across TCP/IP they can maybe try one combination every millisecond or something, assuming great bandwidth. Worst case scenario for the 2710 scenario is then 57 days. Some 4 weeks on average. Assuming there's no big latency or packet drop for a significant lower bandwidth, in which case this isn't really feasible at all.
I don't see anyone setting up a brute force operation for that in order to access John Doe's Gmail account or whatever... it is already too much of an obstacle. Unless they hope to get lucky on the initial bunch permutations, which can of course happen.
Assuming that brute force is actually what's used, which sounds quite unlikely to me. Instead of something else entirely: keyword logging, packet sniffing, the human factor ("Hi this is your bank please send us your password") etc etc.
So is the usefulness of this whole "strong password" thing just an urban legend, where companies force us to memorize ridiculously hard to remember passwords for no real gain? Why is the number of symbol table combinations in the password oh so important on almost any Internet site these days?
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Disclaimer: I am not a security expert nor a security professional.
There is, of course, a relevant XKCD comic for this:
The entropy numbers appear to be accurate based on this security.stackexchange post. It actually assumes a dictionary attack, which involves checking for common words in passwords and is sometimes used to discredit the "correcthorsebatterystaple" method of password generation. However, when password checkers are looking at password strength, they usually are comparing passwords of equal lengths. An 8 character password with only alphabetic characters will be weaker than an 8 character password with digits, special symbols, and alphabetic characters. If you assume that people will use the shortest password they can get away with, then forcing them to include more variety makes sense. It also allows the site to use less database storage space while forcing better passwords than just 8 alphabetic characters.
In my personal experience, security professionals assume people will use some kind of password storage program. They don't seem to consider the difficulty of remembering the sheer number of passwords required for various necessary accounts. None of the various security seminars I have participated in for work offered any solutions. Password requirements are based on site security for that site alone; they don't take into account how users are supposed to handle 50 sites with difficult to remember passwords.
To answer your question about attacks per second: attackers aren't necessarily trying to attack over the internet. They will use copies of databases full of hashed passwords and run hundreds of attacks per second on them. Once they have a plaintext password, they can try that on other sites such as banks (people reuse passwords enough for this to be worth it). So the password strength really can matter, especially if you reuse passwords.
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