this post was submitted on 20 Aug 2024
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I agree but I think the problem is that some apps/sites have strict password requirements, which usually includes adding upper-case, symbols, numbers, and then limits the length even sometimes...
At my previous bank the password had to be a 5 digit PIN code...
At one point, Charles Schwab allowed a password of infinite length, but SILENTLY TRUNCATED ALL PASSWORDS TO 8 DIGITS.
This is something I sent a few angry emails about wherever I could find an opportunity.
Sketchy indeed. I've seen this as well, and the redeeming thing about it is that you're locked out after 3 unsuccessful login attempts - so no matter how easy bruteforcing would be, there's a safety catch dealing with it.
Which is funny because those strict rules reduce the number of combinations an attacker has to guess from, thereby reducing security.
Provably false. That's only true if the rules specify some really wacky requirements which I haven't seen anywhere except in that one game about making a password.
Think about it this way. If you have a password of maximum length two which only accepts lowercase letters, you have 26 choices for the first character & 26 for the next. Each of the 26 characters in the first spot can be combined with any of the 26 characters in the second spot, so 26 * 26 = 676 possible passwords.
By adding uppercase letters (for a total of 52 characters to choose from), you get 52 * 52 = 2704 possible passwords. It increases significantly if you increase the length beyond two or can have more than just upper & lowercase letters.
Computers have gotten so efficient at generating & validating passwords that you can try tens of thousands of passwords in a minute, exhausting every possible two-letter password in seconds starting with
aaand ending withZZ.The only way you would decrease the number of possible passwords is if you specified that the character in a particular spot had to be uppercase, but I've never seen a password picker say "your fourth character must be a lowercase letter".
You don't add them, you enforce at least one. That eliminates all combinations without upper case letters.
So, without this rule you would indeed have the 52x52 possible passwords, but with it you have (52x52)-(26x26) possible passwords (the second bracket is all combinations of 2 lowercase letters), which is obviously less.
Wrong. In your example, for any given try, if you have put a lowercase letter in spot 1, you don't need to try any lowercase in spot 2.
Any information you give the attacker eliminates possible combinations.
I think I'm confused on your point.
I interpreted your statement to mean "adding a requirement for certain types of characters will decrease the number of possible passwords compared to no requirements at all", which is false. Even in your example above, with only two letters, no numbers / special characters allowed, requiring a capital letter decreases the possibilities back to the original 676 possible passwords - not less.
Perhaps you're trying to say that passwords should all require certain complexity, but without broadcasting the password requirements publicly? I suppose that's a valid point, but I don't think the tradeoff of time required to make that secure is worth the literal .000001% (I think I did the math right) improvement in security.
No it doesn't. It reduces the possibilities to less than the 52x52 possibilities that would exist if you allowed all possible combinations of upper and lower case letters.
You are confused because you only see the two options of enforcing or not allowing certain characters. All characters need to be allowed but none should be enforced. That maximizes the number of possible combinations.
No, because that's still the same. An attacker can find out the rules by creating accounts and testing.