We all know why password reuse is bad: eventually some site at which you have an account that did not properly hash+salt user passwords will get hacked, and your password will be published in a big dump. Then some hackers will take that user/pass combination and try it on every site they think that can get something useful from.
I know that password managers are the recommended solution to having a unique totally random password for every site. But they are not completely without their own difficulties, and especially trying to persuade non-technical people to use them may be difficult. Instead, as a minimal alternative to shared passwords, one might have a simple algorithm to generate unique passwords from a shared random component. A minimal example might be
<sitename>_<good random password>. So my passwords might be
etc, where the second part is shared. Now, any idiot actually trying to hack me specifically could probably guess my algorithm even knowing only one password, and trivially if they got ahold of two, so if I were for some reason a high-profile target this would be a bad plan. But if anyone wanted to hack me, I'm probably in trouble no matter what I do. Assuming I'm not a high profile target, it seems to me a simple algorithm like this would protect me from the majority of password-reuse dangers, because no human will ever see my password specifically.
So really I'm asking, is this reasoning flawed? Is this kind of algorithmically-generated password actually any safer than exact password reuse? Or are password dumps used differently than I have in mind? The accepted answer to this question suggests that varied passwords are only useful if it is hashed, but to me it seems that a hacker having the cleartext password doesn't help them.
I agree this is fundamentally security-by-obscurity, but maybe security-by-anonymity would be a better title. My password would be one of a million in a big dump, with essentially zero chance that any human would ever actually see mine.
the question (edited to be more explicit):
- An average person (not a high profile target for hackers) uses an algorithm to generate unique site passwords.
- The algorithm is extremely simple, so that a human could guess the algorithm given even a single password
- One or more of those passwords have been obtained by hackers
Is this person any less likely to be hacked on other sites than a person who uses the same password on every site? If not, is it because
- There is a reasonable chance that a human will actually look at this password?
- Attackers already look for some kinds of algorithmically-generated passwords?
- Some other reason?
Many have pointed out that using a password manager is a better idea. In particular ThoriumBR and others point out that this scheme is unsustainable, because once I need to change one of the passwords, I now have to change my algorithm.
These are very good points, but not what I am hoping to learn from this question.