this post was submitted on 23 Aug 2023
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Programming
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Yes its bad programing. These restrictions suggest that the company is either doing improper storage and processing, or does not understand how to deal with passwords.
The proper password storage is a hash. This is a cryptographic function that is easy to do and imbossible to undo. The hash function operates on the underlying binary representation of your password, and doesn't card what letters or symbols are in it. A program should take your password, hash it, and compare the result to the hash they have in their detebase.
The current recomended hash algorythm is called 'bcrypt'. Depending on the implementation, the input is between 50 and 70 bytes (the spec was a little unclear so people defined the inputs diferently, but the algorithe is the same). This means a password should be able to take at least 50 normal keyboard characters, including letters, symbols, and spaces. Anything less than that indicates a poor practice on behalf of the website.
(a lot of this is simplified. There is some variation and nuance that I don't think affects the main idea)
Well we don't know how that website is actually storing the password. They may well be using a password hash. Also, you should use scrypt or argon over bcrypt IMO. And there should be no upper restrictions on password length. argon2 can handle hashing megabytes of data in about the same time as a short password, so there's never a need to limit the password length.
What about Argon2id? What are the advantages of bcrypt?
I don't really know the strong points of either, I'm not a cryptographer. Bcrypt gets recommended because its relatively fast, its decent, and most importantly its already in most environments
Bcrypt is slow on purpose; all these methods are. More importantly, though, bcrypt is very well studied. Scrypt and argon2 had to catch up, but should be fine at this point.
Argon2 is the best (secure) crypto currently.
That said, adoption is slow, Bitwarden only recently implemented it for example.
That said, due to Argon2 being security-oriented, the recommended settings for it are pretty heavy.