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What technical reasons are there to have low maximum password lengths?

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Re: What technical reasons are there to have low maximum password lengths?

#11

It's amazing how all the comments so far have entirely missed that it's the top answer that was really submitted, not the question.

I think it may be a problem with the link itself. In the past I've seen SO links that auto scroll to the answer of interest, however this one just loaded to the top of the page.

Re: What technical reasons are there to have low maximum password lengths?

#13

It's amazing how all the comments so far have entirely missed that it's the top answer that was really submitted, not the question.

"The Internet is full of chimpanzees."

I am reminded of Egor Homakov and his various exploits, especially in the Rails community. Someone points out a problem and the community collectively decided to ignore him.

Re: What technical reasons are there to have low maximum password lengths?

#14
My bank limits my password to 8. When I questioned while creating my account, they asked me to visit the login page - in the login page you are asked for the answer of the security question and also presented with 8 input boxes - one for each of of the password characters - but having to enter only randomly selected few from the password ( for preventing key loggers from getting password, of course ). This seemed like a valid technical reason to limit passwords to 8.

Re: What technical reasons are there to have low maximum password lengths?

#15

"Because it's hard enought remember 12 characters already" -my bank's tech support

This could be translated to,

"Because we estimate the added costs of supporting users will increase by X due to more users forgetting their password due to length"

Re: What technical reasons are there to have low maximum password lengths?

#16

There's one reason I haven't seen mentioned yet: Because the developer is storing passwords in plaintext, and he wants to save database space. Now, this is not a good reason, but it is a reason nevertheless. Please note that you should never, ever, ever, ever store passwords in plaintext.

Because the developer is storing passwords in plaintext, and he wants to save database space.

This seem far fetched, not sure what thought process would lead anyone to come to this conclusion. Even if you have a million users, you have ~8MB worth of passwords. I'd imagine even developers who are not competent in cryptography realise that.

Re: What technical reasons are there to have low maximum password lengths?

#17

"Because it's hard enought remember 12 characters already" -my bank's tech support

Typically bank tech support have no idea about the inner workings of their website.

My bank uses 2 stage auth to login which works really well. However, they have a sort of shortcut service where you can activate and pick a password and then use that password to do quick stuff online or in their mobile app. The quick stuff still let's you transfer away all your money to someone else so it's basically a gaping hole.

That password has the wildest restrictions I've seen. It allows only a-zA-Z0-9 and it must consist of exactly 6 characters. No restriction on containing at least one digit or anything like that.

I've e-mailed them several times about this but their response is that this particular service has been out sourced to one of the many companies they out source things to, so they have no control at all over it.

And it's rather funny because you can tell that when you use this service, you're taken to a completely different server farm than the rest of the internet site. Fucking scary is what I call it.

Re: What technical reasons are there to have low maximum password lengths?

#18

My bank limits my password to 8. When I questioned while creating my account, they asked me to visit the login page - in the login page you are asked for the answer of the security question and also presented with 8 input boxes - one for each of of the password characters - but having to enter only randomly selected few from the password ( for preventing key loggers from getting password, of course ). This seemed lik…

May I ask what bank you bank with?

Re: What technical reasons are there to have low maximum password lengths?

#19

There's one reason I haven't seen mentioned yet: Because the developer is storing passwords in plaintext, and he wants to save database space. Now, this is not a good reason, but it is a reason nevertheless. Please note that you should never, ever, ever, ever store passwords in plaintext.

Because the developer is storing passwords in plaintext, and he wants to save database space. This seem far fetched, not sure what thought process would lead anyone to come to this conclusion. Even if you have a million users, you have ~8MB worth of passwords. I'd imagine even developers who are not competent in cryptography realise that.

Some developers love that kind of micro optimizations. Even smart ones. I've had my varchar(256) columns changed to a more modest varchar(30) because I was "wasting space." Those people dont like being wrong either so there's no point arguing it either and instead concentrate on the bigger issues.

Re: What technical reasons are there to have low maximum password lengths?

#20

There's one reason I haven't seen mentioned yet: Because the developer is storing passwords in plaintext, and he wants to save database space. Now, this is not a good reason, but it is a reason nevertheless. Please note that you should never, ever, ever, ever store passwords in plaintext.

Because the developer is storing passwords in plaintext, and he wants to save database space. This seem far fetched, not sure what thought process would lead anyone to come to this conclusion. Even if you have a million users, you have ~8MB worth of passwords. I'd imagine even developers who are not competent in cryptography realise that.

If you allow truly unlimited-length passwords, malicious users can set gigabyte-long passwords. Whether you hash them or just store them, that's a DoS waiting to happen with every login.

So, there actually is a reasonable limit for the length of passwords, email addresses, and most other user-editable fields that end up either being hashed, or shoved through to the database. That limit is just probably somewhere around 100KB to 1MB, not "eight". ;)

More importantly, that limit is an infrastructure concern, not a business-domain concern; it's best enforced by something like nginx spitting out a 400, not the model-validation logic in your app server.

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