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0 pointsnwh12y ago0 comments

I'm very much aware of that. I'm saying that because they're disallowing the submission of spaces, they aren't hashing their passwords when they get to the server.

> they're checking the string server-side, before hashing and storing the hash to their persistent data store.

But why? People don't just add a rule because they feel like it, I'm suggesting that they are storing it in a stupid way that is not hashed and does not allow spaces.

> part of me would like to guess that the reason spaces might be forbidden in passwords (and pass phrases) would be to prevent frequency analysis.

The output of a cryptographic hash is completely random, you can't do any sort of analysis except for determining H(a) == H(b). You don't even know if H(b) was the same input as H(a) or just a collision against it.

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4 comments · 1 top-level

arcticPeril12y ago· 3 in thread

  > But why?

Because you cannot trust any checks performed on the client-side, since the user may have total control over the client-side system, and possess the ability to (somehow) bypass or spoof client-side validation.

Client-side validation only exists to pluck the low-hanging fruit, and provide convenience to the majority of users. You cannot rely on any client-side events, when attempting to secure server-side resources.

All user input must be considered evil until proven otherwise.

nwhOP12y ago

You've utterly missed the point of this.

If they hashed the user input, it wouldn't matter what the client gave them in terms of password requirements. Spaces, special characters, arbitrary lengths up to tens of thousands of characters would all be fine with a cryptographic hash, there's no way the resulting hash would be anything but a fixed length of n bytes. Nothing "evil" can make it through being hashed.

The password requirements Flickr has set show that they are not using a cryptographic hash, the limitations on length and character set imply that they are being stored incorrectly, either in plain text or a space delimited format. There's no reason to have these limitations if this were not the case.

arcticPeril12y ago

So you're just going to implicitly trust the user's browser to generate the hash for you? Good luck with that, sir.

And there is a reason to limit length, the very obvious reason being that short passwords are easier to brute force.

Reduced character sets (numeric only, for example) are also easier to brute force, so by forbidding spaces, technically, they've reduced the character set of their passwords by at least one character (not that it's of any particular concern, all things considered).

By the way, I made mention that perhaps they're encrypting the string, and not hashing it. Did you miss that part?

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gaadd3312y ago

I don't see how setting business rules means that they aren't using a cryptographic hash. Can you explain why that has to be true?

Perhaps eliminating a frequently made mistake by people who don't have much computer expertise is the reason. Wouldn't it be possible that they have found that a large number of support requests for newly created accounts are due to people accidentally adding spaces? So by eliminating spaces, they can still hash the contents without a problem however they also reduce the support load and increase the usability by a subset of their users.

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