Isn't a password a form of security through ob

问题:

I know that security through obscurity is frowned upon and considered not really secure, but isn't a password security through obscurity? It's only secure so long as no one finds it.

Is it just a matter of the level of obscurity? (i.e. a good password well salted and hashed is impractical to break)

Note I'm not asking about the process of saving passwords (Assume they are properly hashed and salted). I'm asking about the whole idea using a password, which is a piece of information, which if known could compromise a person's account.

Or am I misunderstanding what security through obscurity means? I guess that's what I assume it to mean, that is there exists some information which if known would compromise a system (in this case, the system being defined as whatever the password is meant to protect)

回答1:

You are right in that a password is only secure if it is obscure. But the "obsure" part of "security through obscurity" refers to obscurity of the system. With passwords, the system is completely open -- you know the exact method that is used to unlock it, but the key, which is not part of the system, is the unknown.

If we were to generalize, then yes, all security is by means of obscurity. However, the phrase "security through obscurity" does not refer to this.

回答2:

Maybe it's easier to understand what Security-by-Obscurity is about, by looking at something that is in some sense the opposite: Auguste Kerckhoffs's Second Principle (now simply known usually as Kerckhoffs's Principle), formulated in 1883 in two articles on La Cryptographie Militaire:

[The cipher] must not be required to be secret, and it must be able to fall into the hands of the enemy without inconvenience.

Claude Shannon reformulated it as:

The enemy knows the system.

And Eric Raymond as:

Any security software design that doesn't assume the enemy possesses the source code is already untrustworthy.

An alternative formulation of that principle is that

The security of the system must depend only of the secrecy of the key, not the secrecy of the system.

So, we can simply define Security-by-Obscurity to be any system that does not follow that principle, and thus we cleverly out-defined the password :-)

There are two basic reasons why this Principle makes sense:

1. Keys tend to be much smaller than systems, therefore they are easier to protect.
2. Compromising the secrecy of a key only compromises the secrecy of all communications protected by that key, compromising the secrecy of the system compromises all communications.

Note that it doesn't say anywhere that you can't keep your system secret. It just says you shouldn't depend on it. You may use Security-by-Obscurity as an additional line of defense, you just shouldn't assume that it actually works.

In general, however, cryptography is hard, and cryptographic systems are complex, therefore you pretty much need to publish it, to get as many eyeballs on it as possible. There are only very few organizations on this planet that actually have the necessary smart people to design cryptographic systems in secrecy: in the past, when mathematicians were patriots and governments were rich, those were the NSA and the KGB, right now it's IBM and a couple of years from now it's gonna be the Chinese Secret Service and international crime syndicates.

回答3:

No. Let's look a definition of security through obscurity from wikipedia

a pejorative referring to a principle in security engineering, which attempts to use secrecy (of design, implementation, etc.) to provide security.

The phrase refers to the code itself, or the design of a system. Passwords on the other hand are something a user has to identify themselves with. It's a type of authentication token, not a code implementation.

回答4:

I know that security through obscurity is frowned upon and considered not really secure, but isn't a password security through obscurity? It's only secure so long as no one finds it.

In order to answer this question, we really need to consider why "security through obscurity" is considered to be flawed.

The big reason that security through obscurity is flawed is that it's actually really easy to reverse-engineer a system based on its interactions with the outside world. If your computer system is sitting somewhere, happily authenticating users, I can just watch what packets it sends, watching for patterns, and figure out how it works. And then it's straightforward to attack it.

In contrast, if you're using a proper open cryptographic protocol, no amount of wire-sniffing will let me steal the password.

That's basically why obscuring a system is flawed, but obscuring key material (assuming a secure system) is not. Security through obscurity will never in and of itself secure a flawed system, and the only way to know your system isn't flawed is to have it vetted publicly.

回答5:

Passwords are a form of authentication. They are meant to identify that you are interacting with who you are supposed to interact with.

Here is a nice model of the different aspects of security (I had to memorize this in my security course)

http://en.wikipedia.org/wiki/File:Mccumber.jpg

Passwords are an aspect of the confidentiality aspect of security.

While probably the weaker of the forms of authentication (something you know, something you have, something you are), I would still say that it does not constitute security through obscurity. With a password, you are not trying to mask a facet of the system to try to keep it hidden.

Edit:

If you follow the reasoning that passwords are also a means of "security Throguh Obscurity" to it's logical end then All security, including things like encryption, is security through obscurity. Then that means, the only system that is not secured through obscurity is one that is surrounded in concrete and sunk to the ocean floor, no one ever being allowed to use it. This reasoning, however, is not conducive to getting anything done. Therefore we use Security Through obscurity to describe practices that use not understanding the implementation of a system as a means of security. With passwords, the implementation is known.

回答6:

No, they are not.

Security through obscurity means that the process that provides the access protection is only secure because its exact details are not publicly available.

Publicly available here means that all the details of the process are known to everyone, except, of course, a randomized portion that constitutes the key. Note that the range from which keys can be chosen is still known to everyone.

The effect of this is that it can be proven that the only part that needs to be secret is the password itself, and not other parts of the process. Or conversely, that the only way to gain access to the system is by somehow getting at the key.

In a system that relies on the obscurity of its details, you cannot have such an assurance. It might well be that anyone who finds out what algorithm you are using can find a back door into it (i.e. a way to access the system without the password).

回答7:

The short answer is no. Passwords by themselves are not security by obscurity.

A password can be thought of as analogous to the key in cryptography. If you have the key you can decode the message. If you do not have the key you can not. Similarly, if you have the right password you can authenticate. If you do not, you can not.

The obscurity part in security by obscurity refers to how the scheme is implemented. For example, if passwords were stored somewhere in the clear and their precise location was kept a secret that would be security by obscurity. Let's say I'm designing the password system for a new OS and I put the password file in /etc/guy/magical_location and name it "cooking.txt" where anyone could access it and read all the passwords if they knew where it was. Someone will eventually figure out (e.g. by reverse engineering) that the passwords are there and then all the OS installations in the world will be broken because I relied on obscurity for security.

Another example is if the passwords are stored where everyone can access them but encrypted with a "secret" key. Anyone who has access to the key could get at the passwords. That would also be security by obscurity.

The "obscurity" refers to some part of the algorithm or scheme that is kept secret where if it was public knowledge the scheme could be compromised. It does not refer to needing a key or a password.

回答8:

Yes, you are correct and it is a very important realisation you are having.

Too many people say "security through obscurity" without having any idea of what they mean. You are correct in all that matters is the level of "complexity" of decoding any given implementation. Usernames and passwords are just a complex realisation of it, as they greatly increase the amount of information required to gain access.

One important thing to keep in mind in any security analysis is the threat model: Who are you worried about, why, and how are you preventing them? What aren't you covering? etc. Keep up the analytical and critical thinking; it will serve you well.