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Comment: Re:Negative (Score 1) 545

by mseeger (#48141649) Attached to: Password Security: Why the Horse Battery Staple Is Not Correct

If you choose 4 English, non-trivial words, you already have about 40bit of entropy. Searching only 1% of the namespace would take Trillions of tries.

To have those tries, the provider (not the user) must have already screwed up. The user cannot defend against screwups of the provider of the password protected service efficiently

"Hard to guess" is aimed at direct, human guessing. If I know you love "Sarah", so "Sarah4me" makes a bad password. That would be your screwup.

My primary goal is: burden the user only what naturally belongs in his domain. Trying to offload your security as a company to the users (e.g. to reduce costs) usually backfire.

Comment: Negative (Score 5, Insightful) 545

by mseeger (#48134255) Attached to: Password Security: Why the Horse Battery Staple Is Not Correct

Good, bad & ugly - Your password

PASSWORD REQUIREMENTS

A good password must have two properties:

1) It has been memorized by the user
2) It is difficult to guess for a third person (even if he/she knows the user well)

But in most cases another requirement is thrown into the mix:

3) The password shell be complex (have a high entropy)
Usually the requirements take the form of a password policy like this:

The password must be at least 8 characters long
The password must contain upper- and lower-case letters
The password must contain a number
The password must contain a non-alphanumeric character

You notice anything? Yep, this policy only focuses on the third requirement. And it does so at the expense of the first requirement and (knowing human psychology) it also has a negative impact on the second requirement.

THREATS TO PASSWORDS

Let us take look at how the security of password can be compromised:

- The input of the password has been observed (by eavesdropping, key-loggers or by the ordinary Mark 1 Eyeball)

- The password has been re-used by the user in a different context where the attacker has access to it

- The attacker gained access to the encrypted storage of password and managed to extract it from there

- The password has been guessed by the attacker

How does having a complex password help you against these attacks?

In case of an attacker observing the user entering the password, no complexity will help. Rather the contrary, a password with mixed upper/lower-case, numbers and special characters is entered at a significantly slower pace. This helps an attacker observing the password by good old-fashioned peeking.

If the password is known to the attacker from the use in a different context, the complexity is no help either. Knowing the psychological side, cryptic passwords are rather compound the problem. Once a user has found a password that fits the typical policy, he tends to use it wherever such a password policy is in place and therefor increases the chances of an attacker to use a known password of the user in a different context.

In case of access to the encrypted password store, the complexity clearly helps to hamper the attacker (if the password is encrypted properly).

One would expect that password policy should help making a password un-guessable for a third person. From my personal observation the contrary is true. Under the watchful eye of a password policy they tend to stick to first names, upper-casing the first or last letter, replacing characters by similar looking special characters or numbers and/or adding numbers at the end (like birthdays).

Summary: Only in one attack scenario choosing a complex password helps, in all other scenarios it does not have any or even a negative impact. So let us look at this scenario a bit more detailed.

DECRYPTING PASSWORDS

To decrypt the password of a user, the attacker has first to have access to the password storage. At which point the first and most critical security failure has already occurred. And the user had nothing to do with it.

When it comes to decrypting a password, the algorithm used is a more important than the complexity of the password. If the service provider has not done his home work, complex passwords offer only little protection. This is another critical point, where the user has no influence whatsoever.

But in case of the service provider having botched the safety of his password file but made everything correct when choosing the algorithm the complexity of the user passwords can offer extra protection against the attacker.

Does this case justify all the negative impact?

I want to point out, that the safety of the encrypted password is not the responsibility of the user. So would say: Don't make him part of the process here. Don't shift the responsibility to to him where the service provider is responsible.

Remark: I did not specifically address the issue of an attacker trying out all passwords by automatically entering them one after another. It falls into the same category since it starts with a critical error on the service provider side by allowing this.

WHAT SHELL WE TEACH USERS ABOUT PASSWORDS?

I think we should focus on the first two requirements i started this comment with:

Choose a password you can remember

Use a password someone else does not associate with you
and (which is more important than complexity):

Use distinct passwords, at least for the most critical uses (Work, Banking, Apple, Facebook, Google, Paypal, Amazon) and never use those somewhere else.

If the user follows those three advice only, his security would be greatly improved. It is much better to use several (cryptographically) weak passwords than one good one for everything.

WHAT ABOUT PASSWORD COMPLEXITY?

I am not opposed to complex passwords, as long as it has no negative impact on the more important issues. There is nothing bad about advising the user about his password being weak or strong as information.

But if you do so, please do it right. Do not just look for which kind of characters are used. Don't care about the source of entropy as long at it is there.

"Test1234!" is not safer then "mucho danke shopping magazzini", rather the opposite. Let the user find his way to create a memorable complex password. If you force him into a scheme you think best, you will weaken passwords.

And: Except for the most critical uses, 40 bits of entropy are enough. If it is not enough, you need to rethink the way you store your passwords.

That is why i think XKCD has it right, no matter what Bruce Schneier says (i never thought i would agree on a security topic rather with a comic author than one of my most respected security experts).

ARE THERE EXCEPTIONS?

Yes, of course. There are always exceptions. But in those cases you should rather look into using two factor authentication than trying to get the users brain work in a way that evolution did not intend it to.

Comment: Too much (Score 1) 287

by mseeger (#47943351) Attached to: Slashdot Asks: What's In Your Home Datacenter?

Pure datacenter are: 2 firewalls, 1 Sun X2100, 1 QNAP NAS, 1 PC, 1 Raspberry, 1 VoIP-Gateway, 1 Homematic automation server, WLAN Controller
In the network: 5 mobile devices, 2 PC, 1 Notebook, BluRay-Player, 4 Audio Devices (Sonos), 2 Access Points, 2 USB-via-IP extender, Printer, Scanner, multiple IP-based sensors

Comment: Disagree (Score 1) 288

by mseeger (#46917049) Attached to: Applying Pavlovian Psychology to Password Management

Is the duty for password complexity correctly placed on the users shoulder? I think not...

The users has two jobs:

1. Select a password he can remember
2. Choosing a password someone else does not associate with him

Raising password complexity requirements makes those two jobs harder. In my observation, with rising password complexity, the users tend to re-use passwords more often (which is more detrimental to security than a less complex password).

For password complexity to matter, the service provider must have failed (lost the data) and succeeded (choosen a half-way decent algorithm) at the same time.

Therefor i consider the burden of password complexity wrongly plaxced at the users end.

Comment: Better than the Nest Protect? (Score 1) 167

I hope the Nest Thermostat is better than the Nest Protect Smoke Detector. Those gave me a case of serious "early adopter burn".

The Nest Protect detectors have the tendency to generate false alarms in clean air (no smoke, no dust, no steam) and are very hard to disable (get a ladder, dismount, get a screw driver, open device, remove battery). The idea of disabling a false alarm by WIFI has not occurred to them yet :-(.

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