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Flaws in deterministic password managers

tonyarcieri.com

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Re: Flaws in deterministic password managers

#51

Post by problems »

tomrod wrote: post #50
problems wrote: post #34

Earlier quoted context omitted.

Which is bad. I've reverse engineered script kiddie malware far too many times to find them shipping "iStealer" and similar, which basically just dump browser password stores and send them to a gmail or FTP account. Often these pieces of malware include the SMTP credentials to the same gmail account or FTP access to download the results. And having seen their results, let me just say, these script kiddies can do damn…

Neophyte to all this. What is a browser password store? Do you mean never letting Chrome (or whatever) save a password?

Yes. If you want to see how vulnerable you are to this sort of attack, Nirsoft ships a good tool called WebBrowserPassView:

http://www.nirsoft.net/utils/web_browser_password.html

Be aware, this may be detected as malware or a "hacking tool" by your AV for obvious reasons.

Re: Flaws in deterministic password managers

#52

Post by minitech »

I use a deterministic password generator so all I have to remember is my master password and default password scheme to get access to all my critical accounts (critical ones generally don’t have silly password requirements). If I were using something that stored passwords and lost my database somehow, I’d lose access to all of those.

Re: Flaws in deterministic password managers

#53

Post by pwinnski »

tomrod wrote: post #50
problems wrote: post #34

Earlier quoted context omitted.

Which is bad. I've reverse engineered script kiddie malware far too many times to find them shipping "iStealer" and similar, which basically just dump browser password stores and send them to a gmail or FTP account. Often these pieces of malware include the SMTP credentials to the same gmail account or FTP access to download the results. And having seen their results, let me just say, these script kiddies can do damn…

Neophyte to all this. What is a browser password store? Do you mean never letting Chrome (or whatever) save a password?

I never let my browsers store a password to anything, ever. I rely on 1Password to supply all passwords, and having my browser also store a password doubles the attack surface.

Re: Flaws in deterministic password managers

#54

Post by minitech »

Scaevolus wrote: post #46

Another flaw: deterministic password managers are inherently vulnerable to brute forcing-- it's basically like sending your password database to every site you log into. Ideally they use a very expensive KDF, but I've seen implementations that use weak derivations like 10,000 round PBKDF2.

Use a master password that’s impossible to brute-force, then. (128 bits.)

Re: Flaws in deterministic password managers

#55

Post by hackuser »

Retr0spectrum wrote: post #39

I have an irrational(?) fear of vault password managers. I see it as a single point of failure. Furthermore, the more "useful" they become, with browser extensions etc., the greater the attack surface becomes. Because of this fear, I generate random passwords and memorise them, which is not ideal.

> the more "useful" they become, with browser extensions etc., the greater the attack surface becomes

Also, the more popular the password manager becomes, the more valuable cracking it becomes. One exploit can yield the email, banking, workplace, confidential document, and other passwords for many millions of people. If you are an attacker, it would be worth it to have the exploit on file, proactively, for the next time you attack someone using that password manager.

Re: Flaws in deterministic password managers

#56

Post by minitech »

ythn wrote: post #10
tptacek wrote: post #6

Earlier quoted context omitted.

First, your proposed scheme relies on doubling words to get complexity without imposing too much of a tax on the user. But because passwords must be reasonable to type, that rule (and any rule like it --- I get that the "key" in this scheme is in part the weird rules you come up with) limits you to smaller words, which can very quickly be searched. Worse, an attacker who sees one of your passwords has a pretty decent…

> Worse, an attacker who sees one of your passwords has a pretty decent shot at brute forcing the rules you use, and an attacker who sees two of them has the rules and has totally cracked your scheme. If an attacker is specifically targeting me and thinking about my passwords, there's not much I can do at that point. Password security in general kind of relies on attackers scanning huge quantities of credentials and…

> If an attacker is specifically targeting me and thinking about my passwords, there's not much I can do at that point.

You could use a password manager…

Re: Flaws in deterministic password managers

#57

Post by rocqua »

theandrewbailey wrote: post #37
rocqua wrote: post #31

Earlier quoted context omitted.

That is massive overkill. 128 bits of security is way more than sufficient. 23 characters (uppercase, lowercase, numbers) already gives much security. Honestly, 128 bits is already overkill. An attacker that determined is probably quite proficient at rubber hose cryptography. The point of PW manager is to prevent compromise from spreading. Not to keep a motivated NSA out of your PC.

I know, but that's a good property to have, it's easy to do, and the extra costs are insignificant.

It's a useless property to have, and the extra costs make it much harder to transcribe by hand. Never mind the fact that using non-ascii is asking for compatibility problems.

Honestly, diceware[1] is probably an even better choice, though it sometimes fails symbol count requirements.

[1] http://world.std.com/~reinhold/diceware.html

Re: Flaws in deterministic password managers

#58

Post by Gee19 »

hackuser wrote: post #55
Retr0spectrum wrote: post #39

I have an irrational(?) fear of vault password managers. I see it as a single point of failure. Furthermore, the more "useful" they become, with browser extensions etc., the greater the attack surface becomes. Because of this fear, I generate random passwords and memorise them, which is not ideal.

> the more "useful" they become, with browser extensions etc., the greater the attack surface becomes Also, the more popular the password manager becomes, the more valuable cracking it becomes. One exploit can yield the email, banking, workplace, confidential document, and other passwords for many millions of people. If you are an attacker, it would be worth it to have the exploit on file, proactively, for the next t…

This is only true for cloud based password managers. I recommend using 1Password or KeePassX with Dropbox.

Re: Flaws in deterministic password managers

#59

Post by [deleted] »

tomrod wrote: post #50
problems wrote: post #34

Earlier quoted context omitted.

Which is bad. I've reverse engineered script kiddie malware far too many times to find them shipping "iStealer" and similar, which basically just dump browser password stores and send them to a gmail or FTP account. Often these pieces of malware include the SMTP credentials to the same gmail account or FTP access to download the results. And having seen their results, let me just say, these script kiddies can do damn…

Neophyte to all this. What is a browser password store? Do you mean never letting Chrome (or whatever) save a password?

[deleted]

Re: Flaws in deterministic password managers

#60

Post by clark800 »

pwinnski wrote: post #23
clark800 wrote: post #22

I've been surprised by how negative the opinions of deterministic password managers have been since I've been using one for over two years and it has been a much better experience overall than using KeePass on Dropbox, and I also think that it's more secure than cloud-based systems (see point 4). My take on the points in the post: 1. Out of the 100 or so sites that I use, only a few have password policies that requir…

If your browser is caching all of your passwords, I think you've got security problems well outside the scope of your choice of password managers.

Only the override parameters for a site are cached, such as a boolean to indicate that symbols are disabled or an integer reset counter. The passwords are never cached.
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