HashMask - Another (More Secure) Experiment in Password Masking • Hacker News Board

Re: HashMask - Another (More Secure) Experiment in Password Masking

#21

Post by tptacek » Thu, Jul 09, 2009, 10:41 PM UTC

umbrae wrote: post #19

tptacek wrote: post #14

Earlier quoted context omitted.

(a) This sentence doesn't make any sense. You can't "reverse" full SHA1 any more than you can "reverse" truncated SHA1. And SHA1 hashes are only 20 bytes long. Reversing isn't the attack. (b) The goal of the attack isn't to magically conjure the password; it's to magically conjure a searchlist of several tens of passwords, which is a game-changing improvement over a searchlist of, say, 72^8 passwords, or even tens of…

(a) I wrote in haste. Obviously it's a one way hash and unreversible. Additionally, I meant the first 20 characters, which is half of the full hash. (b) Obviously. Still extraordinarily difficult given this implementation IMO. But I take your point genuinely. (c) Agreed. If you weren't so friggin inflammatory I'd think we could come to a conclusion here. I could definitely be using a more lossy visualization to be mo…

You think running a dictionary through SHA1, generating little sparkline graphs for each hash (the same way you did in like 10 lines of JS code), and then carving the image into sectors and counting matches is "extraordinarily difficult"? Everything you need to do it is, I think, in Mochikit.

You get full props for grandma, her googles, and the palsy, although anything you could do to allow either of my grandmothers to log into the googles would qualify you for much more than HN props. I'm sorry you think I'm inflammatory, except you and I both know I'm not.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#22

Post by dfranke » Thu, Jul 09, 2009, 10:41 PM UTC

sho wrote: post #17

tptacek wrote: post #12

Earlier quoted context omitted.

Because those cameras can see my screen easily, and not my fingers typing on the screen? Because my fingers aren't perpendicular to the floor? Because even if I was going to concede that the image of the SHA graph was going to be fuzzy, just getting the vicinity of the color reduces my search space by 1/2^(16..24)? I love "cameras could eventually brute force" in your sentence, as if we were actually talking about so…

If someone is trying to learn your password from cameras nearby, they will make sure they can see your keyboard. Of course. If you're in that kind of hostile environment, nothing is safe except biometric or card authentication. Your concern is misplaced. You should have raised the scenario of, say, spying on a screen through a window from the other side of the street. That's a much better example and in that one, you…

There are plenty of scenarios where someone would be watching you type your password through a camera, but doesn't control placement of the camera. The most common case would be a security guard who is paid to monitor the cameras but had no hand in the design of the surveillance system.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#23

Post by TweedHeads » Thu, Jul 09, 2009, 10:49 PM UTC

Wow, besides its functionality or not, it is a really interesting approach to solving a problem.

Kudos for imagination.

Back to the initial problem, after successive attempts you may remember the shape and colors, problem is, most business complain new users can't remember their passwords after registering, so there won't be a second time.

The only way of better remembering something is by viewing it.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#24

Post by lhorie » Thu, Jul 09, 2009, 10:50 PM UTC

tptacek wrote: post #18

lhorie wrote: post #15

Earlier quoted context omitted.

>> model it against an adversary with a camera. Which can record your hands? :) I figure that the offline dictionary attack could be foiled if this was a Firefox extension that generated a random salt on installation. (of course, this doesn't work if you want to play WOW on an Internet Cafe) My main reaction to the experiment is that I don't know many people who touch type (at least when it comes to their password):…

Another thing I love about this discussion is the intimation ("big brother") that in order to get a picture of my screen, you have to be the NSA. And not, you know, some jackass with a camera.

Sure, sure, it could be both. It could be my girlfriend looking over my shoulder too. But of course, I don't use an stupidly easy password and I don't let my girlfriend see me typing it (2-finger typing style, of course). I mean who does that, right? :)

I just find it interesting to observe the discrepancies between perception of security and actual math-backed security.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#25

Post by TweedHeads » Thu, Jul 09, 2009, 10:52 PM UTC

Tip: instead of the himalayas try using a beachball.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#26

Post by sho » Thu, Jul 09, 2009, 11:03 PM UTC

dfranke wrote: post #22

sho wrote: post #17

Earlier quoted context omitted.

If someone is trying to learn your password from cameras nearby, they will make sure they can see your keyboard. Of course. If you're in that kind of hostile environment, nothing is safe except biometric or card authentication. Your concern is misplaced. You should have raised the scenario of, say, spying on a screen through a window from the other side of the street. That's a much better example and in that one, you…

There are plenty of scenarios where someone would be watching you type your password through a camera, but doesn't control placement of the camera. The most common case would be a security guard who is paid to monitor the cameras but had no hand in the design of the surveillance system.

I'm not saying it's a good idea, I'm saying that tptacek is overstating the risk compared to the far easier option of just spying on the keyboard.

And c'mon, no common security camera could pick up a usable copy of that little graph thing. Half the time they're not even colour. It would take specialised equipment. I was thinking more like thieves going to some rich person's house, finding a computer screen near a window, attaching a high-res camera and waiting for them to log on to internet banking, or something. Sure, in that situation, very bad risk. But geeze, if you're sitting in the Chinese embassy and logging on to the CIA web site using your fingers on a keyboard, tiny coloured graphs of your password hash are the least of your problems.

It is an interesting idea though. I don't like how much information is in the graph, but if it was reduced to just, say, a block of 16-bit colour, that might still be a useful hint to users. Probably more useful actually; the detailed graph is just confusing. And I don't think even tptacek would claim 16 bits of colour is much of a hint brute-forcing a 256 bit hash.

Taking that idea and running with it a little - you could even "salt" the colour randomly for each user, feeding the salt value into the JS. In fact, implementing a per-user salt for the system as proposed would eliminate all of tptacek's concerns. It wouldn't be the same across sites, but it would be consistent per site. I might suggest this as an improvement.

update: duh, the system wouldn't know which salt to load before the user logged in .. forget that idea. Unless it was stored in a cookie of course. Or could be loaded via AJAX when focus shifted out of the username field.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#27

Post by tptacek » Fri, Jul 10, 2009, 12:08 AM UTC

sho wrote: post #26

dfranke wrote: post #22

Earlier quoted context omitted.

There are plenty of scenarios where someone would be watching you type your password through a camera, but doesn't control placement of the camera. The most common case would be a security guard who is paid to monitor the cameras but had no hand in the design of the surveillance system.

I'm not saying it's a good idea, I'm saying that tptacek is overstating the risk compared to the far easier option of just spying on the keyboard. And c'mon, no common security camera could pick up a usable copy of that little graph thing. Half the time they're not even colour. It would take specialised equipment. I was thinking more like thieves going to some rich person's house, finding a computer screen near a win…

Salts. The "Hitler" of computer security discussions.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#28

Post by dfranke » Fri, Jul 10, 2009, 12:13 AM UTC

tptacek wrote: post #27

sho wrote: post #26

Earlier quoted context omitted.

I'm not saying it's a good idea, I'm saying that tptacek is overstating the risk compared to the far easier option of just spying on the keyboard. And c'mon, no common security camera could pick up a usable copy of that little graph thing. Half the time they're not even colour. It would take specialised equipment. I was thinking more like thieves going to some rich person's house, finding a computer screen near a win…

Salts. The "Hitler" of computer security discussions.

Nah, that'd be one-time pads.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#29

Post by sho » Fri, Jul 10, 2009, 12:52 AM UTC

tptacek wrote: post #27

sho wrote: post #26

Earlier quoted context omitted.

I'm not saying it's a good idea, I'm saying that tptacek is overstating the risk compared to the far easier option of just spying on the keyboard. And c'mon, no common security camera could pick up a usable copy of that little graph thing. Half the time they're not even colour. It would take specialised equipment. I was thinking more like thieves going to some rich person's house, finding a computer screen near a win…

Salts. The "Hitler" of computer security discussions.

Yeah, yeah. I'm waiting to hear how you could conceivably brute force the password from that graph (and only that graph) if it had a random per-user salt.

Re: HashMask - Another (More Secure) Experiment in Password Masking

#30

Post by tptacek » Fri, Jul 10, 2009, 1:10 AM UTC

sho wrote: post #29

tptacek wrote: post #27

Earlier quoted context omitted.

Salts. The "Hitler" of computer security discussions.

Yeah, yeah. I'm waiting to hear how you could conceivably brute force the password from that graph (and only that graph) if it had a random per-user salt.

I like the authentication system where you are guaranteed a nonce-bearing cookie identifying the user, but still forcing them to type their password. You know, just to be sure.

But I have an improvement on your system. Instead of a 16 bit salt, use a FIVE HUNDRED TWELVE bit salt. That's 32 times the saltiness! But just to trip evil hackers up, why don't you call that salt "PHPSESSIONID". I think that scheme is so salty that you only have to have users type their password just once!