Schneier on Security

Clive Robinson • April 12, 2010 9:57 AM

Back in World War One they did the same thing but to hide ships it was known as “Dazzle camouflage” and it worked on the “optical illusion confusion” principle.

That is it caused an operator using an optical range finder (using the split image coincidence effect) to be sufficiently unsure of what they where looking at. Thus unable to take an accurate range by aligning the image.

Dazzel was invented in 1916 by the artist Norman Wilkinson. It was still in use during the second world war on the arctic convoys where it helped hid a vessal in amongst ice fields etc.

http://en.wikipedia.org/wiki/Dazzle_camouflage

Clive Robinson • April 12, 2010 12:15 PM

@ BF Skinner,

Of course the question is as you note if this works at making the system not detect a face let alone recognise who it is,

How little make up is required to foil recognition.

Which is as you may remember a question I was asking a little while ago about the (supposed) Mossad “hit people” in Dubai.

I wonder if “facial putty” etc could do the same job but less obviously to humans.

Lets be honest if I had a nose that looked like Ron Moody’s “Fagin” or a chin that looked like Jimmy Hill’s, people would (I hope) not say anything to my face out of social necesity.

As I understand it most FC systems work not on “direct measurment” but “releative measurment”.

So although I might not be able to change the real measurment between my eyes I might will be able to change other relative measurments to say my cheak bones and chin or teeth so that relativly my eyws look closer or further apart, and thus have a different ratio that is not mine in the DB.

Clive Robinson • April 12, 2010 12:55 PM

For those interested in facial recognition systems there is sadly not much info out there (yes I know it’s available in Apple’s iLife software and some online photo DB’s).

There are one or two (out of date) articles one of which is,

http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/facial-recognition.htm

However since 9/11 FRsystems have gone underground and it has been suggested that this is deliberate to get “funding” from various UK and US three letter agencies.

What is known that most systems that have been tested on CCTV systems have been far from a success.

Apparently Boston Airport (Logan) tried two full face systems but got little better than 61% correct recognition and a system that has been running in the London Borough of Newham has not spotted on criminal on the streets even thought there are quite a few “known offenders” living in the borough who are in the database.

Also the Australian SmartGate software using bio-metric passports appears no where as good as people are led to belive.

Clive Robinson • April 13, 2010 2:17 AM

@ SB7,

“The most important part is that this scheme counters ONLY Haar-face based detection algorithms. That’s just like only defending against bombs-in-shoes but not bombs generally, and it has the same drawbacks.”

You are arguing that it “counters only Haar…”, when it has “only been tested against Haar…”.

The two are not the same thus you cannot say it does not work against other “face detecting” systems untill either it has been tested against them or you can show good grounds for your reasoning. Nor can you argue that it does not work against “face recognition” systems for the same reasons.

Further there are two distinct uses for FR systems,

1, Is this face a match for the credential presented.

2, Does this face match any in the “rouges gallary” DB.

In the first you should actually be looking to “disprove” the match (ie pick up on differences)

In the second you should initialy be looking for similarities (data base reducing searches are “and” not “or”).

In the general case “Face detecting” is only going to be used for the latter system.

It would appear that untill 9/11 FDsystems where not investigated that much, and most of the improvments in FR (not FD) where by automaticaly adjusting for “off full face” 2D presentation and other “real time” issues.

And few people have publicaly looked into the various forms of “deception” that might work against either FR or FD systems.

But we do know some FR systems designers have given up on 2D presentation and are now using 3D presentation.

However 3D presentation has distinct limitations in that it works only when the test subject is within a relativly short distance of the stereo camera. And this causes a much increased system cost.

Normaly as a system designer you would not opt to make a “fundementaly limiting” design choice unless there where good reasons to do so. Likewise you would normaly chose the least costly system that works.

So some of the designers of FR systems are certainly aware of 2D presentation short commings and thus may well be aware of the issues of “deception” as they have opted to go for a fundementaly different and considerably more expensive way of building FR systems.

As for your comment,

“… and they do; IR is unreliable for biometrics…”

I for one would be interested to know what you base that on. There are a number of biometric systems that do use “near visable” IR just more effectivly for scanning objects (including faces) for two reasons,

1, Because the human eye is insensitive to it and it does not cause the iris to change.

2, The sensors and optics actualy work better at those wavelengths.