francis@cs.ua.oz.au (Francis Vaughan) (05/07/91)
In article <050691.224256WDBURNS%MTUS5.BITNET>, WDBURNS%MTUS5.BITNET (William D. Burns) writes: |> Greetings netlanders! |> |> Quick question: |> Our university library installed one of those anti-theft walk-thru |> devices and I was wondering how the little bugger works. |> |> Observations: |> 1) When walking thru with Walkman (tm sony) on TAPE-playback, I heard |> 4 or 5 very short, high frequence "clicks" thru my headphones. (Of |> course I had to go back thru again to hear 'em again! :) They swear |> that this device is safe for magnetic media (i.e. disks). |> |> 2) In the binding of the library's books was a strip of paper (dimensions |> of 5 X .25 inches) that had evenly-spaced metal strips in it. |> |> 3) To allow a book to pass thru without setting off all the alarms, the |> library person runs the book binding over a bulk-eraser type thing. |> |> So, how does this little thing work? Is it sending a low energy magnetic |> pulses out and picking up and strange resonances from the little strip? Or |> is the wave RF in nature? The former. As I understand it the little chunks of metal are a very interesting magnetic material. It has a different hysterysis curve depending upon its state of magnetization. In one state of magnetisation the curve has very pointy edges, so if you drive it around the end of the curve with an alternating field, as it is driven over the point it emits a bit of RF. The metal strip that the little chunks are bonded to may act as an antenna helping to propogate the signal. So if you are trying to steal a book, you walk through the alternating field, and a detector is looking for little pulses of RF that are synchronous with the field. If they are there it squarks. When you borrow the book the librarian degausses (or maybe magnetises, intuitivly I suspect degausing) the chunks in the book so changing the shape of the curve to have more rounded corners and hence no RF pulsing out. Returned books get the reverse treatment. The field strength of the detector can be quite low, it only needs to drive around one corner of the hysterysis curve. Magnetic media should be safe. Pacemakers however may be a different story. Maybe someone else can provide some more specific info, and/or corrections. Francis Vaughan.
ropg@ooc.uva.nl (Rop Gonggrijp) (05/08/91)
They mostly work as follows:
In the book is a strip of metal (any metal) covered by a piece of ferrite.
The ferrite is magnetised, thus changing the frequency at which this gizmo
resonates (it is covered in plastic, so it does resonate).
If they demagnetize the ferrite the thing goes to a lower resonating freq.
One end of the gate emits the first (high) frequency and the other end detects
it. A sudden drop in power means something is 'stealing' energy / resonating
and thus the alarm is activated.
These systems usually work at 915 MHz or so....... Have fun beating it
Oh, by the way, if you transmit this freq. and then play with the transmitted
power you should be able to make the bell ring at quite considderable distance.
--
Rop Gonggrijp (ropg@ooc.uva.nl) is also editor of Hack-Tic (hack/phreak mag.)
quote: "We don't care about freedom of the mind, | Postbus 22953 (in DUTCH)
freedom of signature will do just fine" | 1100 DL AMSTERDAM
Any opinions in this posting are wasted on you | tel: +31 20 6001480ART100@psuvm.psu.edu (Andy Tefft) (05/08/91)
I have a friend who uses an electric wheelchair, and at his local video store, the alarm goes off when he leaves the store, but not when he comes in (you go through the detector either way), whether he has any movies (properly desensitized) or not. Why would this be?
svaldez@sdcc13.ucsd.edu (Basshead ) (05/08/91)
In article <19934@slice.ooc.uva.nl>, ropg@ooc.uva.nl (Rop Gonggrijp) writes: > They mostly work as follows: > > In the book is a strip of metal (any metal) covered by a piece of ferrite. > The ferrite is magnetised, thus changing the frequency at which this gizmo > resonates (it is covered in plastic, so it does resonate). > > If they demagnetize the ferrite the thing goes to a lower resonating freq. > > One end of the gate emits the first (high) frequency and the other end detects > it. A sudden drop in power means something is 'stealing' energy / resonating > and thus the alarm is activated. > > These systems usually work at 915 MHz or so....... Have fun beating it > > Oh, by the way, if you transmit this freq. and then play with the transmitted > power you should be able to make the bell ring at quite considderable distance. This is a reasonable assumption, but if there is any scientific argument against what I say, please correct me. In clothing stores at the local mall, I've heard that thieves are able to often defeat the security systems a lot of stores use -- the ones with the detectors across the entrance and the big plastic tags on the unpurchased clothing which is removed at the counter -- anyways they are able to shoplift merchandise by placing clothes into a bag completely lined with foil... Now, I assume if you did the same to a book you could theoretically shield the book (completely wrapped) from the RF energy emitted by the gates.? I'm not an EE major but this seems reasonable -- ?????? -- -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=-*=-=*=- University of California, San Diego - ICC e-mail: gyro@ucsd.edu "DOS sucks!"
wdp@ee.egr.duke.edu (William D. Palmer) (05/09/91)
In reference to your posting: > From: ART100@psuvm.psu.edu (Andy Tefft) > Date: 8 May 91 03:02:28 GMT > I have a friend who uses an electric wheelchair ... (Stuff about theft detection device deleted.) > Why would this be? Try getting him to go out backwards. If that gives you the same response as coming in, there's some non-symmetry in the magnetic metal parts on the chair that's disturbing the theft detection device. Dev Palmer wdp@dukee.egr.duke.edu Duke Electrical Engineering Room 309 Old Engineering Bldg. Durham, NC 27706 (919) 660-5282 "I'm from North Carolina and I DON'T support Jesse Helms!"
rambler@pnet51.orb.mn.org (Dan Meyer) (05/09/91)
WDBURNS%MTUS5.BITNET (William D. Burns) writes: >Greetings netlanders! > >Quick question: > Our university library installed one of those anti-theft walk-thru > devices and I was wondering how the little bugger works. > > Observations: > 1) When walking thru with Walkman (tm sony) on TAPE-playback, I heard > 4 or 5 very short, high frequence "clicks" thru my headphones. (Of > course I had to go back thru again to hear 'em again! :) They swear > that this device is safe for magnetic media (i.e. disks). > > 2) In the binding of the library's books was a strip of paper (dimensions > of 5 X .25 inches) that had evenly-spaced metal strips in it. > > 3) To allow a book to pass thru without setting off all the alarms, the > library person runs the book binding over a bulk-eraser type thing. > >So, how does this little thing work? Is it sending a low energy magnetic >pulses out and picking up and strange resonances from the little strip? Or >is the wave RF in nature? > >Just an enquiring mind wanting to know. :) > >Bill As I understand the system in use here in the Twin Cities Metro area, *any* book that passes through the detectors will sound the alarm. the reason the alarm does not go off when you check out books is the librarian passes the books *around* the detector. If you don't believe me, check out a book, and then go back in and the back out with the book. -- Dan Remember: " Buffalo never Oink " Seen on a South Dakota travel brocure. Advertisment: Try the Railway Post Office , a railfan BBS ! (612) 377-2197. UUCP: {crash tcnet}!orbit!pnet51!rambler INET: rambler@pnet51.orb.mn.org
rice@willow23.cray.com (Jonathan Rice) (05/10/91)
In article <19934@slice.ooc.uva.nl> ropg@ooc.uva.nl (Rop Gonggrijp) writes: >They mostly work as follows: >In the book is a strip of metal (any metal) covered by a piece of ferrite. >The ferrite is magnetised, thus changing the frequency at which this gizmo >resonates (it is covered in plastic, so it does resonate). > [much more fascinating electroinformation deleted...] I can give you an example of how one particular system worked. The St. Paul public library, 4th St. branch (the main one), had the usual detector pylons by the exit door, with the familiar warning notices. And there were gizmos, to borrow Mr. Gonggrijp's technical term, in the books. Apparently, though, the checker-outers of books found that it slowed them down too much to have to quell the gizmos, so the entire system was turned off for more than a year. The theft prevention device was nothing more than the expectation created by the signs and detectors. Good old psychology. Of course, when this was divulged, nobody was willing to say how well it had worked. I've no idea if they ever turned it back on again. -- Jonathan C. Rice | Internet: rice@cray.com | UUCP: uunet!cray!rice
erickson@crevas.enet.dec.com (John Erickson) (05/13/91)
In article <100921.10755@timbuk.cray.com>, rice@willow23.cray.com (Jonathan Rice) writes... >In article <19934@slice.ooc.uva.nl> ropg@ooc.uva.nl (Rop Gonggrijp) writes: >> [much more fascinating electroinformation deleted...] > >Apparently, though, the checker-outers of books found that it slowed them >down too much to have to quell the gizmos, so the entire system was turned >off for more than a year. The theft prevention device was nothing more than >the expectation created by the signs and detectors. > Very interesting --- this is generally the practice at video stores around here. No effort is made to "un-do" the "gizmo" planted in the video's box; the check-out person simplies slides the video along the counter, away from the gizmo-detectors. Everyone leaving the store, however, must pass _through_ the detectors, and pick up the rented videos on the other side. I believe my local library has adopted a similar practice. The logistical relationship between most older library checkouts and their exit doors probably necessitate that the "un-do" scheme still be use, however. *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* * John Erickson * crevas::erickson * * Advanced Test Development * erickson@crevas.dec.com * * Digital Equipment Corp. * ...!decwrl!crevas.dec.com!erickson * * Acton, MA 01720 * erickson%crevas.dec@decwrl.dec.com * *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
popyackl@lonex.radc.af.mil (Leonard J. Popyack) (05/13/91)
In article <91127.230228ART100@psuvm.psu.edu> ART100@psuvm.psu.edu (Andy Tefft) writes: >I have a friend who uses an electric wheelchair, and >at his local video store, the alarm goes off when he leaves the >store, but not when he comes in (you go through the detector either >way), whether he has any movies (properly desensitized) or not. >Why would this be? try going through backwards.
rbrink@hubcap.clemson.edu (Rick Brink) (05/14/91)
From article <1991May13.124937.4956@e2big.mko.dec.com>, by erickson@crevas.enet.dec.com (John Erickson): > In article <100921.10755@timbuk.cray.com>, rice@willow23.cray.com (Jonathan Rice) writes... >>In article <19934@slice.ooc.uva.nl> ropg@ooc.uva.nl (Rop Gonggrijp) writes: >>> [much more fascinating electroinformation deleted...] >> >>Apparently, though, the checker-outers of books found that it slowed them >>down too much to have to quell the gizmos, so the entire system was turned >>off for more than a year. The theft prevention device was nothing more than >>the expectation created by the signs and detectors. There are 2 distinctly different types of systems. One has active components in the books, the other has a passive component in the book. It depends on which security fairy godmother talked to the business, as to which type of system they chose. Both can work very well, when deligently installed and serviced. As has been mentioned, may places don't have the patience to get it working correctly. Many environmental things can and do affect the sensitivity of the detectors. 3M's system (ours) works well for us. We keep it on, and we test it daily. Of course, with all the little hints and direct information presented in discussions here, there are now thousands of people who know how to beat it. But I hope they are understanding when they visit their local library, and after searching for a reference that is crutial to their research, are told that the book is missing from the collection. You help crooks steal, and eventally they will steal from YOU. rbrink@hubcap.clemson.edu Clemson University Libraries Rick Brink, Information Resource Coordiantor III
cy5@cunixa.cc.columbia.edu (Conway Yee) (05/14/91)
In article rbrink@hubcap.clemson.edu (Rick Brink) writes: > >There are 2 distinctly different types of systems. One has active components >in the books, the other has a passive component in the book. It depends on >which security fairy godmother talked to the business, as to which type of >system they chose. Both can work very well, when deligently installed and >serviced. As has been mentioned, may places don't have the patience to get >it working correctly. Many environmental things can and do affect the >sensitivity of the detectors. 3M's system (ours) works well for us. We keep >it on, and we test it daily. Of course, with all the little hints and direct >information presented in discussions here, there are now thousands of people >who know how to beat it. But I hope they are understanding when they visit >their local library, and after searching for a reference that is crutial to >their research, are told that the book is missing from the collection. You >help crooks steal, and eventally they will steal from YOU. Ah, yet another advocate of security by obscurity! This has shown not to be incredibly effective. You should always assume that "the enemy" has general knowledge of your security or crypto system. If a system can be broken, it will be broken. One of the effects of security by obscurity is to promote complacency. Bug fixes do not get installed (because nobody knows about the bug), propagation of bug fixes is hindered, and discoveries of bugs are hindered. Remember, "the enemy" is not hindered by such policies. Frequently, when a bug is uncovered, word of mouth spreads rather rapidly. Conway Yee, N2JWQ yee@ming.mipg.upenn.edu (preferred) 231 S. Melville St. cy5@cunixa.cc.columbia.edu (forwarded to above) Philadelphia, Pa 19139 yee@bnlx26.nsls.bnl.gov (rarely checked) (215) 386-1312
bur@ultisol.gsfc.nasa.gov (M.J.C. Bur) (05/15/91)
In article <1991May14.152521.7935@hubcap.clemson.edu> rbrink@hubcap.clemson.edu (Rick Brink) writes: >Of course, with all the little hints and direct >information presented in discussions here, there are now thousands of people >who know how to beat it. But I hope they are understanding when they visit >their local library, and after searching for a reference that is crutial to >their research, are told that the book is missing from the collection. You >help crooks steal, and eventally they will steal from YOU. > >rbrink@hubcap.clemson.edu >Clemson University Libraries >Rick Brink, Information Resource Coordiantor III In case you forgot the name of the group Rick, it's sci.electronics. In this group we discuss things relating to electronic technology. What people turn around and use the information for is their business. Being an "Information Resource Coordiantor III" I wouldn't think you would advocate that we censor our posts but maybe I'm reading you wrong. Personally I found the posts relating to the anti-theft devices interesting, not because I'm planing to steal anything, but because I am a curious person. Just because people know how to defeat your security system doesn't mean they will. I'm sure everyone reading this knows of several ways to kill another person but that doesn't mean they will. Besides, if someone wanted to steal your books couldn't they just drop them out a window and go around and pick them up later? :-) Information is not the problem, (some) people are. Mike -- ------------------------------------------------------------------ M.J.C. Bur | Internet: bur@ultisol.gsfc.nasa.gov NASA/GSFC Code 923 |------------------------------------------ Greenbelt, MD 20771 | Disclaimer!? Hell, I don't even know 'er
rbrink@hubcap.clemson.edu (Rick Brink) (05/15/91)
From article <1991May14.155250.25003@cunixf.cc.columbia.edu>, by cy5@cunixa.cc.columbia.edu (Conway Yee): > In article rbrink@hubcap.clemson.edu (Rick Brink) writes: >> >>There are 2 distinctly different types of systems. One has active components >>in the books, the other has a passive component in the book. It depends on > shit deleted > Ah, yet another advocate of security by obscurity! This has shown not to > be incredibly effective. You should always assume that "the enemy" has > general knowledge of your security or crypto system. If a system can be > broken, it will be broken. One of the effects of security by obscurity > is to promote complacency. Bug fixes do not get installed (because nobody > knows about the bug), propagation of bug fixes is hindered, and discoveries > of bugs are hindered. Remember, "the enemy" is not hindered by such policies. > Frequently, when a bug is uncovered, word of mouth spreads rather rapidly. > > Conway Yee, N2JWQ > yee@ming.mipg.upenn.edu (preferred) 231 S. Melville St. > cy5@cunixa.cc.columbia.edu (forwarded to above) Philadelphia, Pa 19139 > yee@bnlx26.nsls.bnl.gov (rarely checked) (215) 386-1312 I get so tired of this ying/yang squabling. Which came first, the thief or the stolen property. In the real world, things cost money. Public libraries don't have Billion dollar budgets to spend on security systems. All they are there for is to discourage people from thinking it's ok to steal. In some alternate universe, libraries require NMR's of patron coming in and out. All items have specific atomic stuctures that go critical when removed from the security bubble, ad nasum. We're not talking about the library at Oak Ridge or SRC, we're talking about public libraries and Video stores. Yep, Conway, you are correct in your observation that we have our heads burried in the sand if we think we can keep Electrical Engineers from figuring out our little secret. But was it too much to expect that Electrical Engineers who figure it out, keep their professional mouths shut about it. (Sorry guys/gals I don't mean to malign you or your professions, you're just people who might know how...). Suppose I decided I liked the idea of people swallowing capsules full of cynanide, and wanted more people to be able to create perfect counterfitpackaging to distribute it. Gee, I guess you'd point a finger (if asked) at Bristol Myers and say "gee guys, you should have designed a package that was homicidal maniac proof. I'd suggest one that required Retinal Scanns to open, and had at least 10 megabites of ROM instructions, limiting who is allowed to us it. It all boils down to a long lost concept of "Public Trust." The general public was supposed to trust business, government, etc. to do the right things. Well, they broke the trust. Now, far to many average citizens feel like "they broke it first, so now I get to screw everyone I can, before they get it going again." If you don't think it's important to control your self, or to encourage your neighors to be in control, government will catch up with it and control it for you. The "save us from the bad guns" Brady Bill is a current example. Weather it works to stop gun crimes or not is irrelevant. We are all, by our complacency, molding a new society, where it is OK for some Asshole in charge, to decide just how we will live tomorrow. His opinion will most likely differ from our own. Gee, I think we need to have all news feeds censored, and people who talk about the wrong things on them, will be arested. Or better yet, we'll shot them and ask questions later. This type of nonsense (my own diatribe included) just serves to endanger the freedom of the nets. If we police ourselves, we don't have to worry about someone else doing it for us.
phil@ux1.cso.uiuc.edu (Phil Howard KA9WGN) (05/15/91)
rbrink@hubcap.clemson.edu (Rick Brink) writes: >little secret. But was it too much to expect that Electrical Engineers who >figure it out, keep their professional mouths shut about it. (Sorry guys/gals Yeah... that is too much to expect. Technical knowledge usually has more that one application. Also the ways to defeat many existant systems are actually trivial anyway. Most of us don't steal nor do we expect vary many of the rest of us to steal. If I knew for a fact that someone WOULD steal if I were to tell him how, I would not tell him. Absent that fact, the information is just technology, not a method to steal. >If we police ourselves, we don't have to worry about someone else doing it >for us. But police ourselves from what? Technology? Take the current cellular telephone system for example. It is illegal to listen in to cellular phone communications. Yet you can do so with a modified scanner. Would it be appropriate for me to post how to modify as scanner to do so? I think it would be OK because there are OTHER legitimate reasons to listen to those particular frequencies, for things other than listening to cellular telephone (such as hams wanting to detect potentially interfering emissions of harmonics from defective transmitters they are operating). I see nothing wrong with describing how something works. We also have the technology to make things work in such a way that even someone who knows how it works can't break it anyway. The problem is that we don't use this technology. -- /***************************************************************************\ / Phil Howard -- KA9WGN -- phil@ux1.cso.uiuc.edu | Guns don't aim guns at \ \ Lietuva laisva -- Brivu Latviju -- Eesti vabaks | people; CRIMINALS do!! / \***************************************************************************/
newman@theory.tn.cornell.edu (Bill Newman) (05/15/91)
In article <1991May14.202632.3500@ux1.cso.uiuc.edu> phil@ux1.cso.uiuc.edu (Phil Howard KA9WGN) writes: >I see nothing wrong with describing how something works. > There are good arguments for this. >We also have the technology to make things work in such a way that even >someone who knows how it works can't break it anyway. The problem is that >we don't use this technology. > For the problem described in the title, this is not a good argument. What kind of anti-theft device do you have in mind? Powerful gamma ray sources on the books? Perhaps magnetic monopoles? Any economical device I know of can be blocked. And a thorough search of random customers is, well, a pain in the ass. For computer security and cryptography, you can make systems which are invulnerable even when your opponent knows what you are doing. For this kind of application, truly secure technology seems out of reach. Bill Newman newman@theory.tn.cornell.edu
newsham@wiliki.eng.hawaii.edu (Timothy Newsham) (05/20/91)
In article <3206@sirius.ucs.adelaide.edu.au> francis@cs.adelaide.edu.au writes: > >When you borrow the book the librarian degausses (or maybe magnetises, >intuitivly >I suspect degausing) the chunks in the book so changing the shape of the curve >to have more rounded corners and hence no RF pulsing out. Returned books get >the reverse treatment. > >Maybe someone else can provide some more specific info, and/or corrections. > > Francis Vaughan. So if i really wanted a book alls i gotta do is run upstairs to the audio visual center and use their bulk tape eraser??? hmm.. interesting Tim Newsham