Entries Tagged "keys"

Page 12 of 13

Classical Crypto with Lasers

I simply don’t have the physics background to evaluate this:

Scheuer and Yariv’s concept for key distribution involves establishing a laser oscillation between the two users, who each decide how to reflect the light at their end by choosing one of three mirrors that peak at different frequencies.

Before a key is exchanged, the users reset the system by using the first mirror. Then they both randomly select a bit (either 1 or 0) and choose the corresponding mirror out of the other two, causing the lasing properties (wavelength and intensity) to shift in accordance with the mirror they chose. Because each user knows his or her own bit, they can determine the value of each other’s bits; but an eavesdropper, who doesn’t know either bit, could only figure out the correlation between bits, but not the bits themselves. Similar to quantum key distribution systems, the bit exchange is successful in about 50% of the cases.

“For a nice analogy, consider a very large ‘justice scale’ where Alice is at one side and Bob is at the other,” said Scheuer. “Both Alice and Bob have a set of two weights (say one pound representing ‘0’ and two pounds representing ‘1’). To exchange a bit, Alice and Bob randomly select a bit and put the corresponding weight on the scales. If they pick different bits, the scales will tilt toward the heavy weight, thus indicating who picked ‘1’ and who picked ‘0.’ If however, they choose the same bit, the scales will remain balanced, regardless whether they (both) picked ‘0’ or ‘1.’ These bits can be used for the key because Eve, who in this analogy can only observe the tilt of the scales, cannot deduce the exchanged bit (in the previous case, Eve could deduce the bits). Of course, there are some differences between the laser concept and the scales analogy: in the laser system, the successful bit exchanges occur when Alice and Bob pick opposite bits, and not identical; also, there is the third state needed for resetting the laser, etc. But the underlying concept is the same: the system uses some symmetry properties to ‘calculate’ the correlation between the bits selected in each side, and it reveals only the correlation. For Alice and Bob, this is enough–but not for Eve.”

But this quote gives me pause:

Although users can’t easily detect an eavesdropper here, the system increases the difficulty of eavesdropping “almost arbitrarily,” making detecting eavesdroppers almost unnecessary.

EDITED TO ADD (11/6): Here’s the paper.

Posted on November 6, 2006 at 7:49 AMView Comments

Expensive Cameras in Checked Luggage

This is a blog post about the problems of being forced to check expensive camera equipment on airplanes:

Well, having lived in Kashmir for 12+ years I am well accustomed to this type of security. We haven’t been able to have hand carries since 1990. We also cannot have batteries in any of our equipment checked or otherwise. At least we have been able to carry our laptops on and recently been able to actually use them (with the batteries). But, if things keep moving in this direction, and I’m sure it will, we need to start thinking now about checking our cameras and computers and how to do it safely.
This is a very unpleasant idea. Two years ago I ordered a Canon 20D and had it “hand carried” over to meet me in England by a friend. My friend put it in their checked bag. The bag never showed up. She did not have insurance and all I got $100 from British Airways for the camera and $500 from American Express (buyers protection) that was it. So now it looks as if we are going to have to check our cameras and our computers involuntarily. OK here are a few thoughts.

Pretty basic stuff, and we all know about the risks of putting expensive stuff in your checked luggage.

The interesting part is one of the blog comments, about halfway down. Another photographer wonders if the TSA rules for firearms could be extended to camera equipment:

Why not just have the TSA adopt the same check in rules for photographic and video equipment as they do for firearms?

All firearms must be in checked baggage, no carry on.

All firearms must be transported in a locked, hard sided case using a non-TSA approved lock. This is to prevent anyone from opening the case after its been screened.

After bringing the equipment to the airline counter and declaring and showing the contents to the airline representative, you take it over to the TSA screening area where it it checked by a screener, relocked in front of you, your key or keys returned to you (if it’s not a combination lock) and put directly on the conveyor belt for loading onto the plane.

No markings, stickers or labels identifying what’s inside are put on the outside of the case or, if packed inside something else, the bag.

Might this solve the problem? I’ve never lost a firearm when flying.

Then someone has the brilliant suggestion of putting a firearm in your camera-equipment case:

A “weapons” is defined as a rifle, shotgun, pistol, airgun, and STARTER PISTOL. Yes, starter pistols – those little guns that fire blanks at track and swim meets – are considered weapons…and do NOT have to be registered in any state in the United States.

I have a starter pistol for all my cases. All I have to do upon check-in is tell the airline ticket agent that I have a weapon to declare…I’m given a little card to sign, the card is put in the case, the case is given to a TSA official who takes my key and locks the case, and gives my key back to me.

That’s the procedure. The case is extra-tracked…TSA does not want to lose a weapons case. This reduces the chance of the case being lost to virtually zero.

It’s a great way to travel with camera gear…I’ve been doing this since Dec 2001 and have had no problems whatsoever.

I have to admit that I am impressed with this solution.

Posted on September 22, 2006 at 12:17 PMView Comments

What is a Hacker?

A hacker is someone who thinks outside the box. It’s someone who discards conventional wisdom, and does something else instead. It’s someone who looks at the edge and wonders what’s beyond. It’s someone who sees a set of rules and wonders what happens if you don’t follow them. A hacker is someone who experiments with the limitations of systems for intellectual curiosity.

I wrote that last sentence in the year 2000, in my book Secrets and Lies. And I’m sticking to that definition.

This is what else I wrote in Secrets and Lies (pages 43-44):

Hackers are as old as curiosity, although the term itself is modern. Galileo was a hacker. Mme. Curie was one, too. Aristotle wasn’t. (Aristotle had some theoretical proof that women had fewer teeth than men. A hacker would have simply counted his wife’s teeth. A good hacker would have counted his wife’s teeth without her knowing about it, while she was asleep. A good bad hacker might remove some of them, just to prove a point.)

When I was in college, I knew a group similar to hackers: the key freaks. They wanted access, and their goal was to have a key to every lock on campus. They would study lockpicking and learn new techniques, trade maps of the steam tunnels and where they led, and exchange copies of keys with each other. A locked door was a challenge, a personal affront to their ability. These people weren’t out to do damage — stealing stuff wasn’t their objective — although they certainly could have. Their hobby was the power to go anywhere they wanted to.

Remember the phone phreaks of yesteryear, the ones who could whistle into payphones and make free phone calls. Sure, they stole phone service. But it wasn’t like they needed to make eight-hour calls to Manila or McMurdo. And their real work was secret knowledge: The phone network was a vast maze of information. They wanted to know the system better than the designers, and they wanted the ability to modify it to their will. Understanding how the phone system worked — that was the true prize. Other early hackers were ham-radio hobbyists and model-train enthusiasts.

Richard Feynman was a hacker; read any of his books.

Computer hackers follow these evolutionary lines. Or, they are the same genus operating on a new system. Computers, and networks in particular, are the new landscape to be explored. Networks provide the ultimate maze of steam tunnels, where a new hacking technique becomes a key that can open computer after computer. And inside is knowledge, understanding. Access. How things work. Why things work. It’s all out there, waiting to be discovered.

Computers are the perfect playground for hackers. Computers, and computer networks, are vast treasure troves of secret knowledge. The Internet is an immense landscape of undiscovered information. The more you know, the more you can do.

And it should be no surprise that many hackers have focused their skills on computer security. Not only is it often the obstacle between the hacker and knowledge, and therefore something to be defeated, but also the very mindset necessary to be good at security is exactly the same mindset that hackers have: thinking outside the box, breaking the rules, exploring the limitations of a system. The easiest way to break a security system is to figure out what the system’s designers hadn’t thought of: that’s security hacking.

Hackers cheat. And breaking security regularly involves cheating. It’s figuring out a smart card’s RSA key by looking at the power fluctuations, because the designers of the card never realized anyone could do that. It’s self-signing a piece of code, because the signature-verification system didn’t think someone might try that. It’s using a piece of a protocol to break a completely different protocol, because all previous security analysis only looked at protocols individually and not in pairs.

That’s security hacking: breaking a system by thinking differently.

It all sounds criminal: recovering encrypted text, fooling signature algorithms, breaking protocols. But honestly, that’s just the way we security people talk. Hacking isn’t criminal. All the examples two paragraphs above were performed by respected security professionals, and all were presented at security conferences.

I remember one conversation I had at a Crypto conference, early in my career. It was outside amongst the jumbo shrimp, chocolate-covered strawberries, and other delectables. A bunch of us were talking about some cryptographic system, including Brian Snow of the NSA. Someone described an unconventional attack, one that didn’t follow the normal rules of cryptanalysis. I don’t remember any of the details, but I remember my response after hearing the description of the attack.

“That’s cheating,” I said.

Because it was.

I also remember Brian turning to look at me. He didn’t say anything, but his look conveyed everything. “There’s no such thing as cheating in this business.”

Because there isn’t.

Hacking is cheating, and it’s how we get better at security. It’s only after someone invents a new attack that the rest of us can figure out how to defend against it.

For years I have refused to play the semantic “hacker” vs. “cracker” game. There are good hackers and bad hackers, just as there are good electricians and bad electricians. “Hacker” is a mindset and a skill set; what you do with it is a different issue.

And I believe the best computer security experts have the hacker mindset. When I look to hire people, I look for someone who can’t walk into a store without figuring out how to shoplift. I look for someone who can’t test a computer security program without trying to get around it. I look for someone who, when told that things work in a particular way, immediately asks how things stop working if you do something else.

We need these people in security, and we need them on our side. Criminals are always trying to figure out how to break security systems. Field a new system — an ATM, an online banking system, a gambling machine — and criminals will try to make an illegal profit off it. They’ll figure it out eventually, because some hackers are also criminals. But if we have hackers working for us, they’ll figure it out first — and then we can defend ourselves.

It’s our only hope for security in this fast-moving technological world of ours.

This essay appeared in the Summer 2006 issue of 2600.

Posted on September 14, 2006 at 7:13 AMView Comments

Snake-Oil Research in Nature

Snake-oil isn’t only in commercial products. Here’s a piece of research published (behind a paywall) in Nature that’s just full of it.

The article suggests using chaos in an electro-optical system to generate a pseudo-random light sequence, which is then added to the message to protect it from interception. Now, the idea of using chaos to build encryption systems has been tried many times in the cryptographic community, and has always failed. But the authors of the Nature article show no signs of familiarity with prior cryptographic work.

The published system has the obvious problem that it does not include any form of message authentication, so it will be trivial to send spoofed messages or tamper with messages while they are in transit.

But a closer examination of the paper’s figures suggests a far more fundamental problem. There’s no key. Anyone with a valid receiver can decode the ciphertext. No key equals no security, and what you have left is a totally broken system.

I e-mailed Claudio R. Mirasso, the corresponding author, about the lack of any key, and got this reply: “To extract the message from the chaotic carrier you need to replicate the carrier itself. This can only be done by a laser that matches the emitter characteristics within, let’s say, within 2-5%. Semiconductor lasers with such similarity have to be carefully selected from the same wafer. Even though you have to test them because they can still be too different and do not synchronize. We talk abut a hardware key. Also the operating conditions (current, feedback length and coupling strength) are part of the key.”

Let me translate that. He’s saying that there is a hardware key baked into the system at fabrication. (It comes from manufacturing deviations in the lasers.) There’s no way to change the key in the field. There’s no way to recover security if any of the transmitters/receivers are lost or stolen. And they don’t know how hard it would be for an attacker to build a compatible receiver, or even a tunable receiver that could listen to a variety of encodings.

This paper would never get past peer review in any competent cryptography journal or conference. I’m surprised it was accepted in Nature, a fiercely competitive journal. I don’t know why Nature is taking articles on topics that are outside its usual competence, but it looks to me like Nature got burnt here by a lack of expertise in the area.

To be fair, the paper very carefully skirts the issue of security, and claims hardly anything: “Additionally, chaotic carriers offer a certain degree of intrinsic privacy, which could complement (via robust hardware encryption) both classical (software based) and quantum cryptography systems.” Now that “certain degree of intrinsic privacy” is approximately zero. But other than that, they’re very careful how they word their claims.

For instance, the abstract says: “Chaotic signals have been proposed as broadband information carriers with the potential of providing a high level of robustness and privacy in data transmission.” But there’s no disclosure that this proposal is bogus, from a privacy perspective. And the next-to-last paragraph says “Building on this, it should be possible to develop reliable cost-effective secure communication systems that exploit deeper properties of chaotic dynamics.” No disclosure that “chaotic dynamics” is actually irrelevant to the “secure” part. The last paragraph talks about “smart encryption techniques” (referencing a paper that talks about chaos encryption), “developing active eavesdropper-evasion strategies” (whatever that means), and so on. It’s just enough that if you don’t parse their words carefully and don’t already know the area well, you might come away with the impression that this is a major advance in secure communications. It seems as if it would have helped to have a more careful disclaimer.

Communications security was listed as one of the motivations for studying this communications technique. To list this as a motivation, without explaining that their experimental setup is actually useless for communications security, is questionable at best.

Meanwhile, the press has written articles that convey the wrong impression. Science News has an article that lauds this as a big achievement for communications privacy.

It talks about it as a “new encryption strategy,” “chaos-encrypted communication,” “1 gigabyte of chaos-encrypted information per second.” It’s obvious that the communications security aspect is what Science News is writing about. If the authors knew that their scheme is useless for communications security, they didn’t explain that very well.

There is also a New Scientist article titled “Let chaos keep your secrets safe” that characterizes this as a “new cryptographic technique, ” but I can’t get a copy of the full article.

Here are two more articles that discuss its security benefits. In the latter, Mirasso says “the main task we have for the future” is to “define, test, and calibrate the security that our system can offer.”

And their project web page says that “the continuous increase of computer speed threatens the safety” of traditional cryptography (which is bogus) and suggests using physical-layer chaos as a way to solve this. That’s listed as the goal of the project.

There’s a lesson here. This is research undertaken by researchers with no prior track record in cryptography, submitted to a journal with no background in cryptography, and reviewed by reviewers with who knows what kind of experience in cryptography. Cryptography is a subtle subject, and trying to design new cryptosystems without the necessary experience and training in the field is a quick route to insecurity.

And what’s up with Nature? Cryptographers with no training in physics know better than to think they are competent to evaluate physics research. If a physics paper were submitted to a cryptography journal, the authors would likely be gently redirected to a physics journal — we wouldn’t want our cryptography conferences to accept a paper on a subject they aren’t competent to evaluate. Why would Nature expect the situation to be any different when physicists try to do cryptography research?

Posted on December 7, 2005 at 6:36 AMView Comments

RFID Car Keys

RFID car keys (subscription required) are becoming more popular. Since these devices broadcast a unique serial number, it’s only a matter of time before a significant percentage of the population can be tracked with them.

Lexus has made what it calls the “SmartAccess” keyless-entry system standard on its new IS sedans, designed to compete with German cars like the BMW 3 series or the Audi A4, as well as rivals such as the Infiniti G35 or the U.S.-made Cadillac CTS. BMW offers what it calls “keyless go” as an option on the new 3 series, and on its higher-priced 5, 6 and 7 series sedans.

Volkswagen AG’s Audi brand offers keyless-start systems on its A6 and A8 sedans, but not yet on U.S.-bound A4s. Cadillac’s new STS sedan, big brother to the CTS, also offers a pushbutton start.

Starter buttons have a racy flair — European sports cars and race cars used them in the past. The proliferation of starter buttons in luxury sedans has its roots in theft protection. An increasing number of cars now come with theft-deterrent systems that rely on a chip in the key fob that broadcasts a code to a receiver in the car. If the codes don’t match, the car won’t start.

Cryptography can be used to make these devices anonymous, but there’s no business reason for automobile manufacturers to field such a system. Once again, the economic barriers to security are far greater than the technical ones.

Posted on October 5, 2005 at 8:13 AMView Comments

Fingerprint-Lock Failure in a Prison

So much for high-tech security:

Prison officers have been forced to abandon a new security system and return to the use of keys after the cutting-edge technology repeatedly failed.

The system, which is thought to have cost over £3 million, used fingerprint recognition to activate the locking system at the high-security Glenochil Prison near Tullibody, Clackmannanshire.

After typing in a PIN code, prison officers had to place their finger on a piece of glass. Once the print was recognised, they could then lock and unlock prison doors.

However, problems arose after a prisoner demonstrated to wardens that he could get through the system at will. Other prisoners had been doing the same for some time.

Unfortunately, the article doesn’t say how the prisoners hacked the system. Perhaps they lifed fingerprints off readers with transparent tape. Or perhaps the valid latent fingerprints left on the readers by wardens could be activated somehow.

I would really like some more details here. Does it really make sense to have a tokenless access system in a prison? I don’t know enough to answer that question.

Posted on September 26, 2005 at 4:03 PMView Comments

Shoulder Surfing Keys

Here’s a criminal who “stole” keys, the physical metal ones, by examining images of them being used:

He surreptitiously videotaped letter carriers as they opened the boxes, zooming in on their keys. Lau used those images to calculate measurements for the grooves in the keys and created brass duplicates.

[…]

“The FBI is not aware of anything else like this,” bureau spokeswoman Jerri Williams said.

Technology causes security imbalances. Sometimes those imbalances favor the defender, and sometimes they favor the attacker. What we have here is a new application of a technology by an attacker.

Very clever.

Posted on September 7, 2005 at 11:35 AMView Comments

The Keys to the Sydney Subway

Global secrets are generally considered poor security. The problems are twofold. One, you cannot apply any granularity to the security system; someone either knows the secret or does not. And two, global secrets are brittle. They fail badly; if the secret gets out, then the bad guys have a pretty powerful secret.

This is the situation right now in Sydney, where someone stole the master key that gives access to every train in the metropolitan area, and also starts them.

Unfortunately, this isn’t a thief who got lucky. It happened twice, and it’s possible that the keys were the target:

The keys, each of which could start every train, were taken in separate robberies within hours of each other from the North Shore Line although police believed the thefts were unrelated, a RailCorp spokeswoman said.

The first incident occurred at Gordon station when the driver of an empty train was robbed of the keys by two balaclava-clad men shortly after midnight on Sunday morning.

The second theft took place at Waverton Station on Sunday night when a driver was robbed of a bag, which contained the keys, she said.

So, what can someone do with the master key to the Sydney subway? It’s more likely a criminal than a terrorist, but even so it’s definitely a serious issue:

A spokesman for RailCorp told the paper it was taking the matter “very seriously,” but would not change the locks on its trains.

Instead, as of Sunday night, it had increased security around its sidings, with more patrols by private security guards and transit officers.

The spokesman said a “range of security measures” meant a train could not be stolen, even with the keys.

I don’t know if RailCorp should change the locks. I don’t know the risk: whether that “range of security measures” only protects against train theft — an unlikely scenario, if you ask me — or other potential scenarios as well. And I don’t know how expensive it would be to change the locks.

Another problem with global secrets is that it’s expensive to recover from a security failure.

And this certainly isn’t the first time a master key fell into the wrong hands:

Mr Graham said there was no point changing any of the metropolitan railway key locks.

“We could change locks once a week but I don’t think it reduces in any way the security threat as such because there are 2000 of these particular keys on issue to operational staff across the network and that is always going to be, I think, an issue.”

A final problem with global secrets is that it’s simply too easy to lose control of them.

Moral: Don’t rely on global secrets.

Posted on September 1, 2005 at 8:06 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.