Page 239

Terahertz Millimeter-Wave Scanners

Interesting article on terahertz millimeter-wave scanners and their uses to detect terrorist bombers.

The heart of the device is a block of electronics about the size of a 1990s tower personal computer. It comes housed in a musician’s black case, akin to the one Spinal Tap might use on tour. At the front: a large, square white plate, the terahertz camera and, just above it, an ordinary closed-circuit television (CCTV) camera. Mounted on a shelf inside the case is a laptop that displays the CCTV image and the blobby terahertz image side by side.

An operator compares the two images as people flow past, looking for unexplained dark areas that could represent firearms or suicide vests. Most images that might be mistaken for a weapon­—backpacks or a big patch of sweat on the back of a person’s shirt­—are easily evaluated by observing the terahertz image alongside an unaltered video picture of the passenger.

It is up to the operator­—in LA’s case, presumably a transport police officer­—to query people when dark areas on the terahertz image suggest concealed large weapons or suicide vests. The device cannot see inside bodies, backpacks or shoes. “If you look at previous incidents on public transit systems, this technology would have detected those,” Sotero says, noting LA Metro worked “closely” with the TSA for over a year to test this and other technologies. “It definitely has the backing of TSA.”

How the technology works in practice depends heavily on the operator’s training. According to Evans, “A lot of tradecraft goes into understanding where the threat item is likely to be on the body.” He sees the crucial role played by the operator as giving back control to security guards and allowing them to use their common sense.

I am quoted in the article as being skeptical of the technology, particularly how its deployed.

Tags: , , , ,

Posted on October 3, 2018 at 7:11 AM • View Comments

Sophisticated Voice Phishing Scams

Brian Krebs is reporting on some new and sophisticated phishing scams over the telephone.

I second his advice: “never give out any information about yourself in response to an unsolicited phone call.” Always call them back, and not using the number offered to you by the caller. Always.

EDITED TO ADD: In 2009, I wrote:

When I was growing up, children were commonly taught: “don’t talk to strangers.” Strangers might be bad, we were told, so it’s prudent to steer clear of them.

And yet most people are honest, kind, and generous, especially when someone asks them for help. If a small child is in trouble, the smartest thing he can do is find a nice-looking stranger and talk to him.

These two pieces of advice may seem to contradict each other, but they don’t. The difference is that in the second instance, the child is choosing which stranger to talk to. Given that the overwhelming majority of people will help, the child is likely to get help if he chooses a random stranger. But if a stranger comes up to a child and talks to him or her, it’s not a random choice. It’s more likely, although still unlikely, that the stranger is up to no good.

That advice is generalizable to this instance as well. The problem is that someone claiming to be from your bank asking for personal information. The problem is that they contacted you first.

Where else does this advice hold true?

Tags: , , ,

Posted on October 2, 2018 at 3:09 PM • View Comments

Facebook Is Using Your Two-Factor Authentication Phone Number to Target Advertising

From Kashmir Hill:

Facebook is not content to use the contact information you willingly put into your Facebook profile for advertising. It is also using contact information you handed over for security purposes and contact information you didn’t hand over at all, but that was collected from other people’s contact books, a hidden layer of details Facebook has about you that I’ve come to call “shadow contact information.” I managed to place an ad in front of Alan Mislove by targeting his shadow profile. This means that the junk email address that you hand over for discounts or for shady online shopping is likely associated with your account and being used to target you with ads.

Here’s the research paper. Hill again:

They found that when a user gives Facebook a phone number for two-factor authentication or in order to receive alerts about new log-ins to a user’s account, that phone number became targetable by an advertiser within a couple of weeks. So users who want their accounts to be more secure are forced to make a privacy trade-off and allow advertisers to more easily find them on the social network.

Tags: , , , , , , ,

Posted on October 2, 2018 at 5:53 AM • View Comments

More on the Five Eyes Statement on Encryption and Backdoors

Earlier this month, I wrote about a statement by the Five Eyes countries about encryption and back doors. (Short summary: they like them.) One of the weird things about the statement is that it was clearly written from a law-enforcement perspective, though we normally think of the Five Eyes as a consortium of intelligence agencies.

Susan Landau examines the details of the statement, explains what’s going on, and why the statement is a lot less than what it might seem.

Tags: , , , , , ,

Posted on October 1, 2018 at 6:22 AM • View Comments

Major Tech Companies Finally Endorse Federal Privacy Regulation

The major tech companies, scared that states like California might impose actual privacy regulations, have now decided that they can better lobby the federal government for much weaker national legislation that will preempt any stricter state measures.

I’m sure they’ll still do all they can to weaken the California law, but they know they’ll do better at the national level.

Tags: , ,

Posted on September 28, 2018 at 1:19 PM • View Comments

Counting People through a Wall with Wi-Fi

Interesting research:

In the team’s experiments, one WiFi transmitter and one WiFi receiver are behind walls, outside a room in which a number of people are present. The room can get very crowded with as many as 20 people zigzagging each other. The transmitter sends a wireless signal whose received signal strength (RSSI) is measured by the receiver. Using only such received signal power measurements, the receiver estimates how many people are inside the room ­ an estimate that closely matches the actual number. It is noteworthy that the researchers do not do any prior measurements or calibration in the area of interest; their approach has only a very short calibration phase that need not be done in the same area.

Academic paper.

Tags: , ,

Posted on September 27, 2018 at 7:43 AM • View Comments

Evidence for the Security of PKCS #1 Digital Signatures

This is interesting research: “On the Security of the PKCS#1 v1.5 Signature Scheme“:

Abstract: The RSA PKCS#1 v1.5 signature algorithm is the most widely used digital signature scheme in practice. Its two main strengths are its extreme simplicity, which makes it very easy to implement, and that verification of signatures is significantly faster than for DSA or ECDSA. Despite the huge practical importance of RSA PKCS#1 v1.5 signatures, providing formal evidence for their security based on plausible cryptographic hardness assumptions has turned out to be very difficult. Therefore the most recent version of PKCS#1 (RFC 8017) even recommends a replacement the more complex and less efficient scheme RSA-PSS, as it is provably secure and therefore considered more robust. The main obstacle is that RSA PKCS#1 v1.5 signatures use a deterministic padding scheme, which makes standard proof techniques not applicable.

We introduce a new technique that enables the first security proof for RSA-PKCS#1 v1.5 signatures. We prove full existential unforgeability against adaptive chosen-message attacks (EUF-CMA) under the standard RSA assumption. Furthermore, we give a tight proof under the Phi-Hiding assumption. These proofs are in the random oracle model and the parameters deviate slightly from the standard use, because we require a larger output length of the hash function. However, we also show how RSA-PKCS#1 v1.5 signatures can be instantiated in practice such that our security proofs apply.

In order to draw a more complete picture of the precise security of RSA PKCS#1 v1.5 signatures, we also give security proofs in the standard model, but with respect to weaker attacker models (key-only attacks) and based on known complexity assumptions. The main conclusion of our work is that from a provable security perspective RSA PKCS#1 v1.5 can be safely used, if the output length of the hash function is chosen appropriately.

I don’t think the protocol is “provably secure,” meaning that it cannot have any vulnerabilities. What this paper demonstrates is that there are no vulnerabilities under the model of the proof. And, more importantly, that PKCS #1 v1.5 is as secure as any of its successors like RSA-PSS and RSA Full-Domain.

Tags: , , , , ,

Posted on September 25, 2018 at 6:50 AM • View Comments

New Variants of Cold-Boot Attack

If someone has physical access to your locked—but still running—computer, they can probably break the hard drive’s encryption. This is a “cold boot” attack, and one we thought solved. We have not:

To carry out the attack, the F-Secure researchers first sought a way to defeat the the industry-standard cold boot mitigation. The protection works by creating a simple check between an operating system and a computer’s firmware, the fundamental code that coordinates hardware and software for things like initiating booting. The operating system sets a sort of flag or marker indicating that it has secret data stored in its memory, and when the computer boots up, its firmware checks for the flag. If the computer shuts down normally, the operating system wipes the data and the flag with it. But if the firmware detects the flag during the boot process, it takes over the responsibility of wiping the memory before anything else can happen.

Looking at this arrangement, the researchers realized a problem. If they physically opened a computer and directly connected to the chip that runs the firmware and the flag, they could interact with it and clear the flag. This would make the computer think it shut down correctly and that the operating system wiped the memory, because the flag was gone, when actually potentially sensitive data was still there.

So the researchers designed a relatively simple microcontroller and program that can connect to the chip the firmware is on and manipulate the flag. From there, an attacker could move ahead with a standard cold boot attack. Though any number of things could be stored in memory when a computer is idle, Segerdahl notes that an attacker can be sure the device’s decryption keys will be among them if she is staring down a computer’s login screen, which is waiting to check any inputs against the correct ones.

Tags: , , ,

Posted on September 24, 2018 at 6:52 AM • View Comments

← Earlier EntriesLater Entries →

Sidebar photo of Bruce Schneier by Joe MacInnis.