Entries Tagged "cryptanalysis"

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KeeLoq Still Broken

That’s the key entry system used by Chrysler, Daewoo, Fiat, General Motors, Honda, Toyota, Lexus, Volvo, Volkswagen, Jaguar, and probably others. It’s broken:

The KeeLoq encryption algorithm is widely used for security relevant applications, e.g., in the form of passive Radio Frequency Identification (RFID) transponders for car immobilizers and in various access control and Remote Keyless Entry (RKE) systems, e.g., for opening car doors and garage doors.

We present the first successful DPA (Differential Power Analysis) attacks on numerous commercially available products employing KeeLoq. These so-called side-channel attacks are based on measuring and evaluating the power consumption of a KeeLoq device during its operation. Using our techniques, an attacker can reveal not only the secret key of remote controls in less than one hour, but also the manufacturer key of the corresponding receivers in less than one day. Knowing the manufacturer key allows for creating an arbitrary number of valid new keys and generating new remote controls.

We further propose a new eavesdropping attack for which monitoring of two ciphertexts, sent from a remote control employing KeeLoq code hopping (car key, garage door opener, etc.), is sufficient to recover the device key of the remote control. Hence, using the methods described by us, an attacker can clone a remote control from a distance and gain access to a target that is protected by the claimed to be “highly secure” KeeLoq algorithm.

We consider our attacks to be of serious practical interest, as commercial KeeLoq access control systems can be overcome with modest effort.

I’ve written about this before, but the above link has much better data.

EDITED TO ADD (4/4): A good article.

Posted on April 4, 2008 at 6:03 AM • View Comments

Cryptanalysis of A5/1

There have been a lot of articles about the new attack against the GSM cell phone encryption algorithm, A5/1. In some ways, this isn’t real news; we’ve seen A5/1 cryptanalysis papers as far back as ten years ago.

What’s new about this attack is: 1) it’s completely passive, 2) its total hardware cost is around $1,000, and 3) the total time to break the key is about 30 minutes. That’s impressive.

The cryptanalysis of A5/1 demonstrates an important cryptographic maxim: attacks always get better; they never get worse. This is why we tend to abandon algorithms at the first sign of weakness; we know that with time, the weaknesses will be exploited more effectively to yield better and faster attacks.

Posted on February 22, 2008 at 6:31 AM • View Comments

Cold Boot Attacks Against Disk Encryption

Nice piece of research:

We show that disk encryption, the standard approach to protecting sensitive data on laptops, can be defeated by relatively simple methods. We demonstrate our methods by using them to defeat three popular disk encryption products: BitLocker, which comes with Windows Vista; FileVault, which comes with MacOS X; and dm-crypt, which is used with Linux.

[…]

The root of the problem lies in an unexpected property of today’s DRAM memories. DRAMs are the main memory chips used to store data while the system is running. Virtually everybody, including experts, will tell you that DRAM contents are lost when you turn off the power. But this isn’t so. Our research shows that data in DRAM actually fades out gradually over a period of seconds to minutes, enabling an attacker to read the full contents of memory by cutting power and then rebooting into a malicious operating system.

Interestingly, if you cool the DRAM chips, for example by spraying inverted cans of “canned air” dusting spray on them, the chips will retain their contents for much longer. At these temperatures (around -50 °C) you can remove the chips from the computer and let them sit on the table for ten minutes or more, without appreciable loss of data. Cool the chips in liquid nitrogen (-196 °C) and they hold their state for hours at least, without any power. Just put the chips back into a machine and you can read out their contents.

This is deadly for disk encryption products because they rely on keeping master decryption keys in DRAM. This was thought to be safe because the operating system would keep any malicious programs from accessing the keys in memory, and there was no way to get rid of the operating system without cutting power to the machine, which “everybody knew” would cause the keys to be erased.

Our results show that an attacker can cut power to the computer, then power it back up and boot a malicious operating system (from, say, a thumb drive) that copies the contents of memory. Having done that, the attacker can search through the captured memory contents, find any crypto keys that might be there, and use them to start decrypting hard disk contents. We show very effective methods for finding and extracting keys from memory, even if the contents of memory have faded somewhat (i.e., even if some bits of memory were flipped during the power-off interval). If the attacker is worried that memory will fade too quickly, he can chill the DRAM chips before cutting power.

There seems to be no easy fix for these problems. Fundamentally, disk encryption programs now have nowhere safe to store their keys. Today’s Trusted Computing hardware does not seem to help; for example, we can defeat BitLocker despite its use of a Trusted Platform Module.

The paper is here; more info is here. Articles here.

There is a general security problem illustrated here: it is very difficult to secure data when the attacker has physical control of the machine the data is stored on. I talk about the general problem here, and it’s a hard problem.

EDITED TO ADD (2/26): How-to, with pictures.

Posted on February 21, 2008 at 1:29 PM • View Comments

Dutch RFID Transit Card Hacked

The Dutch RFID public transit card, which has already cost the government $2B—no, that’s not a typo—has been hacked even before it has been deployed:

The first reported attack was designed by two students at the University of Amsterdam, Pieter Siekerman and Maurits van der Schee. They analyzed the single-use ticket and showed its vulnerabilities in a report. They also showed how a used single-use card could be given eternal life by resetting it to its original “unused” state.

The next attack was on the Mifare Classic chip, used on the normal ticket. Two German hackers, Karsten Nohl and Henryk Plotz, were able to remove the coating on the Mifare chip and photograph the internal circuitry. By studying the circuitry, they were able to deduce the secret cryptographic algorithm used by the chip. While this alone does not break the chip, it certainly gives future hackers a stepping stone on which to stand. On Jan. 8, 2008, they released a statement abut their work.

Most of the links are in Dutch; there isn’t a whole lot of English-language press about this. But the Dutch Parliament recently invited the students to give testimony; they’re more than a little bit interested how $2B could be wasted.

My guess is the system was designed by people who don’t understand security, and therefore thought it was easy.

EDITED TO ADD (2/13): More info.

Posted on January 21, 2008 at 6:35 AM • View Comments

NASA Using 1960s Cryptanalysis Techniques

Well, sort of.

This paper from the Goddard Space Center, “NiCd Space Battery Test Data Analysis Project, Phase 2 Quarterly Report, 1 Jan. – 30 Apr. 1967,” uses “cryptanalytic techniques”—some sort of tri-gram frequency analysis, I think—to ferret out hidden clues about battery failures.

It’s hard to imagine non-NSA cryptography in the U.S. from the 1960s. Basically, it was all alphabetic stuff. Even rotor machines were highly classified, and absolutely nothing was being done in binary.

Posted on September 27, 2007 at 6:14 AM • View Comments

Breaking WEP in Under a Minute

WEP (Wired Equivalent Privacy) was the protocol used to secure wireless networks. It’s known to be insecure and has been replaced by Wi-Fi Protected Access, but it’s still in use.

This paper, “Breaking 104 bit WEP in less than 60 seconds,” is the best attack against WEP to date:

Abstract:

We demonstrate an active attack on the WEP protocol that is able to recover a 104-bit WEP key using less than 40.000 frames with a success probability of 50%. In order to succeed in 95% of all cases, 85.000 packets are needed. The IV of these packets can be randomly chosen. This is an improvement in the number of required frames by more than an order of magnitude over the best known key-recovery attacks for WEP. On a IEEE 802.11g network, the number of frames required can be obtained by re-injection in less than a minute. The required computational effort is approximately 2^20 RC4 key setups, which on current desktop and laptop CPUs in negligible.

Posted on April 4, 2007 at 12:46 PM • View Comments

More AACS Cracking

Slowly, AACS—the security in both Blu-ray and HD DVD—has been cracked. Now, it has been cracked even further:

Arnezami, a hacker on the Doom9 forum, has published a crack for extracting the “processing key” from a high-def DVD player. This key can be used to gain access to every single Blu-Ray and HD-DVD disc.

Previously, another Doom9 user called Muslix64 had broken both Blu-Ray and HD-DVD by extracting the “volume keys” for each disc, a cumbersome process. This break builds on Muslix64’s work but extends it—now you can break all AACS-locked discs.

As I have said before, what will be interesting to watch is how well HD DVD and Blu-ray recover. Both were built expecting these sorts of cracks, and both have mechanisms to recover security for future movies. It remains to be seen how well these recovery systems will work.

Posted on February 19, 2007 at 1:28 PM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.