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A representation of how TLS works.

Nadhem J. AlFardan and Kenneth G. Paterson

Software developers are racing to patch a recently discovered vulnerability that allows attackers to recover the plaintext of authentication cookies and other encrypted data as they travel over the Internet and other unsecured networks.

The discovery is significant because in many cases it makes it possible for attackers to completely subvert the protection provided by the secure sockets layer and transport layer protocols. Together, SSL, TLS, and a close TLS relative known as Datagram Transport Layer Security are the sole cryptographic means for websites to prove their authenticity and to encrypt data as it travels between end users and Web servers. The so-called "Lucky Thirteen" attacks devised by computer scientists to exploit the weaknesses work against virtually all open-source TLS implementations, and possibly implementations supported by Apple and Cisco Systems as well. (Microsoft told the researchers it has determined its software isn't susceptible.)

The attacks are extremely complex, so for the time being, average end users are probably more susceptible to attacks that use phishing e-mails or rely on fraudulently issued digital certificates to defeat the Web encryption protection. Nonetheless, the success of the cryptographers' exploits—including the full plaintext recovery of data protected by the widely used OpenSSL implementation—has clearly gotten the attention of the developers who maintain those programs. Already, the Opera browser and PolarSSL have been patched to plug the hole, and developers for OpenSSL, NSS, and CyaSSL are expected to issue updates soon.

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Enlarge / An overview of a chosen-prefix collision. A similar technique was used by the Flame espionage malware that targeted Iran. The scientific novelty of the malware underscored the sophistication of malware sponsored by wealthy nation states.

Marc Stevens

The dance among blackhat, whitehat, and greyhat hackers grew ever more intricate in 2012, thanks to a steady stream of exploits, vulnerability discoveries, and data breaches. In-the-wild attacks against Internet Explorer, the Java software framework, and other perennial favorites continued, of course. They inflicted plenty of damage on end users, but given their familiarity, they hardly stood out.

What got our attention were attacks on entirely new classes of devices or victims, or in the case of passwords and cryptography, the culmination of new exploit techniques quickly eroding the protection we once took for granted.

From our perspective, here are the five biggest security stories this year.

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Enlarge / A slide from Steube's presentation outlining a more efficient way to crack passwords protected by the SHA1 cryptographic algorithm.

A researcher has devised a method that reduces the time and resources required to crack passwords that are protected by the SHA1 cryptographic algorithm.

The optimization, presented on Tuesday at the Passwords^12 conference in Oslo, Norway, can speed up password cracking by 21 percent. The optimization works by reducing the number of steps required to calculate SHA1 hashes, which are used to cryptographically represent strings of text so passwords aren't stored as plain text. Such one-way hashes—for example 5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8 to represent "password" (minus the quotes) and e38ad214943daad1d64c102faec29de4afe9da3d for "password1"—can't be mathematically unscrambled, so the only way to reverse one is to run plaintext guesses through the same cryptographic function until an identical hash is generated.

Jens Steube—who is better known as Atom, as the pseudonymous developer of the popular Hashcat password-recovery program—figured out a way to remove identical computations that are performed multiple times from the process of generating of SHA1 hashes. By precalculating several steps ahead of time, he's able to skip the redundant steps, shaving 21 percent of the time required to crack large numbers of passwords. Slides from Tuesday's presentation are here.

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Enlarge / A diagram of a side-channel attack on a virtual machine. Using a malicious VM running on the same hardware, scientists were able to recover a private encryption key.

Zhang et al.

Piercing a key defense found in cloud environments such as Amazon's EC2 service, scientists have devised a virtual machine that can extract private cryptographic keys stored on a separate virtual machine when it resides on the same piece of hardware.

The technique, unveiled in a research paper published by computer scientists from the University of North Carolina, the University of Wisconsin, and RSA Laboratories, took several hours to recover the private key for a 4096-bit ElGamal-generated public key using the libgcrypt v.1.5.0 cryptographic library. The attack relied on "side-channel analysis," in which attackers crack a private key by studying the electromagnetic emanations, data caches, or other manifestations of the targeted cryptographic system.

One of the chief selling points of virtual machines is their ability to run a variety of tasks on a single computer rather than relying on a separate machine to run each one. Adding to the allure, engineers have long praised the ability of virtual machines to isolate separate tasks, so one can't eavesdrop or tamper with the other. Relying on fine-grained access control mechanisms that allow each task to run in its own secure environment, virtual machines have long been considered a safer alternative for cloud services that cater to the rigorous security requirements of multiple customers.

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