Quantum teleportation achieved over ten miles of free space

Quantum teleportation has achieved a new milestone or, should we say, a new ten-milestone: scientists have recently had success teleporting information between photons over a free space distance of nearly ten miles, an unprecedented length. The researchers who have accomplished this feat note that this brings us closer to communicating information without needing a traditional signal, and that the ten miles they have reached could span the distance between the surface of the earth and space.
  "Quantum teleportation" is quite different from how many people imagine teleportation to work. Rather than picking one thing up and placing it somewhere else, quantum teleportation involves entangling two things, like photons or ions, so their states are dependent on one another and each can be affected by the measurement of the other's state.
When one of the items is sent a distance away, entanglement ensures that changing the state of one causes the other to change as well, allowing the teleportation of quantum information, if not matter. However, the distance particles can be from each other has been limited so far to a number of meters.
Teleportation over distances of a few hundred meters has previously only been accomplished with the photons traveling in fiber channels to help preserve their state. In this particular experiment, researchers maximally entangled two photons using both spatial and polarization modes and sent the one with higher energy through a ten-mile-long free space channel. They found that the distant photon was still able to respond to changes in state of the photon they held onto even at this unprecedented distance.
However, the long-distance teleportation of a photon is only a small step towards developing applications for the procedure. While photons are good at transmitting information, they are not as good as ions at allowing manipulation, an advancement we'd need for encryption. Researchers were also able to maintain the fidelity of the long-distance teleportation at 89 percent— decent enough for information, but still dangerous for the whole-body human teleportation that we're all looking forward to.

By Casey Johnston
Science, 2010. DOI: 10.1038/NPHOTON.2010.87  (About DOIs).  

Secure computers aren’t so secure

Even well-defended computers can leak shocking amounts of private data. MIT researchers seek out exotic attacks in order to shut them down

You may update your antivirus software religiously, immediately download all new Windows security patches, and refuse to click any e-mail links ostensibly sent by your bank, but even if your computer is running exactly the way it’s supposed to, a motivated attacker can still glean a shocking amount of private information from it. The time it takes to store data in memory, fluctuations in power consumption, even the sounds your computer makes can betray its secrets. MIT researchers centered at the Computer Science and Artificial Intelligence Lab’s Cryptography and Information Security Group (CIS) study such subtle security holes and how to close them.

In 2005, Eran Tromer, now a postdoc at CIS, and colleagues at the Weizmann Institute in Rehovot, Israel, showed that without any breach of security in the ordinary sense, a seemingly harmless computer program could eavesdrop on other programs and steal the type of secret cryptographic key used by one of the most common Internet encryption schemes. Armed with the key, an attacker could steal a computer user’s credit card number, bank account password — whatever the encryption scheme was invoked to protect.

Computer operating systems are supposed to prevent any given program from looking at the data stored by another. But when two programs are running at the same time, they sometimes end up sharing the same cache — a small allotment of high-speed memory where the operating system stores frequently used information. Tromer and his colleagues showed that simply by measuring how long it took to store data at a number of different cache locations, a malicious program could determine how frequently a cryptographic system was using those same locations. “The memory access patterns — that is, which memory addresses are accessed — are heavily influenced by the specific secret key being used in that operation,” Tromer says. “We demonstrated a concise and efficient procedure for learning the secret keys given just this crude information about the memory access patterns.” Complete extraction of the private key, Tromer says, “takes merely seconds, and the measurements that are needed, of the actual cryptographic process being attacked, can be carried out in milliseconds.”

The encryption system that Tromer was attacking, called AES, was particularly vulnerable because it used tables of precalculated values as a computational short cut, so that encoding and decoding messages wouldn’t be prohibitively time consuming. Since Tromer and his colleagues published their results, Intel has added hardware support for AES to its chips, so that Internet encryption software won’t have to rely on such “lookup tables.”

In a statement, Intel told the MIT News Office that its decision “was mainly motivated by the performance/efficiency benefits achieved,” but that “in addition, there is a potential security benefit since these new instructions can mitigate the possibility of software side channel attacks on AES that have been described in research papers, including those discovered by Tromer, Percival, and Bernstein.”

“I think it’s fair to say that it’s a direct response to the cache-timing attacks against AES,” Pankaj Rohatgi, director of hardware security at the data security firm Cryptography Research, says of Intel’s move.

Together with CIS cofounder Ron Rivest and CSAIL’s Saman Amarasinghe, Tromer is trying to develop further techniques for thwarting cache attacks by disrupting the correlations between encryption keys and memory access patterns. A couple weeks ago, at the Association for Computing Machinery’s Symposium on Operating Systems Principles, the researchers announced that they had a “proof-of-concept prototype” of a defense system, but they plan to continue testing and refining it before publishing any papers.

Tromer has also been investigating whether cloud computing — the subcontracting of computational tasks to networked servers maintained by companies like Amazon and Google — is susceptible to cache attacks. Many web sites rely on cloud computing to handle sudden surges in their popularity: renting added server space for a few hours at a time can be much cheaper than maintaining large banks of proprietary servers that frequently stand idle.

The word “cloud” is supposed to suggest that this vast agglomeration of computing power is amorphous and constantly shifting, but Tromer and colleagues at the University of California, San Diego, were able to load their eavesdropping software onto precisely the same servers that were hosting websites they’d targeted in advance. In part, their approach involved spreading their software across a number of servers, then assailing a targeted website with traffic. By spying on the caches of the servers hosting their software, they could determine which were also trying to keep pace with their fake traffic spikes. Once they’d identified the target site’s servers, they could use cache monitoring to try to steal secrets.

“Imagine a stock broker that specializes in a specific company,” Tromer says. “If you observe that his virtual machine is particularly active, that could be valuable information. Or you may want to know how popular your competitors’ website is. We’ve actually demonstrated that we can very robustly estimate web server popularity.”

“This has sparked the imagination of both the research community and industry,” Rohatgi says. “I interact with a lot of people in industry, and when they say, ‘Give me the technical basis for this,’ I point to [Tromer and colleagues’] papers.”

Finally, Tromer is continuing work he began as a graduate student, on the use of a “hundred-dollar commodity microphone” to record the very sounds emitted by a computer and analyze them for information about cryptographic keys. So far, Tromer hasn’t been able to demonstrate complete key extraction, but he believes he’s getting close.

Any information at all about a computer’s internal workings “is actually fairly damaging,” Rohatgi says. “In some sense, some of these cryptographic algorithms are fairly brittle, and with a little extra information, you can break them.”

Larry Hardesty, MIT News Office

Quantum Secrets: A New Standard in Crytopgraphy?

Quantum cryptography has been a Holy Grail for security researchers since the idea was proposed, the promise of a new standard in absolutely unbreakable communications. But it's a new standard in the Microsoft sense: "Use our brilliant new system, because we're making sure the old one doesn't work anymore."

The most common security algorithm used online is RSA, an encryption system designed by MIT researchers Ron Rivest, Adi Shamir and Leonard Adlemen in 1977 (hence RSA, Rivest-Shamir-Adlemen). The idea is that any numerical code can be cracked, so rather than try to invent one that's unbreakable you settle for one that would take a really long time - everybody involved is dead because the sun has exploded five billion years later kind of long time. The system is scalable too - every time computers improve, you just make your RSA bit-string longer to exponentially increase the processing power needed to crack it before the user dies of old age.

That's where quantum computers come in. They operate using "qubits" which can be in every possible state at once - so an eight-qubit system could represent every possible 8 regular-bit piece of data. It still collapses into just one regular 8-bit state when you look at it, so the quantum nature of the data was just a mathematical oddity until MIT Professor Peter Shor came up with an algorithm that could access this "every possible state" property to crack the RSA problem. Since then the race to build a quantum computer has been running in earnest.

However, quantum mechanics also promises a replacement for the redundant RSA. Key codes can be transmitted in pairs of particles in such a way that they can't be copied, and these keys can then be used to make a truly uncrackable code. By uncopiable, we mean that the act of a spy even looking at the keycode will destroy it - and the receiver immediately knows to use a different one. This is known as Quantum Key Distribution (QKD), and an EU Initiative for "Secure Communication based on Quantum Cryptography" (SEQOQC) claims it will demonstrate a network-ready version of the technology this October in Vienna. You can be sure security experts worldwide will be paying close attention, as well as a couple of 00-agents and possibly Q.

But you have to be careful of the hype. While the theory of quantum communications promises absolute security, there's a lot of room between theory and actual practice for problems. Researchers at the University of Toronto have already demonstrated a successful spy-attack on a commercial QKD device, based on particular aspects of hardware not quite delivering the idealized situation. Because you'll always have people messing things up. Remember - you can use the very basic physics of the universe to transmit an absolutely secure code around the globe, but you can't stop the person at the other end writing it on a yellow sticky on the side of their monitor.

Posted by Luke McKinney.