16 January 2014

Single-use computer memories may emerge as gold standard for secure transactions

by Will Parker

Computer security systems may one day get a boost from quantum physics, as a result of recent research into a "one-shot" memory unit, whose contents can be read only a single time.

The research, by Yi-Kai Liu from the National Institute of Standards and Technology, is being presented this week at Princeton's Innovations in Theoretical Computer Science conference. Liu's work shows how the laws of quantum physics could allow for the construction of single-use memory devices.

Liu says one-shot memories would have a wide range of possible applications but would be especially suited to controlling financial transactions. For example, a one-shot memory might contain two authorization codes: one that credits the recipient's bank account and one that credits the sender's bank account, in case the transfer is cancelled. Crucially, the memory could only be read once, so only one of the codes can be retrieved, and hence, only one of the two actions can be performed - not both.

Liu's approach involves storing the data using quantum bits (qubits), which use quantum properties such as magnetic spin to represent digital information. By using a technique called "conjugate coding," Liu explains that two secret messages (such as separate authorization codes) can be encoded into the same string of qubits, so that a user can retrieve either one of the two messages. But as the qubits can only be read once, the user cannot retrieve both.

Liu concedes that the quantum phenomenon of entanglement, where two particles can affect each other even when separated by great distances, could potentially throw a spanner into the works. "If an adversary is able to utilize entanglement, he can retrieve both messages at once, breaking the security of the scheme," he explained.

However, Liu has observed that in certain kinds of physical systems, it is very difficult to create and utilize entanglement. In fact, he shows in his paper that this obstacle turns out to be an advantage. "It's fascinating how entanglement - and the lack thereof - is the key to making this work," he said. "From a practical point of view, these quantum devices would be more expensive to fabricate, but they would provide a higher level of security. To protect critical systems, we don't want to rely too much on complex defenses that might still get hacked. It's better if we can rely on fundamental laws of nature, which are unassailable."

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Source: National Institute of Standards and Technology