Cryptographers Are Discovering New Rules for Quantum Encryption

The archetypal version of this story appeared successful Quanta Magazine.

Say you privation to nonstop a backstage message, formed a concealed vote, oregon motion a papers securely. If you bash immoderate of these tasks connected a computer, you’re relying connected encryption to support your information safe. That encryption needs to withstand attacks from codification breakers with their ain computers, truthful modern encryption methods trust connected assumptions astir what mathematical problems are hard for computers to solve.

But arsenic cryptographers laid the mathematical foundations for this attack to accusation information successful the 1980s, a fewer researchers discovered that computational hardness wasn’t the lone mode to safeguard secrets. Quantum theory, primitively developed to recognize the physics of atoms, turned retired to person heavy connections to accusation and cryptography. Researchers recovered ways to basal the information of a fewer circumstantial cryptographic tasks straight connected the laws of physics. But these tasks were unusual outliers—for each others, determination seemed to beryllium nary alternate to the classical computational approach.

By the extremity of the millennium, quantum cryptography researchers thought that was the extremity of the story. But successful conscionable the past fewer years, the tract has undergone different seismic shift.

“There’s been this rearrangement of what we judge is imaginable with quantum cryptography,” said Henry Yuen, a quantum accusation theorist astatine Columbia University.

In a drawstring of caller papers, researchers person shown that astir cryptographic tasks could inactive beryllium accomplished securely adjacent successful hypothetical worlds wherever practically each computation is easy. All that matters is the trouble of a peculiar computational occupation astir quantum mentation itself.

“The assumptions you request tin beryllium way, way, mode weaker,” said Fermi Ma, a quantum cryptographer astatine the Simons Institute for the Theory of Computing successful Berkeley, California. “This is giving america caller insights into computational hardness itself.”

This Message Will Self-Destruct

The communicative begins successful the precocious 1960s, erstwhile a physics postgraduate pupil named Stephen Wiesner started reasoning astir the destructive quality of measurement successful quantum theory. Measure immoderate strategy governed by the rules of quantum physics, and you’ll change the quantum authorities that mathematically describes its configuration. This quantum measurement disturbance was a hindrance for astir physicists. Wiesner, who took an unorthodox information-centric presumption of quantum theory, wondered whether it could beryllium made useful. Perhaps it could service arsenic a signifier of built-in tamper extortion for delicate data.

But Wiesner’s ideas were excessively acold up of their time, and helium near academia aft postgraduate school. Fortunately, he’d discussed his ideas with his person and chap physicist Charles Bennett, who unsuccessfully tried to involvement others successful the taxable for a decade. Finally, successful 1979, Bennett met the machine idiosyncratic Gilles Brassard portion swimming disconnected the seashore of Puerto Rico during a conference. Together, they wrote a groundbreaking paper describing a caller attack to an important cryptographic task. Their protocol was based connected quantum measurement disturbance, and needed nary assumptions astir the trouble of immoderate computational problems.