According to documents provided by former NSA contractor Edward Snowden, the effort to build “a cryptologically useful quantum computer” — a machine exponentially faster than classical computers — is part of a $79.7 million research program titled “Penetrating Hard Targets.” Much of the work is hosted under classified contracts at a laboratory in College Park, Md.
The development of a quantum computer has long been a goal of many in the scientific community, with revolutionary implications for fields such as medicine as well as for the NSA’s code-breaking mission. With such technology, all current forms of public key encryption would be broken, including those used on many secure Web sites as well as the type used to protect state secrets. . . .
The basic principle underlying quantum computing is known as “quantum superposition,” the idea that an object simultaneously exists in all states. A classical computer uses binary bits, which are either zeroes or ones. A quantum computer uses quantum bits, or qubits, which are simultaneously zero and one.
This seeming impossibility is part of the mystery that lies at the heart of quantum theory, which even theoretical physicists say no one completely understands.
“If you think you understand quantum mechanics, you don’t understand quantum mechanics,” said the late Nobel laureate Richard Feynman, who is widely regarded as the pioneer in quantum computing.
Here’s how it works, in theory: While a classical computer, however fast, must do one calculation at a time, a quantum computer can sometimes avoid having to make calculations that are unnecessary to solving a problem. That allows it to home in on the correct answer much more quickly and efficiently.
Quantum computing is difficult to attain because of the fragile nature of such computers. In theory, the building blocks of such a computer might include individual atoms, photons or electrons. To maintain the quantum nature of the computer, these particles would need to be carefully isolated from their external environments.
“Quantum computers are extremely delicate, so if you don’t protect them from their environment, then the computation will be useless,” said Daniel Lidar, a professor of electrical engineering and the director of the Center for Quantum Information Science and Technology at the University of Southern California.
A working quantum computer would open the door to easily breaking the strongest encryption tools in use today, including a standard known as RSA, named for the initials of its creators. RSA scrambles communications, making them unreadable to anyone but the intended recipient, without requiring the use of a shared password. It is commonly used in Web browsers to secure financial transactions and in encrypted e-mails. RSA is used because of the difficulty of factoring the product of two large prime numbers. Breaking the encryption involves finding those two numbers. This cannot be done in a reasonable amount of time on a classical computer.
In 2009, computer scientists using classical methods were able to discover the primes within a 768-bit number, but it took almost two years and hundreds of computers to factor it. The scientists estimated that it would take 1,000 times longer to break a 1,024-bit encryption key, which is commonly used for online transactions.
A large-scale quantum computer, however, could theoretically break a 1,024-bit encryption much faster. Some leading Internet companies are moving to 2,048-bit keys, but even those are thought to be vulnerable to rapid decryption with a quantum computer.
Quantum computers have many applications for today’s scientific community, including the creation of artificial intelligence. But the NSA fears the implications for national security.
“The application of quantum technologies to encryption algorithms threatens to dramatically impact the US government’s ability to both protect its communications and eavesdrop on the communications of foreign governments,” according to an internal document provided by Snowden.
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