Chances are that you’re familiar with the National Security Agency as the U.S. government organization that listens in on foreign communications and cracks their encrypted messages for useful intelligence.
While foreign communications surveillance is agency's main purpose, no everyone knows that it's also heavily involved with protecting sensitive government communications from interception and decryption by foreign intelligence agencies.
This means the NSA is deeply involved in developing encryption standards that are as uncrackable as possible. But not just uncrackable now, the encryption standards have to withstand the test of time and remain uncrackable long into the future. That test of time can include developing cryptography that can defeat the potential massive power of a large quantum computer, even though nothing of that sort currently exists.
“A lot of classified data has a long lifetime,” said Neal Ziring, NSA Capabilities Technical Director. He said that this is because it’s in hardware that takes a long time to get into the field and that once put into service, lasts a long time. Such items may include Navy ships (which remain in service for decades) or spacecraft (which can be in service even longer).
Because the data the government uses can last a very long time, the NSA is already working on ways to protect the data against capabilities that currently exist only in a very limited form. Such a capability is quantum computing, which might be limited today, but promises to be a critical technology in the decades to come.
Ziring said that for commercial users that don’t necessarily have to consider such long timeframes, it’s still worth preparing for post-quantum security because the industry and the markets are heading in that direction. He said standards bodies that certify encryption are working on such standards and that the industry needs to be ready to implement encryption that can withstand assaults by quantum computers when the capability arrives.
The reason that the NSA and other security and encryption researchers worry about quantum computing isn’t just because it can result in very fast computers. It’s because such computers can run complex algorithms that can’t be used efficiently using classical digital computers. That's because quantum computers can use quantum superposition.
A qubit, or a quantum bit, is a quantum unit of information which can have many positions between the normal states of 0 and 1, and in fact can occupy all of those states at the same time. This means that a qubit can encode an infinite amount of information, at least until the state of the qubit is observed at which point it collapses into a single state.