There's a day coming when the locks on the internet stop working. Security researchers already have a name for it

[Dylan]

Almost every secure connection you make online, your bank, your email, your messaging apps, relies on math problems that are extremely easy to set up but painfully hard to reverse, multiplying two enormous prime numbers together is trivial, but figuring out which two primes were multiplied to get a given result is not, at least not for any computer that exists today. Security researchers have started calling the hypothetical future moment when a quantum computer finally becomes powerful enough to reverse that math Q-Day, deliberately echoing the old Y2K scare to convey a similar sense of a countdown clock

The unsettling part is that the risk does not actually start on Q-Day itself, it starts today. Intelligence agencies and cybersecurity researchers describe a strategy called harvest now, decrypt later, where an adversary simply intercepts and stores encrypted data right now, with no ability to read it yet, and simply waits. Once a capable enough quantum computer eventually exists, all of that stockpiled data becomes readable retroactively, which is a genuinely strange kind of security threat, the theft already happened, you just do not know it yet

This is exactly why the defense against Q-Day, called post quantum cryptography, is already being built and rolled out years before the actual quantum computer that would need it exists. Data that has to stay secret for decades, government records, medical histories, trade secrets, is the most exposed, since it needs to survive long enough for Q-Day to become a real threat rather than a hypothetical one. Waiting until quantum computers are actually powerful enough to break encryption would mean waiting until it is already too late for anything harvested along the way

What Is Q-Day? Quantum Computing and Cyber Risk - Palo Alto Networkswww.paloaltonetworks.com