What is Q-Day?
Currently, internet security (like RSA encryption used in banking and HTTPS) relies on mathematical problems that would take a traditional supercomputer 300 trillion years to solve. A sufficiently powerful Quantum Computer could solve it in minutes. The day this happens is known as 'Q-Day'.
Store Now, Decrypt Later (SNDL)
Hackers (and state-sponsored actors) are currently stealing massive amounts of encrypted data. They can't read it today, but they are storing it. When they acquire a quantum computer in 5 or 10 years, they will decrypt everything instantly.
Post-Quantum Cryptography
Enterprises are not waiting. Organizations like NIST have finalized 'Post-Quantum Cryptography' algorithms. These are new mathematical puzzles that even quantum computers cannot easily solve. Tech giants are currently migrating their infrastructure to these new standards.