Spy agencies are already stockpiling encrypted data to unlock later once quantum computers arrive, a slow-moving risk to banks, power grids, and anyone who assumed their secrets stay secret.

• Experts put the odds at roughly one in four to one in three that a machine able to break today's encryption exists by 2034.
• The bigger problem is "steal now, decrypt later" — data copied today can be opened years from now, and you can't take it back.
• A break would hit money first: banks could no longer verify transfers, and one large US bank losing access for a day was modeled at trillions in damage and a six-month recession.
• New quantum-proof encryption standards exist and Google, Apple, Amazon and Signal have switched, but rewiring every bank, meter, and pacemaker could cost over $1 trillion.
• China is skipping the software fix and building satellite and fiber networks that protect keys with physics — security only rich countries can afford.

Outlook: Expect a long, uneven upgrade where big tech and governments move first and billions of small devices keep running on locks everyone knows will eventually fail.