How quantum computers will destroy and (maybe) save cryptography

Quantum computer advances mean we might have only a few years before they can break all public key encryption. The day when every secret is known is near.


More than a decade ago, I was giving an introductory presentation on quantum cryptography, as I had done many times before. I discussed the basic concepts of quantum physics, quantum computers, and quantum cryptography. I ended it with the promise that when quantum computing went mainstream that most of our current digital encryption secrets, which rely on hard-to-solve large prime-number equations, would be immediately revealed to the world.

Most secrets have been protected with some form of asymmetric encryption ever since Whitfield Diffie, Mark Hellman and Ralph Merkle publicly revealed the concept in 1976 in their seminal paper called New Directions in Cryptography. Think RSA, SSL, TLS and HTTPS. We’re talking most websites, digitally signed downloads, online financial transactions, your VPN, smartcards, and most wireless networks—all capable of being broken an instant.

Modern day secure communications rely on the fact that traditional digital computers cannot easily factor multi-factor equations involving large prime numbers. If a computer could do that, and quantum computers can, then it would be game over for any secrets encrypted by that protection.

It’s been theorized that most of the world’s major nation-states have been recording and storing much of the world’s encrypted network traffic for future decryption, just waiting for that day of reckoning to come. America will be able to read Russia’s and China’s top-secret communications and vice-versa. I wrote about this threat nearly eight years ago in a column.

Back to my talk many years ago: When I took questions at the end of the presentation, I was asked how long I thought it would be until quantum computers would be good enough to break all those secrets. I said “10 years. Most quantum physics experts think it’s only 10 years off.”  As I walked off stage, industry luminary Bruce Schneier was walking on to follow me. He casually said to me as he walked on by without breaking stride, “How long have you been saying 10 years?”

I had probably been saying 10 years as the answer for at least 10 years. Bruce made me realize that none of us really knew the answer. The running joke in quantum physics circles is that quantum computers are always 10 years off.

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