If you were to do a quick search on the Internet about "quantum computers" and "encryption" you're likely to pull up a ton of articles, many of which say that our current method of encryption is doomed by quantum computers. What is this all this about? Is it true? Is there an imminent danger lurking around the corner?
There are several technologies at play here. Let's see if we can sort through them to make some sense of it all.
Today inside a computer everything is represented by either a 0 or a 1. However, the development of a completely different type of computer has been underway for some time now. It's called a quantum computer. Quantum computing relies on atomic-scale units (qubits) that can - wait for it - be both 0 and 1 at the same time (try to wrap your head around that). This makes it possible for one qubit to carry out two separate streams of calculations at the same time. The end result is that quantum computers will be far more efficient than today's computers.
So, what's the big deal? Isn't it good that we'll have faster computers in the future?
Yes, it is good. But there's a downside, too. Due to the speed and efficiency of quantum computers, they could easily break how we do encryption--and that would not be good. Remember that encryption is one of the pillars of security, guarding everything from your online shopping at Amazon to government secrets to, well, you name it.
Most encryption that we use today is called asymmetric cryptographic algorithms, also known as public key cryptography. Asymmetric encryption uses two keys instead of only one. These keys are mathematically related and are known as the public key and the private key. The public key is known to everyone and can be freely distributed, while the private key is known only to the individual to whom it belongs. When Bob wants to send a secure message to Alice, he uses Alice's public key to encrypt the message. Alice then uses her private key to decrypt it.
Public key cryptography starts by multiplying two prime numbers (a prime number is a number divisible only by itself and 1). What makes our encryption so good is that it's really hard to figure out the prime numbers that make up a value (called factoring), even for today's computers.
Back to quantum computing. A single quantum computer could crack encryption by using hundreds of atoms in parallel to quickly factor huge numbers. And to break encryption would not be good.
When will this happen?
While some people think this will occur very soon (ten years from now), most security professionals think it's farther out in the future before we have quantum computers cracking encryption, maybe 30 years or more. Currently there are new encryption proposals being evaluated that are quantum-safe that could not be broken by quantum computers, so work is underway to prevent this from happening.
But what is often overlooked in this discussion is the simple fact that if we use larger numbers with today's encryption, such as increasing the length of the "key" from 1,024 bits to 7,680 bits or larger, it will make the encryption safe even from quantum computers (they have a tough time with really large numbers). Using longer keys is something that can be easily implemented right now; we just have to get busy doing that.
So, when you see these articles about quantum computers destroying encryption just remember that it's fairly unlikely there will be a great catastrophe ahead.
(Thanks to Ted Simpson for the suggestion on this topic)
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