None of them exist.
|Unicorn by James Bowe|
This article over at ZDNet was responsible for sending me down this rabbit hole, though I've been rolling my eyes at "Uncrackable Quantum Encryption" articles for at least a decade.
First off, most of the "uncrackable quantum encryption" claims refer to encrypting data for transmitting across networks, between endpoints. The idea is that you can make a tamper-evident system due to the nature of quantum mechanics. If an attacker attempts to manipulate or observe data in a quantum system, the data will be altered. Once altered, we're aware of the attacker and can take countermeasures.
It is more likely that companies and researchers trying to sell the idea of quantum encryption are depending on its Sci-Fi "WOW" factor to sell it as the next big thing in cryptography. In reality there are many issues with quantum cryptography.
1. It is new, and largely untested
When someone claims something is uncrackable, and there are very few people with the knowledge and skills to test that theory, beware. In fact, in the last decade, quantum cryptography has been touted as "uncrackable" many times, and has been cracked just as many times. In fact, somewhat unfortunately, one of the researchers credited with cracking commercial quantum cryptography for the first time is now making this latest "uncrackable" claim!
2. We already have uncrackable encryption...
...Or near enough that the difference doesn't matter in the real world. AES has faithfully served us for over a decade now, and no practical method to crack AES-encrypted data at rest, much less in transit (when used as a stream cipher), has been presented. For any and all practical purposes, AES has fit the bill, so what do we need quantum encryption for?
3. The real problem in most encryption failures is poor implementation
Say someone does come up with a truly uncrackable quantum encryption. Historically, the human factor has been the limiting factor more than the quality of the cryptography. Someone will set it up, configure it or code it incorrectly. Why go through the wall when you can go around it?
4. Aside from researchers, no one is attacking cryptography
Users are the weak point. The person behind the desk and their phone/laptop/desktop is the goal of most attackers, because it is the weakest link, and it works. Even at the server/enterprise level, the low-hanging fruit is code thrown together at the last minute by an overworked developer, not some $200k quantum cryptography endpoint.
Show me some uncrackable quantum encryption that keeps your data safe, and I'll show you the treadmill I use to power my house. He never gets tired.
UPDATE: I noticed the commenters on the ZDNet article that inspired this post state almost all of the same points I make here, which tells me two things: 1) you guys already know better and 2) nobody's buying into quantum BS.