back to article Quantum Key Distribution: Is it as secure as claimed and what can it offer the enterprise?

Do the laws of physics trump mathematical complexity, or is Quantum Key Distribution (QKD) nothing more than 21st-century enterprise encryption snake oil? The number of QKD news headlines that have included unhackable, uncrackable or unbreakable could certainly lead you towards the former conclusion. However, we at The Reg are …

  1. Pascal Monett Silver badge

    "magic quantum woo-woo security"

    I think we're going to be getting a lot more of that before we start seeing any actual quantum encryption security.

    And the biggest problem for me is the fact that it seems you can only reliably exchange keys over a dedicated fiber line, without interruptions. Well that means that quantum encryption over the Internet is off the cards, in which case quantum encryption is going to remain a niche application in locations that already likely have more security than you can imagine.

    1. Claptrap314 Silver badge

      Re: "magic quantum woo-woo security"

      You mean like running a cable down an oil pipeline to allow command and control of the system independent of the internet?

      Oops. We already know--no money to spend on such a thing.

    2. bazza Silver badge

      Re: "magic quantum woo-woo security"

      It has been done through the atmosphere, though I'd hesitate to say that it had been made reliable (I don't know).

  2. 2+2=5 Silver badge

    Asking a company whether they can benefit from quantum <anything> is like...

    Asking a company whether they can benefit from QKD or quantum <anything> is like asking them whether they can benefit from fusion power ... a practical working system is so far in the future it's impossible to answer on anything more than a hypothetical basis.

    1. bazza Silver badge

      Re: Asking a company whether they can benefit from quantum <anything> is like...

      Er, the semiconductor junctions used to make up the chips that are in the computer you used to type that comment rely entirely on the quantum behaviour of selectively doped silicon.

      We've all benefitted enormously from a quantum something.

      1. Blazde

        Re: Asking a company whether they can benefit from quantum <anything> is like...

        The first rule of sweeping statements: They're always wrong.

        Quantum Healing is another quantum something that's not even a bit like fusion power.

  3. Sitaram Chamarty

    my "QKD for managers"

    Here's what I say when a "manager" asks me about QKD:

    QKD is a popular and well known method of extracting money from gullible people -- whether it is in the form of grants, startup funding, or outright "product" purchase. In keeping with "quantum" principles, the person being diddled out of his money cannot simultaneously also *know* that he's being diddled.

    More seriously, here's some excellent reading for anyone thinking QKD is actually useful:

    1. Paul Kinsler Silver badge

      Re: QKD *is* a popular

      You are confusing "is" with "is used as".

    2. Paul Uszak

      Re: my "QKD for managers"

      And perhaps a more balanced answer:

      Reiterating: The fundamental point is that you need to keep implementation distinct from protocol. AES-GCM is also pretty weak if the key is on a Post-it stuck to the monitor. As is RSA/DH if the random number generator is weak/subverted. Everyone should just calm down.

      Mine's the one time pad over there...

      1. Sitaram Chamarty

        Re: my "QKD for managers"

        good article, but interception is not the only problem. With sufficient hardware resources, Eve can implement a true MITM -- get between them and relay messages back and forth -- because QKD has no *identity* component.

        1. Paul Uszak

          Re: my "QKD for managers"

          Oh dear. You've gotten the concept upside down. Interception is irrelevant. The beauty of QKD is that it is ALL about identity. The identity management comes from the Observer Effect of quantum physics. Any photon that is observed changes state. That's fundamental to the Universe, and exempt from any hardware resource considerations.

          A "true MITM" relay would introduce measurable bases errors at the rate of an additional 50%. When Alice and Bob compare their expected results, the attack is detected. That is QKD's raison d'etre. The original BB84 article is here:

          And that's why everyone is getting QKDNs.

  4. elsergiovolador Silver badge

    New world

    We are slowly entering the world where even the research of encryption methods will be illegal.

    Companies that use VPN will be force to log all traffic, who connects to what and when.

    You won't even be able to communicate in a foreign language that is not on the list.

    SSL? You'll have to share private keys with your provider so they can insert government taps.

    EU is already pushing for monitoring of private chats.

    In 10 years, you'll have to prove that what you say is not a disguised encrypted message. Maybe we will have to wear a speech monitoring device, these could be embedded in mandatory masks.

    In 25 years we will get an implant monitoring our thoughts and sending your vitals. Thinking about protesting? Bam, implant will release a sedative and dispatch the thought police.

    1. Throatwarbler Mangrove Silver badge

      Re: New world

      Ok, doomer.


        Re: New world

        Ok, warbler.

      2. bombastic bob Silver badge
        Thumb Up

        Re: New world

        heh heh heh

  5. amanfromMars 1 Silver badge

    Is this what you begin with, or end up with?

    In other words, it's all well and good having a perfected quantum protocol, but if someone can do memory analysis on A or B's systems, then your "super secure" key can get pwned. "It's monumentally naive in my view that the companies producing QKD tech don't take this head on," Dr Carney concludes. "Hiding behind 'magic quantum woo-woo security' is only going to go so far before people start realising."

    That is as may be, however pwnage is absolutely useless until there is any remote attempt to try take unofficial private and/or pirate advantage of quantum key secured information, and then, as is the recognised nature of perfect quantum protocols, will the information and advantage be immediately changed by key quantum communication partners to render the raiders persons of interest to correctional offices/special forces in service of key quantum security requirements.

    It is naive in the extreme to not recognise that sort of interference probing QKD tech for undeclared and inequitable advantage as catastrophically self-isolating and highlighting and designedly [by QKD technology buffers] self-destructive.

  6. sebacoustic

    offtopic, sorry

    > we at The Reg are unrelenting sceptics

    Thankfully having quietly put aside the "climate-skeptic" rhetoric after it became patently clear you were siding with the morons...

  7. Paul Uszak

    Abe Lincoln knew the truth about QKD.

    He's attributed to have said "You can fool all the people some of the time and some of the people all the time, but you cannot fool all the people all the time."

    But that's exactly what quantum deniers (QD) are espousing. Any relation to QA? The banks, the governments (, the universities, the militaries, Europe ( are all going for QKDNs because they're secure when correctly implemented. They allow mathematically unbreakable one time pads to be distributed and used.

    But of course they're all fools. We here know the truth, eh?

    1. IGotOut Silver badge

      Re: Abe Lincoln knew the truth about QKD.

      The same militarys that bought bomb detector wands? Or Universities that get scammed over and over again? Sane for goverments (covid payments anyone?

      Being big and having money doesn't make you smart.

    2. Blazde

      Re: Abe Lincoln knew the truth about QKD.

      "[Federated Quantum System] initiative, which includes companies from each country to design and test the system."

      Jobs + tax revenues for all. They're definitely no fools.

      "[EuroQCI] agreement is worth several millions of euros"

      Behold the shear scale of resources the world's foremost supranational economy is capable of bringing to bear on such critical technology. I hear Dr. Evil was overjoyed to be chosen to head up the project.

      1. Paul Uszak

        Re: Abe Lincoln knew the truth about QKD.

        Please don't conflate a self-serving political system and the industrial-military complex with a cryptographic protocol. The article was about the protocol. This is why these threads go off the rails.

        If you have insight into how QKD is cryptographically flawed that the organisations I listed don't, please put up. Mathematical detail would be a bonus :-)

        1. Blazde

          Re: Abe Lincoln knew the truth about QKD.

          "Please don't conflate a self-serving political system and the industrial-military complex with a cryptographic protocol. The article was about the protocol."

          Yup I think you should follow that advice and realise how pointless your original comment was.

          Big organisation investing - for them - miniscule amounts of money into hyped tech proves nothing about the intrinsic value of that tech. It points to them seeing the possibility of some commercial value. At most it indicates they see an outside possibility of some intrinsic value and they don't want to be left behind in case it turns out that way when the cost of keeping up is so low.

          The clearest mathematical detail is that all these organisations already make extensive use of low cost cryptography without any meaningful key distribution issues and no mathematician is up in arms about how insecure all those protocols are.

          It's interesting blue sky research. It doesn't solve any of the many very big current computer security problems.

  8. Arthur the cat Silver badge

    "it's in the implementation where things start to get very sticky"

    In theory, theory and practice are the same; in practice, theory and practice are different.

    1. amanfromMars 1 Silver badge

      Re: "it's in the implementation where things start to get very sticky"

      In theory, theory and practice are the same; in practice, theory and practice are different. ..... Arthur the cat

      And such renders to quantum communications practitioners their stealthy secure decidedly unfair and inequitable overwhelming advantage, Arthur the cat.

      However, one might like to now know, before there be many proposing to be interested for their own personal selfish gain, It is not a failsafe protocol for everyone whenever only needed for an extremely select few into doing great business with an extremely selective few .... who may or may not be considered chosen and exalted because of what they are purported to be able to do ..... and the emerging evidence would support as being honestly true.

      And yes, it's in the implementation where things start to get very sticky and tricky for many who deserve nothing less and a whole lot more besides, with many not able to survive to experience because of their wilful and wanton sinnings in the past and their encouraging stalwart support for such activities in others.

    2. bombastic bob Silver badge

      Re: "it's in the implementation where things start to get very sticky"

      I have to wonder how quantum 'anything' can reliably be implemented without some form of entanglement, especially entanglement that can be established at a distance. Entanglement would solve a LOT of problems, but it may ALSO be the most secure comms method of all.

      I'm always hoping that someone actually did this, and then I see a lot of tap-dancing on the explanation of the hardware, and am once again disappointed.

      Some time ago I studied how to make q-bits and things like that. Using the quantum bits as photons in a fiber optic line is interesting, but from what I see, implementing that idea seems as if it would be riddled with bit errors and missed bits. I have to wonder how sophisticated the error correction algorithm would have to be...

      yeah, the science is STILL too young to be practical, in my bombastic opinion. I want to see it work, but so far, not very practical, it seems.

      1. amanfromMars 1 Silver badge

        Re: "it's in the implementation where things start to get very sticky"

        I have to wonder how quantum 'anything' can reliably be implemented without some form of entanglement, especially entanglement that can be established at a distance. Entanglement would solve a LOT of problems, but it may ALSO be the most secure comms method of all. .... bombastic bob

        Methinks entanglement is both vital and essentially virtually achieved to be universally practical, bombastic bob, and I would agree entanglement would solve a LOT of problems, and for now, .... because who knows what other delights the future will bring, .... be the most secure comms method of all.

        Some would tell you hardware plays only a minor supporting role being as how quantum communications is a proprietary intellectual property exchange/hearts and minds meld which does make physical interference practically impossible.

  9. Anonymous Coward
    Anonymous Coward

    One truism that I believe covers all security is "anything that can be made can also be unmade" and the last usually much more easily.

  10. Anonymous Coward
    Anonymous Coward

    Banks, governments, militaries. Pfft. If the Adult Entertainment Industry decided to use quantum tech to distribute their wares, the whole thing would be sussed-out, working, and in 75% of homes within 5 years.

    1. Anonymous Coward
      Anonymous Coward

      But if the adult industry was involved you know the key pair values would be 36-DD

      Mines the one with the soiled hanky dribbling from the pocket

    2. DiViDeD

      The Adult Entertainment Industry

      A few years ago (OK, quite a few decades ago now - where does it go?) I was in a meeting discussing the possibility of selling product online. It had been decided that we would need to employ a consultancy firm for much dosh to guide us through the process.

      In my youthful innocence (All right - many decades!), I asked why we didn't just get in touch with the webmaster of a porn site because those guys had been doing online payments for years.

      My suggestion wasn't met with the kind of reaction I'd hoped for.

  11. bazza Silver badge

    From the article:

    "On a QKD system, the mathematics is in some way intrinsically, and necessarily, linked to the actual physicality of the system. This situation is unavoidable, and we would do well to design for and around it."

    The thing is, whilst both quantum mechanics and special / general relativity are both theories that have excellent backing from myriad reliable experiments, they do not wholly agree with each other (especially about gravity). What this means with absolute certainty is that one of these theories is incomplete.

    And it might be quantum mechanics that is wrong...

    So, if one accepts that quantum physics genuinely is fully described by our theories of it, but someone else has a better theory that just happens to have a loophole, then QMKD is worse than useless. A lot worse, in fact.

  12. Anonymous Coward
    Anonymous Coward


    The Books we used to think we know, are wholly about quantum mechanics, but does anybody pay attention to quantum steganography?

  13. sreynolds Silver badge

    So the whole point is?

    You cannot prove that the system is quantum except in the case where the key is compromised?

    1. Paul Uszak

      Re: So the whole point is?

      Err, no. The system is quantum as it deals with the generation, transmission and measurement of photon polarizations. The point is (quoting from the BB84 paper,

      "...when information is encoded in non-orthogonal quantum states, such as single photons with polarization directions 0, 45, 90, and 135 degrees, one obtains a communications channel whose transmissions in principle cannot be read or copied reliably by an eaves­dropper ignorant of certain key information used in forming the transmission. The eavesdropper cannot even gain partial information about such a transmission without altering it a random and uncontrollable way likely to be detected by the channel's legiti­mate users. "

      So I can send you 'stuff' with 100% confidence that no one has read it.

      1. stiine Silver badge

        Re: So the whole point is?

        How do we entangle/eavesdrop on every quantum key exchange (ignoring whether we get anything useful out of it) so that there isn't any quantum communication using those keys? Do we just need a soil compactor on the surface above the buried fibers? Do I have to be directly above it or can I be 20m away and still prevent the internet from working properly?

        1. Paul Uszak

          Re: So the whole point is?

          Well I think that you'd have to be in the presence of the fibres. Perhaps you could tie a really tight knot that would choke off the internet. The keys wouldn't be able to get through if the knot radius was less than the diameter of standard cryptographic photons. Or use plumbers' freezing spray to really slow them down.

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