They say that public key infrastructure or PKI uses very complex encryption. What if that encryption breaks one day when quantum computers complete? What if they decrypt all private messages and data? What will be the replacement then?

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    PKI is not the problem in your scenario. The algorithms used to encrypt are the problem.
    – schroeder
    Mar 10, 2019 at 15:28
  • This question is not a great fit for a Q&A format. It requires speculaton about the future and future technologies.
    – schroeder
    Mar 10, 2019 at 15:29
  • If you search by the tag [quantum-computing] you will see a lot of questions with focus on different aspects of your question.
    – schroeder
    Mar 10, 2019 at 15:54
  • @schroeder , it’s a fine question. If X509 couldn’t accommodate change, that would be a problem, but it’s not like this hasn’t happened before. Mar 10, 2019 at 15:55
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    I have edited as per John's comments. I think this is what is being asked. Hefaz - please read up on the definitions you are unsure of (algorithms, protocols, standards, certificates, processes, agreements, contracts, management packages, keys, committees, etc) - all available on Wikipedia
    – Rory Alsop
    Mar 12, 2019 at 18:40

1 Answer 1


Quantum computing is being developed to attack specific algorithms. Right now there are efforts under way to find algorithms that are resistant to quantum computing attacks. Such algorithms are called post-quantum.

The Public Key Infrastructure is built on the concept of certificates, not algorithms. Certificates are documents that are capable of storing many types of signatures using many different algorithms. If one algorithm falls, such as happened when MD5 was found to have weaknesses allowing the forging of certificates, we can stop using it and switch to another.

Researchers give us warnings as they close in on weaknesses. An example of this happened a couple of years ago when SHA-1 fell to an attack. Even though there was no immediately apparent vulnerability to certificates, people stopped trusting SHA-1 signatures on certificates, and switched to alternatives.

As quantum computing approaches the capability of cracking a specific algorithm such as RSA, the world will switch certificates to trusting only post-quantum algorithms. PKIs will continue.

Throughout history, cryptography has always been a game of cat and mouse. The ability to modify keys, algorithms, and protocols has always been critical to maintaining security. Quantum computing may be a threat, but not necessarily a game ender.

  • So only by changing the algorithms of those certificates, even after completing the quantum computing (if it's not completed in the lab already) we can use PKIs? Can quantum computing suggest something different then, instead of PKIs?
    – Hefaz
    Mar 10, 2019 at 18:10
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    You seem to think PKI is a single thing like a box that’s plugged into a wall, or a program people run. PKI is the name for the collection of algorithms, protocols, standards, certificates, processes, agreements, contracts, management packages, keys, committees, etc., that all come together to enable the encryption of web traffic. If any part of it needs to be replaced, it can be - slowly, to be sure - but it can all be fixed. Mar 10, 2019 at 18:23
  • The fact is that I cannot explain the question since some of the above (algorithms, protocols, standards, certificates, processes, agreements, contracts, management packages, keys, committees, etc) are unclear to me somehow. I will ask it once again, but this time I might seem more stupid, or you will get the question. Will the entire process of the PKI one day come to an end, so that we can use something different? think of something without public and private keys.
    – Hefaz
    Mar 10, 2019 at 18:38
  • PKI is the name of the infrastructure based on public keys. Like anything, it’s impossible to predict the future. Some want to replace trusted root CAs with a web of trust model (although that has some serious operational problems.) But it’s still a way to get keys exchanged , so it could still be considered a PKI. Mar 10, 2019 at 19:35
  • If we are going to use cryptography, we have to have a trustable way to securely exchange keys. If we outlaw encryption there’d be no need for it. But we’d also then have no way to conduct business. Pre-exchanging secret keys with every retailer and web site simply isn’t practical nor scalable. So public key cryptography is here for the foreseeable future, and that implies a PKI of some sort must exist to serve it. Mar 10, 2019 at 19:41

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