The End of Crypto?

Allow me to explain

Quantum computers are devices with the ability to do many parallel calculations simultaneously by leveraging properties of quantum physics.

The company that builds and maintains them, Dwave Systems, wants to make them accessible to the public through the cloud (https://www.cnbc.com/2018/02/23/d-wave-is-raising-money-to-bring-quantum-computing-to-public-cloud.html).Should they? - With great powe...

Currently, the largest quantum computers is 2000 qubits, it can represent 2^2000 states(which is a lot); it is specialized so it can only carry out some tasks.

At the International Conference on Quantum Technologies (ICQT-2017), Mikhail Lukin announced that his team had successfully created a 51-qubit quantum computer capable of, in theory, executing general computations.(Scary stuff!)

Cryptography relies on the fact that brute force attacks are infeasible.It's difficult, and damn near impossible, to find a p and q where M = p*q for a sufficiently large M in a practical amount of time.Here's a great illustration by 3blue1brown on how secure 256-bit hashes are:

(

)

More time than the universe has existed?

Although the claim above was refuted, it doesn't make any less impressive(The tests were specialized and designed to it's advantage).

In the near future, general purpose quantum computers with sufficient qubits could in theory break modern cryptography (and with it cryptos, through a 51% attack), in seconds rather than billions of years it would currently take.Whop would trust in crypto anymore?

Not all cryptos could be compromised by a 51% attack, others with different algorithms(Proof-of-stake) would probably not be affected. On the other hand, a form of a 51% attack is possible with less than 50% of the network's mining power, but with a lower probability of success.

Has it already happened?

• The mining pool ghash.io briefly exceeded 50% of the network's computing power in July 2014, the did put out a statement promising not to reach 40% of the total mining power in the future.
• Krypton and Shift, two blockchains based on ethereum, suffered 51% attacks in August 2016.
• The tangle(IOTA Blockchain),a third generation blockchain, could be compromised by an attacker through a 34% attack.

Break modern cryptography here:(https://quantumexperience.ng.bluemix.net/qx/experience)

With the advent of quantum computers would this be the norm?Not quite.

Several solutions have been brought forward:

• We could use longer hashes and require larger keys and all would be fine! -so simple,right?
• There are some other encryption standards in the works but generally less disruption is preferred.(https://en.wikipedia.org/wiki/Post-quantum_cryptography)

TL;DR

• Quantum computer are BAD!They can break modern encryption. :(
• The ones in operation are specialized, so nothing to worry about.
• Post quantum computing cryptography would require some change to our systems, though not a radical one.