Nov 10,2018
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Journalists regularly report on the danger quantum computers are supposed to pose to Bitcoin and many other crypto currencies. But how dramatic is this threat really?

A look into the virtual forest shows that quantum computers are represented as a threat to Bitcoin formula and other crypto currencies like this: https://www.onlinebetrug.net/en/bitcoin-formula/. Whenever updates to the current development status are displayed, the respective authors point out what this development would mean for encryptions.

The image is dystopic: All encryptions can fall victim to the quantum computer, our accounts and thus our privacy are at the mercy of the theft by anonymous hackers or the NSA. In view of the threat to RSA encryption, this may even be true.

Recently, this fear has been associated with the trend towards crypto currencies: Bitcoin would be finished with quantum computers, the wallets could be emptied and the whole system would go down – some circles represent Cryptogeddon in some way or other.

The concern is not entirely unfounded and has led to various projects already using encryption algorithms that are quantum resistant. So they promise that wallets are unhackable even for quantum computers.

In this respect, it is understandable that many Bitcoin investors wonder why Bitcoin does not become active. In order to answer this question, this article will assess the risk that quantum computers pose to Bitcoin.

In order to assess the danger of quantum computers correctly, it is important to understand the possibilities and limitations of quantum computers. First of all, the article would like to outline what a quantum computer is.

Classical computers are digital computers that process information about zeros and ones. A bit can be either 0 or 1. More complex information is realized by more bits, processing them by logical circuits. For example, an AND circuit results in a 1 only if a 1 is sent via both inputs. For an AND connection there are four possible combinations, which in the worst case all have to be calculated in order to get to 1:

0 AND 0 results in 0

1 AND 0 results in 0

0 AND 1 results in 0

1 AND 1 results in 1

A quantum computer stores information in so-called qubits. These make use of phenomena of quantum mechanics. Some readers will know the thought experiment “SchrÃ¶dinger’s cat”: A psychopath locks a cat in a box into which he has placed a capsule of prussic acid that opens by chance. If it opens, the cat dies. As long as the box is not opened, the cat can be described as dead and alive at the same time. Transferred to qubits, this means that they cannot be described as 0 or 1, but as 0 and 1 at the same time. One can imagine accordingly that in a similar process as the above AND-linking not several processes must be calculated through, but all are calculated at the same time.

What kind of attacks are possible with quantum computers?

As far as the above is concerned, it is understandable that quantum computers can therefore dramatically reduce the runtime of algorithms. And this is not purely speculative: even without quantum computers, scientists have already developed algorithms that have a certain relevance for the security of Bitcoin. The Shor algorithm aims to factorize large numbers, which is relevant for many cryptographic processes. For example, RSA is based on the fact that factorization methods have an extremely long runtime – and are therefore indirectly endangered by quantum computers.

In addition to the Shor algorithm, the Grover algorithm is also known: This is about searching within an unsorted database or inverting a function. The Grover algorithm thus allows to calculate the x for a given y for a function f(x) = y. Since f(x) can be an encryption or hashing function, this algorithm is also a danger for different cryptographic functions.

What is the current state of quantum computers?

According to her, various companies and institutions have already developed quantum computers. The company D-Wave Systems is said to have developed four computers in the meantime. D-Wave 2000Q should work with a total of 2048 Qubits. However, one can hear various critical voices that question the properties advertised by D-Wave Systems. According to Edward Snowden, NSA will also work on a quantum computer focused on cryptography. As na