Quantum computing is the technology set to solve intractable problems that cannot be handled by the currently available computers. Actually these computers will be more than a million times faster than the classical computers and will not be restricted to solving a problem at a time as they come with multi-tasking abilities.

Their energy requirement is much less and thus not only competitive but also far more superior in most aspects. It is on this background that security experts estimate that quantum computers will break bitcoin security in a period of 10 years.

Bitcoin Blockchain security

To be able to fully appreciate the implication of a quantum computing presence, let us first examine how the blockchain works.

• To create a bitcoin, miners have to first solve a cryptographic puzzle whose answer will connect to the previous block that was mined. This process is referred to as hashing. Every block is unique in that a different hash has to be established in order to be linked to the previous one. This is one of the major security features of the blockchain. To solve a hash equation is so complex and both time and power consuming that it serves as a limitation on the number of miners who would be willing to undertake such a task. That is why miners form pools in order to divide the tasks and share costs.
• Once a hash or specifically the nonce has been worked out and determined, a block is in effect created and gets listed in the distributed ledger for validation. After validation, which takes on average 10 minutes, it is linked to the previous chain hence the term blockchain. Miners commence work to create the next block through the same process of hashing.
• To access the mined bitcoins, another cryptographic feature of Bitcoin has to be applied. This is the feature that ensures that only the rightful owner of a bitcoin can access and spend it. This feature involves the use of a public key, a private key and an elliptic curve signature. To have all these in place, some mathematical encryption schemes have to be unraveled.
• The owner of the bitcoin will generate two keys, usually numbers, which are the:-
• Public key- this is usually visible to the public;
• Private key – only known to self
• It is possible to generate the public key from the private key but totally impossible to generate the private key from the public key. An elliptic curve signature is optional and is normally used to verify the ownership of the private key without actually disposing the details of the private key.

Threats posed by Quantum computers

Quantum and crypto appear to be two competing systems. Let’s analyze how Quantum computers pose a threat to this great technology.

We have mentioned above that the task of mining is so computationally intensive that miners have to pool together to share tasks. There is a danger here in that a group of miners can align themselves to control 50% of the computation power used on the network, giving them monopoly over the control of the ledger. If this group succeeds, they can delete transactions so that they are not linked into the blockchain. This in effect means that miners can double spend a bitcoin by cheating the system and all this would be one without the knowledge of the rest 49%!

Herein lays the threat with the onset of quantum computing that some would take advantage of such an anomaly. If an equally bad-willed owner of a quantum computer uses it to mine bitcoins, with the speed we mentioned of over one million times the speed of traditional computers, how many extra bitcoins would he or she mine?

• We have also seen that only the authentic owner of a bitcoin can spend it and that authenticity is drawn from the ownership of the private key. However, a quantum computer can easily ascertain a private key using the public key by use of computerized calculations. So where is the security with the private key thereafter? Quite a threat to reckon with.
• The elliptic curve signature which serves as an additional security measure to establish the authentic ownership can easily and completely be broken by the use of quantum computers. Actually, Diresh Aggarwal, a computer expert at National University of Singapore, says that this will be a done deal by year 2027 which is less than 10 years away.

Way forward

Having established that quantum computers are indeed a threat to bitcoin technology and all cryptography for that matter, it is consoling to know that there are people working round the clock to avert or minimally reduce the consequential eventualities. Some of the steps being taken and considered include:-

• Introduce stringent regulation on the minimum control of computational power a group of miners can possess. That way, there can be no veto power over fraudulent dealings.
• Enhanced ASIC computers. Miners use specialized ASIC computers. If the manufacturing companies can improve on them, they can become more resistant to the speeds offered by quantum computers even though this would only prolong the period but not completely avoid the takeover.
• It is possible to create public key software that is resistant to invasion by the quantum computers.
• Still on public keys, one can prohibit a quantum user intruder from deriving your private key through the public key as earlier mentioned by always generating a new address with every transaction. That way you will cheat the quantum system with the confusion that ensues.

In conclusion, quantum computers are a real threat to Bitcoin and all crypto systems. However, with proper preparation, bitcoin might come through with minimal bruises from the attacks considering there is substantial time before quantum computers can be built to perform the said threats. Currently, there is a pilot testing expected to be launched any time this year though far from the final intended product. As the saying goes, to be forewarned is to be forearmed.