The cryptographic security of distributed ledgers are the major selling point of blockchain and its apps. Under typical circumstances, these ledgers are basically unbreakable. However, a big shift in technology could lead to an increased vulnerability and threat level that are not currently considered in this design. Many people are starting to ask when the threat level could change.
Physicists have been working toward building an operational quantum computer. People wonder if this could be the threat that has been anticipated against blockchain technology. A quantum computer is a device that uses the principles of quantum mechanics in its calculations. This is instead of binary systems that current computers use. Quantum mechanics use bits or qubits that can be a 0 and a 1 at the same time. Binary is either 0 or 1. Quantum mechanics allows devices to perform some tasks faster than the binary system.
Another feature of quantum computing is entanglement. Paired qubits can be entangled, which grows the device's computing power by an exponential level. This state is difficult to achieve. Physicists currently use lasers and microwaves as well as other techniques to achieve this entanglement. Entanglement also causes a lot of errors.
In blockchain, security is critical. Quantum computing puts it at risk. A quantum computer could run algorithms faster than any known supercomputer. For example, they could use Shor's algorithm for factor decomposition, which would foil most of today's encryption techniques. Some Russian researchers found some risks in blockchain security's one-way mathematical functions. A criminal with a functioning quantum computer could calculate those one-way functions in reverse, allowing them to falsify signatures and gain access to the accounts of other users.
The Russian researchers also suggested that a criminal with a quantum computer could manipulate prices. They suggested that blockchain architects start taking immediate precautions. One precaution could be replacing digital signatures with cryptography that resists quantum attacks. Another technique relies on the use of a quantum internet for wireless communications, but that is many decades away at this point in time. The point is that quantum computing could change blockchain sooner than later.