A quantum computer is any device that uses the principles of superpositions of states and entanglement. It depends on quantum bits or qubits to perform mathematical calculation to store and manipulate information. The computational power is determined by how many qubits a machine can simultaneously leverage, as well as how it is able to process information and a vast number of calculations in parallel. Quantum communications are authenticated and can be used to replace classical digital signatures and to encrypt communication networks.
Encryption and decryption methods in cryptographic model are based on the generation of Public and Private Keys come from a sequence of random numbers. Depending on the algorithms the range of this number is from 128 to 3076 bits, which is difficult to share and computationally very expensive to process.
Cryptographic hash, estimation of difficulty, target generation, and nonce number creation by miner, Merkle root, establishing correlation, and execution of consensus algorithm, and complete the proof of work (POW) in blockchain are based on the solving of repeated mathematical and statistical functions. Such functions are used to both generate digital footprint and validate transactions on the ledger. The asymmetric public-key cryptography is the backbone of blockchain security and strength of this key also depends on the randomness of this number. Solving those functions and generation of complete randomness is considered impossible with only classical means due to computational overload.
However, quantum theory can easily be exploited to generate true random numbers, which leads to it being the most imminent threat to blockchain as it can break this public-key based encryption and crack the digital signatures, hence, impact on unchangeable data, unalterable and security, making blockchain as highly vulnerable..
The rapid revolution of quantum computing has rendered the traditional process to generate random numbers no longer be sophisticated enough to formulate cryptographic algorithms. Fortunately, quantum computing offers opportunities to enhance the security and performance of blockchains. We are at the edge of incorporating quantum computational theory to generate large and true random numbers to model our cryptographic algorithms for blockchain based on qubits entangle in spatial and temporal domains.