Quantum computing vs blockchain technology

How is quantum computing a threat to blockchain technology?

My crude understanding of blockchain (derived mainly from the Wikipedia article) is that it gets its security from two sources:

  • Individual communications are performed using a public key cryptography scheme
  • Information is stored in a decentralised manner across many different computers, meaning that there are many different copies of the same information.

The level of security provided by these two items differs, I suspect. Public key cryptography has an exponential form of security against classical attacks: it’s based on a mathematical problem, and you add one bit to the problem size, and the difficulty (roughly) doubles. It’s really easy to add a few bits, and put the problem completely out of anybody’s reach. Meanwhile, for the decentralised part, I imagine that adding one extra computer to the network doesn’t significantly increase the resources required to monitor all the communications; for a network of NN nodes, there are only (N2)(N2)communication links to monitor (a polynomial in NN, not exponential). So, while adding a few more computers to the network might make monitoring a daunting task for an individual, state-level interference is unlikely to be eliminated. Thus, the security is heavily dependent upon the security of the public key cryptosystem being used. ..Read More..


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