Tuesday, October 6, 2020

A Note On Blockchains

Blockchains have three components, a data structure, a set of replicas, and a consensus mechanism:
  • The data structure is often said to provide immutability or to be tamper-proof, but this is wrong. It is made out of bits, and bits can be changed or destroyed. What it actually provides is tamper-evidence, revealing that the data structure has changed.
  • If an unauthorized change to the data structure is detected the damage must be repaired. So there must be multiple replicas of the data structure to allow an undamaged replica to be copied to the damaged replica.
  • The role of the consensus mechanism is to authorize changes to the data structure, and prevent unauthorized changes. A change is authorized if the consensus of the replicas agrees to it.
Below the fold, some details.