Blockchain and Cryptocurrency Security
Stub. How Bitcoin-style blockchains use hash chains and digital signatures to achieve tamper-evidence and ownership without a trusted party, proof-of-work/consensus as the mechanism preventing double-spending, and the security properties (and known attacks — 51%, selfish mining, smart-contract bugs) that follow from this design.
A blockchain is a direct application of two cryptographic primitives already covered — collision-resistant hashing (chaining blocks so tampering with history is detectable) and digital signatures (proving ownership of a coin without a central registrar) — combined with a consensus mechanism (proof-of-work, in Bitcoin’s case) that solves a genuinely new problem: reaching agreement on transaction order among mutually distrusting, permissionless participants, which is what prevents double-spending. Covers this construction and its security assumptions (honest-majority hashpower), plus the attacks that follow from violating them — 51% attacks, selfish mining — and the additional attack surface smart contracts introduce once the blockchain executes arbitrary code. See distributed-consensus-and-paxos for the classical (permissioned, non-Byzantine-incentive) consensus this generalizes.
Outline (TODO — flesh out each)
- Hash chains and tamper-evidence
- Ownership via digital signatures
- Proof-of-work and preventing double-spending
- Security assumptions — honest majority hashpower
- Attacks: 51% attacks, selfish mining
- Smart contracts and their added attack surface