The parts that matter when the system is yours to run.
- Hash functions and Merkle trees
- A cryptographic hash turns any input into a fixed-size fingerprint; change one bit and the output changes completely. Transactions are hashed in pairs up a Merkle tree, and the single root commits to every one of them, so inclusion can be proven with a short path of hashes. SHA-256 · Keccak-256
- Consensus: PoW vs. PoS
- Proof of work makes rewriting history cost real energy and hardware: nodes follow the valid chain with the most accumulated work. Proof of stake puts capital at risk instead: validators vote with staked collateral and can be slashed for provably dishonest behavior. work · stake
- UTXO vs. account model
- Bitcoin keeps a public set of unspent outputs that are consumed whole and replaced with new ones, including change. Monero also spends outputs, but nobody can see which ones have been spent: one-time key images block double-spends without revealing which output was used. Ethereum keeps a global state of accounts and balances that transactions update in place. inputs → outputs · state → state′
- Mempool and fees
- Valid transactions wait in each node’s own mempool until a block includes them. Block space is scarce, so those building blocks generally favor transactions that pay more per unit of space or gas. sat/vB · gas
- Cryptography
- Bitcoin signs with ECDSA and, since the Taproot upgrade, Schnorr signatures, both over the secp256k1 curve. Monero’s keys, one-time addresses and ring signatures live on edwards25519, a twisted Edwards curve birationally equivalent to Curve25519 (the curve behind Ed25519). secp256k1 · ed25519
- Finality and reorgs
- On proof of work chains, finality is probabilistic: a competing branch with more work can replace recent blocks in a reorg, and each confirmation makes that less likely. Ethereum adds explicit finality: once a block is finalized (about 13 minutes), reverting it would require validators holding at least one-third of all staked ETH to break the protocol’s rules, and that stake gets slashed. confirmations · checkpoints