Blockchain
A distributed, decentralized digital ledger that records transactions across many computers in such a way that the records cannot be altered retroactively without the consensus of the network. Each block contains a cryptographic hash of the previous block, creating an immutable chain.
Examples
- Bitcoin's ledger records every BTC transaction ever made, permanently and publicly.
- Ethereum's blockchain stores both transactions and smart contract state.
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Related Terms
Consensus Mechanism
The algorithmic process by which a distributed blockchain network agrees on a single version of the ledger. Consensus mechanisms solve the problems of agreement (all honest nodes agree) and Sybil resistance (preventing fake identity takeovers).
Immutability
The property of blockchain data being permanent and unalterable once confirmed. Changing a past block would require re-mining that block and all subsequent blocks with majority network consensus — practically impossible on well-secured networks.
Layer 2 (L2)
A secondary protocol or network built on top of a base blockchain (Layer 1) to improve scalability and reduce transaction costs. L2 networks process transactions off-chain or in batches, then settle final results on the Layer 1 chain for security.
Proof of Stake (PoS)
A consensus mechanism where validators lock up (stake) cryptocurrency as collateral. The network selects validators to propose blocks based on their stake. Dishonest validators risk having their stake slashed. PoS is far more energy-efficient than PoW.
Proof of Work (PoW)
A consensus mechanism where network participants (miners) compete to solve computationally difficult cryptographic puzzles. The first to find a valid solution earns the right to propose the next block and receives a reward. PoW secures the network by making attacks computationally expensive.
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