Casper is an implementation of proof of stake consensus algorithm in development for the Ethereum platform. Proof of stake is an alternative consensus method to the proof of work algorithm commonly used in many blockchain projects such as Bitcoin. In proof of stake, block creators are pseudorandomly chosen from a pool of validators based on the amount of coins they stake — this is sometimes referred to as virtual mining. Casper is the Ethereum foundation's proof of stake implementation. Among other design features, it is designed to solve the nothing-at-stake problem by requiring validators to offer a stake of their coins which can then be slashed under specific protocol conditions whereby the network determines malicious action by that validator.
Casper FFG and Casper-GHOST-CBC
There are two separate implementations of Casper in development: Casper the Friendly finality Gadget (FFG), and casper the Friendly GHOST: Correct-by-Construction.
Nothing at stake problem and Slasher
Naive proof of stake algorithms suffer from the nothing at stake problem. The nothing at stake problem is characterized by the incentive for network participants to contribute blocks to every potential blockchain fork to ensure they receive a block reward on the winning chain. This can result in what is known as a consensus failure; the network does not converge on a single canonical blockchain even without a malicious attacker. Casper implements a design strategy to counteract this problem called Slasher.
The stake slashing and rewards are performed by the protocol. If a bonded validator produces a valid block for the main chain they receive the block reward. Bonded validators who produce blocks on chains which do not end up in the main chain have their bonded stake slashed and lose their deposit equal to the block reward.
The Rchain foundation is implementing a variation of Ethereum's casper implementation. Instead of staking on blocks, Rchain's capser design relies on staking logical propositions.
Consensus Compare: Casper vs. Tendermint
Ethereum Casper 101
Ethereum’s Proof of Stake Casper Testnet Nears Launch
Proof of Stake FAQ
Slasher: A Punitive Proof-of-Stake Algorithm
The History of Casper -- Part 1
Where's Casper? Inside Ethereum's Race to Reinvent its Blockchain
Documentaries, videos and podcasts
- Proof-of-stakeProof-of-stake (PoS) is a system by which a network (e.g., a cryptocurrency blockchain) aims to achieve distributed consensus.
- Vlad ZamfirA developer and blockchain architect at Ethereum.
- Vitalik ButerinRussian-Canadian computer scientist, programmer, writer and founder of Ethereum.
- Greg Lucius MeredithA mathematician and software engineer, creator of RChain.
- Rchain (cryptocurrency)Rchain is a blockchain platform developing a language for smart contracts called Rohlang.
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