Ouroboros is a family of

proof-of-stake Proof-of-stake (PoS) protocols are a class of consensus mechanisms for blockchain A blockchain is a type of distributed ledger technology (DLT) that consists of growing lists of records, called ''blocks'', that are securely linked togethe ...

consensus protocols used in the Cardano and Polkadot

blockchains A blockchain is a type of distributed ledger technology (DLT) that consists of growing lists of records, called ''blocks'', that are securely linked together using cryptography. Each block contains a cryptographic hash of the previous block, ...

. It can run both permissionless and permissioned blockchains. Ouroboros was published as "the first provable secure PoS consensus protocol". It was postulated by an academic team led by

Aggelos Kiayias Aggelos Kiayias ( el, Άγγελος Κιαγιάς) Fellowship of the Royal Society of Edinburgh, FRSE is a Greeks, Greek cryptographer and computer scientist, currently a professor at the University of Edinburgh and the Chief Science Officer a ...

at the Annual International Cryptology Conference in 2017. Later that year, Ouroboros (Classic) was implemented by IOHK as the basis of the Cardano blockchain platform and various upgrades. Ouroboros versions include: * Ouroboros BFT was an interim version used in 2020 to enable the switch between the Classic and Praos versions of Cardano using a hard fork combinator that preserved the blockchain history; * Ouroboros Praos (2017) provided security against fully-adaptive corruption in the semi-synchronous model. In 2020, this version was used to introduce decentralized block production on Cardano by stake pools; * Ouroboros Genesis (2018) provides security with a dynamic participation model; * Ouroboros Chronos (2019) is independent of global time; * Ouroboros Crypsinous (2019) gives higher levels of privacy. Cardano's founder

Charles Hoskinson Charles Hoskinson is an American entrepreneur who is a co-founder of the blockchain engineering company Input Output Global, Inc. (formerly IOHK), and the Cardano blockchain platform, and was a co-founder of the Ethereum blockchain platform. E ...

has described the Ouroboros consensus mechanism as energy efficient. Nguyen et al. compared Ouroboros to other PoS protocols. The cryptocurrency Polkadot uses an adapted form of Ouroboros called Blind Assignment for Blockchain Extension.
Kiayias home page at University of Edinburgh

References

External links

Ouroboros
at Cardano Foundation {{Authority control Digital currencies