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# Ouroboros: A Provably Secure Proof-of-Stake Blockchain Protocol

> Ouroboros is a family of Proof-of-Stake (PoS) consensus protocols designed to be provably secure, offering a rigorous cryptographic foundation for blockchain op

# Ouroboros: A Provably Secure Proof-of-Stake Blockchain Protocol

Ouroboros is a family of Proof-of-Stake (PoS) consensus protocols designed to be provably secure, offering a rigorous cryptographic foundation for blockchain op

## Abstract

Ouroboros is a family of Proof-of-Stake (PoS) consensus protocols designed to be provably secure, offering a rigorous cryptographic foundation for blockchain operation. The protocol achieves consensus by dividing time into epochs, each composed of several slots, where a slot leader is pseudo-randomly elected for each slot. This leader is responsible for producing a block if one is not already available. The security of Ouroboros relies on the assumption that less than half of the total stake is controlled by malicious actors. The paper presents formal proofs demonstrating its security against various attack vectors, including dynamic stake manipulation and network adversaries. Ouroboros variants address different network conditions, such as synchronous and asynchronous settings, and offer guarantees of safety and liveness. Its development marked a significant step towards establishing the cryptographic rigor expected for production-grade PoS consensus mechanisms in the blockchain space.

**Authors:** Aggelos Kiayias, Alexander Russell, Bernardo David, Roman Oliynykov

**Publication:** IACR ePrint Archive

**Publication date:** 2017-01-01

## Key findings

* Ouroboros provides a provably secure Proof-of-Stake consensus protocol.
* It divides time into epochs and slots, with slot leaders pseudo-randomly elected based on stake.
* Security is maintained under the assumption that less than 50% of the stake is compromised.
* Formal cryptographic proofs are provided to demonstrate safety and liveness properties against adversaries.

## Citation

Aggelos Kiayias, Alexander Russell, Bernardo David, Roman Oliynykov (2017). Ouroboros: A Provably Secure Proof-of-Stake Blockchain Protocol. IACR ePrint Archive. [https://eprint.iacr.org/2016/889](https://eprint.iacr.org/2016/889)

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**Canonical knowledge ID:** `research:ouroboros-a-provably-secure-proof-of-stake-blockchain-protocol`