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Glossary

50% disk compression​

A default assumption in Leios cost modelling that estimates storage savings through compression techniques.

Approximate Lower Bound Argument (ALBA)​

A cryptographic technique allowing a prover to succinctly demonstrate knowledge of a large dataset to a verifier. One of the proposed certificate schemes for Leios voting.

Blacklisting​

A mempool mechanism where UTXOs appearing in certified endorser blocks are temporarily marked as unavailable to prevent double-spending until they are included in a ranking block.

Boneh-Lynn-Shacham (BLS)​

A cryptographic signature scheme that allows efficient aggregation of multiple signatures into one. Used in Leios for committee voting and certificate creation.

Certificate​

A compact cryptographic proof that a quorum of votes has been reached for an endorser block. Certificates are included in ranking blocks to provide finality.

Committee​

The set of stake pool operators selected as eligible voters for a given Leios election (typically ~500 voters).

DeltaQ model​

A mathematical framework used in Leios simulations to analyse and predict real-world network behaviour (delay, loss, jitter).

Deterministic transactions​

A core Cardano property preserved in Leios: transactions either succeed completely or have no effect on the ledger (no partial execution or wasted fees).

Diffusion strategy​

The method used to propagate blocks and votes across the network. Supported strategies include:

  • Oldest-first
  • Freshest-first
  • Peer-order

Election ID​

An 8-byte identifier used to uniquely identify a voting round (typically derived from the slot number).

Endorser block (EB)​

A block that references one or more input blocks and undergoes committee voting for certification. Produced approximately every five seconds.

Fait accompli sortition​

The hybrid sortition mechanism used in Leios that combines deterministic persistent voters with randomly selected non-persistent voters for each election.

Freshest-first​

A diffusion policy that prioritises newer blocks or transactions.

Linear Leios​

The current production-oriented variant of Ouroboros Leios (CIP-0164). It retains the overall protocol structure but avoids some problems by design, allows for easier implementation and deployment while maintaining high throughput.

Mempool snapshotting​

The process of capturing the current state of pending transactions for inclusion in an input block (~72 ms in current implementations).

Mithril​

A stake-based threshold multisignature protocol that may be used for efficient voting and proof aggregation in Leios.

MUSEN​

MUlti-Stage key-Evolving verifiable random fuNctions – one of the proposed certificate schemes for Leios voting.

One EB per RB​

Current design constraint in Linear Leios: each ranking block contains at most one endorsed endorser block, keeping the chain linear and simple.

Persistent / Non-persistent voters​

Persistent voters are selected deterministically for the entire epoch; non-persistent voters are chosen per election via local sortition.

Pipeline​

A sequence of stages in Leios where input blocks, endorser blocks, and ranking blocks are produced and processed in parallel to maximise throughput.

Praos​

The current live version of Ouroboros (Ouroboros Praos) that Leios builds upon and extends.

Quorum​

The minimum number of votes required to certify an endorser block (typically 60% of the committee).

Ranking block (RB)​

The final anchoring block produced every ~20 seconds using Praos mechanics. It ranks endorsed blocks and provides the secure, linear chain.

Send-recv voting​

A two-stage voting mechanism (send phase followed by receive phase) used to improve vote propagation reliability.

Sharding (input block sharding)​

Current Leios approach that assigns input blocks to shards via VRF-derived shard-ids to reduce conflicts. Full ledger sharding is not part of Linear Leios.

Sortition​

The cryptographic process (using VRFs) for fairly selecting nodes to produce blocks or participate in voting based on stake.

Spatial efficiency​

The ratio of useful transaction data included in the ledger versus the total size of all blocks.

Temporal efficiency​

The fraction of submitted transactions that successfully make it into the final ledger.

Throughput​

The rate at which transactions are processed, measured in transactions per second (TPS). Linear Leios targets up to 1,500+ TPS.

UTXO-HD (UTXO on hard disk)​

A Cardano node optimisation that stores UTXO data on disk to reduce RAM usage, beneficial for Leios node operators.

Verifiable Random Function (VRF)​

A cryptographic primitive used in Leios for sortition, leader election, and eligibility proofs. The output is publicly verifiable but unpredictable.

Vote bundling​

Aggregating multiple votes for the same endorser block to reduce network traffic and certificate size.

Vote weight​

The stake-weighted value of each vote. Persistent voters carry full stake weight; non-persistent voters carry weight based on expected committee composition.