Glossary

A

Archival Node Node responsible for long-term storage and retrieval of historical message payloads beyond the retention window.

Availability Certificate (AC) Cryptographic proof that a supermajority of a lane committee attested to data availability.

Availability Finality Point at which message data is confirmed retrievable via a valid Availability Certificate.

B

Bid Amount of OBS paid for Priority Message inclusion (signed-debit economics).

C

Canonical Block Single block produced per slot that determines ordering, execution, and finality for transactions and message commitments.

Canonical Ordering Permanent ordering of messages determined by inclusion of lane batch headers in finalized blocks.

Chain ID Network identifier. Obsidian uses 421 (0x1a5).

Committee Quorum Threshold of committee signatures (2/3) required to form a valid Availability Certificate.

D

Data Commitment Merkle root of erasure-coded chunks that commits to sidecar content.

Data Plane The sidecar layer that delivers actual message payload bytes via erasure-coded chunks.

E

Epoch Consensus time period of SLOTS_PER_EPOCH slots.

Erasure Coding Redundancy technique (Reed-Solomon) allowing data reconstruction from partial chunks.

I

Inclusion Finality Point at which message ordering becomes permanent due to block finalization.

L

Lane Parallel processing channel to which messages are deterministically routed by sender address.

Lane Batch Header Compact header containing message ordering, data commitments, and economic metadata; included in the canonical block.

Lane Committee Subset of validators responsible for verifying data availability for a specific lane.

Lane Leader Validator elected per slot to batch, encode, and distribute messages for a lane.

Lane Router Deterministic routing logic that assigns messages to lanes based on sender address.

lane_headers_root Keccak256 merkle root of all LaneBatchHeaders in a block. Present in header.

M

Message A signed data payload submitted to Obsidian. Contains sender, payload, nonce, chainId, signature.

Message Commitment Cryptographic reference included in the canonical block that binds a message batch to its payload bytes without embedding the data itself.

Message ID Deterministic hash identifying a message, derived from sender, payload commitment, nonce, and signature.

Micro Root Merkle root of message identifiers that commits to message ordering within a batch.

N

Nonce Unique value per message preventing replay attacks.

O

OBS Native token of Obsidian Chain.

P

Payload The data content of a message. Maximum size is 8 KB. Protocol treats as opaque bytes.

PoP (Proof of Possession) Proof provided by committee members demonstrating possession of assigned erasure-coded chunks prior to voting.

Priority Message (PM) Message with bid greater than MinPMBid; fee-based and ordered by bid amount within a lane batch.

R

Reed-Solomon Encoding Error-correcting code that splits data into redundant chunks such that any subset above a threshold can reconstruct the original payload.

Retention Window Period during which validators are required to store and serve message data after inclusion.

S

Serve Obligation Requirement for committee members to serve sidecar chunks on request.

Sidecar Data object containing message payloads; propagated separately from the canonical block body.

Sidecar Chunks Individual erasure-coded fragments of a sidecar distributed across lane committee members.

Silica Protocol Obsidian's data availability subsystem responsible for message routing, encoding, distribution, and availability verification.

Standard Message (SM) Message with zero bid that requires a VDF proof and follows FIFO ordering within its lane.

T

TargetBlock Block number a message targets for inclusion; message expires if the validity window passes.

V

VDF (Verifiable Delay Function) Proof of sequential computation that cannot be parallelized and can be efficiently verified.