SPIN-Related

Terms (A–Z)

A

Anchor Chain

Consensus

High-value PoS network (like Polkadot) that validates and finalizes Fast Chain proofs to provide additional security guarantees.

Comment: Provides second-tier finality for Fast Chain blocks. Previously called "slow chain" (same as in Thunderella paper) and "Relay Chain" in early drafts

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B

Block Batch

Consensus

Set of Fast Chain finalized blocks submitted to Anchor Chain in one transaction through the Bridging Gadget.

Comment: Reduces overhead by batching multiple blocks for Anchor Chain validation.

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Bridging Gadget

Consensus

Finite State Machine executed on Anchor Chain that validates Fast Chain Finality Proofs and manages recovery procedures.

Comment: Core component enabling SPIN's hybrid consensus. Implemented as custom parachain runtime on Polkadot Relaychain.

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Bridging Gadget Operators

Consensus

Validators responsible for operating the Bridging Gadget, submitting FCFPs to the Anchor Chain, and managing cross-chain communication.

Comment: In SPIN, the Operators Set equals the Validators Set for simplicity. Rotation not tied to Primary Leader Tenure. Previously called "Collation Leader" in older drafts.

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E

Election Finalization Block

Consensus

Specific block where validator election results are determined and finalized, occurring after the Last Voting Block.

Comment: Either accepts off-chain Phragmen solutions or triggers on-chain calculation by Primary Leader.

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Epoch

Consensus

A block production period with pre-known starting time and fixed-length during which the set of block producers stays constant. Epochs are indexed sequentially and divided into equal-length periods known as block production slots. Each slot is awarded to a subset of block producers during which they are allowed to generate a block. Governance, nomination, and validator selection processes occur within epoch boundaries to determine the validator set for subsequent epochs.

Comment: Detailed mechanics in older drafts.

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F

Fast Chain

Consensus

QF Network's main blockchain with 100ms target block time that processes normal transactions and maintains sovereignty while anchoring to Polkadot.

Comment: The primary chain users interact with, enhanced with additional security from Anchor Chain.

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Fast Chain Finality Proof (FCFP)

Consensus

Cryptographic proof consisting of block hash signed by majority of Fast Chain Validators, submitted to Anchor Chain for validation.

Comment: Core mechanism for transferring finality from Fast Chain to Anchor Chain.

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Fast Chain Nominations Proof (FCNP)

Consensus

Cryptographic proof containing sufficient data for verifying Fast Chain nominations changes.

Comment: Used during validator set elections to prove nomination validity.

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Fast Chain Validator Set Proof (FCVSP)

Consensus

Cryptographic proof containing sufficient data for verifying Fast Chain validator set changes.

Comment: Enables Anchor Chain to verify validator set elections and rotations.

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FCFP Block

Consensus

A block whose hash and finality justifications are included in a Fast Chain Finality Proof.

Comment: The specific block being proven to the Anchor Chain.

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FCFP Tail

Consensus

Sequence of blocks covered by a single FCFP, from the FCFP Block back to the previous FCFP Block.

Comment: Defines the scope of blocks validated in each proof submission.

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FCFP Transaction

Consensus

Transaction submitted to Bridging Gadget containing FCFP along with block batch headers.

Comment: Primary mechanism for transferring finality information from Fast Chain to parachain.

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Finality Recovery Mode

Consensus

Emergency procedure activated when Fast Chain finality stalls, using Anchor Chain to restore consensus and elect new Primary Leader.

Comment: Ensures liveness even when Fast Chain consensus fails. Detailed procedures in older drafts. Secondary Leaders produce operational-only blocks during recovery.

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I

Inclusion Proof

Consensus

Cryptographic proof showing that a specific transaction was included in a finalized Fast Chain block.

Comment: Generated by Primary Leader in response to Yell Queries to prove transaction inclusion.

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L

Last Voting Block

Consensus

Designated block after which no more validator candidate intentions or nominator votes can be submitted during an epoch.

Comment: Marks deadline for election participation before vote tallying begins.

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M

Mode Switch Proof

Consensus

Fast Chain transaction proving recent mode change (recovery/operational) in the parachain, containing mode value and parachain finality proof.

Comment: Enables Fast Chain to track and respond to parachain state changes.

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N

Normal Transactions

Consensus

All blockchain transactions excluding operational transactions - regular user and smart contract transactions.

Comment: Only processed by Primary Leader during normal operation, excluded during Secondary Leader block production.

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O

Operational Transactions

Consensus

Blockchain transactions required for maintaining network operation, such as consensus messages and validator updates.

Comment: Can be processed by Secondary Leaders during recovery to maintain chain liveness.

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P

Primary Leader

Consensus

Designated Fast Chain validator responsible for producing blocks with normal transactions during assigned tenure.

Comment: Selected deterministically from validator set. Can be challenged through Yell Query mechanisms.

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S

Secondary Leader

Consensus

Backup block producer that activates when Primary Leader fails, maintaining chain liveness during recovery procedures.

Comment: Maintains network operation during Primary Leader failure. Detailed ranking system in older drafts.

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T

Tenure

Consensus

Fixed time period during which a single Primary Leader produces blocks before rotation to next validator.

Comment: Longer than individual block times to reduce network overhead while maintaining decentralization.

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W

Witness Message

Consensus

Message submitted by validators during Finality Recovery Mode containing the latest finalized block hash produced by Primary Leader.

Comment: Used for accountability - validators failing to submit are disabled by next Primary Leader.

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Y

Yell Query

Consensus

Anti-censorship mechanism allowing users to submit transactions to Bridging Gadget when they suspect Fast Chain censorship.

Comment: Forces Primary Leader to provide Inclusion Proof or triggers Finality Recovery Mode. More details in older drafts.

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Yell Target Transaction (YTT)

Consensus

Specific transaction that user believes is being censored by Primary Leader, referenced in Yell Query.

Comment: Must be included by Primary Leader with Inclusion Proof or triggers recovery procedures.

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