TYPE 0x0503 · ANCHOR FAMILY

ANCHOR_POOL

VTXO pool anchor. Verifies a pool Merkle root and participant count. Used to commit the state of Ark-style virtual transaction output pools on-chain.

Anchor Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
vtxo_tree_root	HASH256	32 B	Conditions	Merkle root of the VTXO pool tree
participant_count	NUMERIC	1-4 B	Conditions	Number of participants in the pool (must be > 0)

No witness fields required. Both the tree root and participant count are committed in conditions.

Wire Format Breakdown

0x0503 0 2 HASH256 · 32B NUMERIC · 3B Conditions = 43 bytes

0x0503 0 0 Witness = 4 bytes (empty block)

Total 47 bytes

Evaluation Logic

1.Extract HASH256 field for vtxo_tree_root

2.If no HASH256 field present → ERROR

3.Read participant_count from NUMERIC field

4.If participant_count ≤ 0 → UNSATISFIED

5.Otherwise → SATISFIED

Return Values

Condition	Result
Missing HASH256 field (no tree root)	ERROR
Missing NUMERIC field	ERROR
participant_count ≤ 0	UNSATISFIED
Hash present + participant_count > 0	SATISFIED

JSON Wire Format

Conditions (VTXO pool with 128 participants)

{
  "type": "ANCHOR_POOL",
  "inverted": false,
  "fields": [
    { "type": "HASH256", "hex": "b3f1a7e9...vtxo tree root...32 bytes" },
    { "type": "NUMERIC", "value": 128 }
  ]
}

Anchors a VTXO pool tree root with 128 participants. The root commits to all virtual transaction outputs in the pool.

Use Cases

Ark-style VTXO Pools

Commit the Merkle root of a virtual transaction output pool on-chain. Participants can prove their VTXO exists in the pool by providing a Merkle proof against the anchored root, enabling off-chain UTXO management with on-chain settlement guarantees.

Joinpool State Commitment

Anchor the current state of a joinpool — a shared UTXO managed by multiple participants. The tree root captures everyone's balance, while the participant count enables on-chain verification of pool size constraints.

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