DA-03 · LESSON 05

Single-transaction actions

KEY DEFINITIONS

Terms used in this lesson

Vault: A set of Bitcoin outputs and spending rules that holds collateral and represents the current loan state.
Hash160: SHA-256 followed by RIPEMD-160, producing the 20-byte hash used by several Bitcoin spending conditions.
Preimage: The original secret data whose hash equals a previously committed value.
UNIT: Ducat’s dollar-pegged stablecoin, the asset a borrower can create against bitcoin collateral.
Collateral: An asset pledged against a debt; it can be used to cover the debt if agreed conditions are breached.
Proof-of-work target: The maximum header-hash value accepted for a block; lowering it makes valid hashes harder to find.
BTC: The common market ticker for bitcoin.
Witness: Signatures, scripts, or other data supplied to satisfy a Bitcoin output’s spending condition.

Deposit, withdraw, repo, and trim update vault state without the separate issuance or burn pattern.

35 min Difficulty 4/5 Not started

VISUAL MODEL

See the whole mechanism before going step by step

Use the diagrams to orient yourself. Then the guided explanation below teaches every part in depth.

4 explanatory views

CONCEPT-SPECIFIC MAP · ducat vaultA Ducat action moves one Bitcoin-anchored vault state to a successorSelect any state to inspect its exact role.

RELATIONSHIP MAPInputs, rule, and outputs

01
PREDECESSORCurrent vault outpoint
The current Bitcoin output anchors collateral and identifies the state being spent.
02
REQUESTSingle-transaction actions
The Single-transaction actions workflow proposes one exact action and successor state.
03
POLICYProfile, oracle, signatures
Applicable policy, price evidence, authorization, and transaction shape are checked.
04
BITCOIN SPENDScript-valid transaction
Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules.
05
SUCCESSORNew outpoint and state
Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

Rule shown: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state.

STAGE 1 OF 5PREDECESSOR: Current vault outpoint

The current Bitcoin output anchors collateral and identifies the state being spent.

Governing relationship: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state. Complete path: 1. PREDECESSOR, Current vault outpoint. The current Bitcoin output anchors collateral and identifies the state being spent. 2. REQUEST, Single-transaction actions. The Single-transaction actions workflow proposes one exact action and successor state. 3. POLICY, Profile, oracle, signatures. Applicable policy, price evidence, authorization, and transaction shape are checked. 4. BITCOIN SPEND, Script-valid transaction. Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules. 5. SUCCESSOR, New outpoint and state. Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

1. State transitionWhat exists, what changes, and what results

BEFORE

Use a 0.75 BTC, 30,000 UNIT owner vault, a 0.4 BTC, 8,000 UNIT liquidator vault, and a 0.25 BTC, 16,000 UNIT target. Required practice uses another ledger.

MECHANISM

Deposit and withdraw modify one owner's collateral; repo and trim consume liquidator and unsafe-vault state under liquidation rules.

AFTER

Relabelling deposit bytes cannot supply repo or trim roles, witness, or conservation and is rejected. Required practice uses a separate server-executed vector.

Text equivalent: Starting from Use a 0.75 BTC, 30,000 UNIT owner vault, a 0.4 BTC, 8,000 UNIT liquidator vault, and a 0.25 BTC, 16,000 UNIT target. Required practice uses another ledger. The mechanism begins when Deposit and withdraw modify one owner's collateral; repo and trim consume liquidator and unsafe-vault state under liquidation rules. The resulting lesson is Relabelling deposit bytes cannot supply repo or trim roles, witness, or conservation and is rejected. Required practice uses a separate server-executed vector.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 4

Choose the action layout

Deposit and withdraw modify one owner's collateral; repo and trim consume liquidator and unsafe-vault state under liquidation rules.

Complete path: 1. Choose the action layout: Deposit and withdraw modify one owner's collateral; repo and trim consume liquidator and unsafe-vault state under liquidation rules. 2. Gather every prior output: The transaction includes current vaults, wallet funding, and any protocol inputs required by that action. 3. Create action-specific successors: Outputs encode the permitted resulting vault, collateral, debt, claimant, and reserve relationships. 4. Validate atomically: All required relationships succeed or the single Bitcoin transaction is rejected; there is no separate token parent to reconcile.

3. Rule and failure boundaryWhat accepts the result and where it can stop

ACCEPTED PATH

The worked case executes the named inputs and checks in the displayed order. All required relationships succeed or the single Bitcoin transaction is rejected; there is no separate token parent to reconcile.

CHANGED CONDITION

A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Single describes package shape only. Each action still has a distinct parser, role map, validation, and witness requirement.

Important distinction: Single-transaction actions all share the same inputs and signatures. Single describes package shape only. Each action still has a distinct parser, role map, validation, and witness requirement.

Text equivalent: The accepted path is enforced by The worked case executes the named inputs and checks in the displayed order. All required relationships succeed or the single Bitcoin transaction is rejected; there is no separate token parent to reconcile. If the required condition changes, A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Single describes package shape only. Each action still has a distinct parser, role map, validation, and witness requirement.

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Learn the idea

A single-transaction action changes vault state without a separate UNIT issue or burn parent. Deposit adds owner collateral. Withdraw removes permitted owner collateral. Repo is a full liquidation path that closes an unsafe vault under its liquidation rules. Trim is a partial liquidation path that reduces exposure while leaving a successor vault. A cleared target marker is the action-specific minimal output used by the captured parser to record that a liquidated target no longer carries its former live vault state. Single describes package shape, not shared economic meaning.

GUIDED EXPLANATION1/4 ideas inspected

Choose the action layout

Deposit and withdraw modify one owner's collateral; repo and trim consume liquidator and unsafe-vault state under liquidation rules.

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“Single-transaction actions all share the same inputs and signatures.”

Single describes package shape only. Each action still has a distinct parser, role map, validation, and witness requirement.

FINISH LEARNING FIRST

The questions unlock after every required learning activity

Inspect every guided idea, open the worked example, rebuild its mechanism, and complete the deterministic lesson tool. Your progress is saved automatically.