DA-04 · LESSON 01

Guardian responsibilities

KEY DEFINITIONS

Terms used in this lesson

Guardian: A Ducat policy-checking signer that can authorize or reject defined protocol transactions.
Vault: A set of Bitcoin outputs and spending rules that holds collateral and represents the current loan state.
Validator: Software or a participant that independently checks state transitions under a system's rules. The exact role depends on the protocol being discussed.
Oracle: A system that reports outside information, such as a market price, for use by a protocol.
Outpoint: A transaction ID plus output number that identifies one exact prior output.
Collateral: An asset pledged against a debt; it can be used to cover the debt if agreed conditions are breached.
Sighash: The exact transaction digest and signature mode that determine which fields a Bitcoin signature authorizes.
UNIT: Ducat’s dollar-pegged stablecoin, the asset a borrower can create against bitcoin collateral.
BTC: The common market ticker for bitcoin.

Guardians receive signed requests, validate protocol rules and transaction structure, reserve issuance accounts, and contribute authorization when policy permits.

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
REQUESTGuardian responsibilities
The Guardian responsibilities 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, Guardian responsibilities. The Guardian responsibilities 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

Vault outpoint loan-alt:1 represents 80,000,000 sats collateral and 30,000 UNIT debt. At an illustrative 90,000 dollar price and 160 percent minimum ratio, the owner requests…

MECHANISM

The request identifier, action, current vault outpoint, proposed transaction bytes, covered input, network, profile, and oracle context must describe one operation. Replaying…

AFTER

The Guardian independently verifies both economic state and exact authorization. A valid owner signature and collateral ratio are necessary checks, not substitutes for the re…

Text equivalent: Starting from Vault outpoint loan-alt:1 represents 80,000,000 sats collateral and 30,000 UNIT debt. At an illustrative 90,000 dollar price and 160 percent minimum ratio, the owner requests 20,000,000 sats with a 40,000 sat total fee.… The mechanism begins when The request identifier, action, current vault outpoint, proposed transaction bytes, covered input, network, profile, and oracle context must describe one operation. Replaying the identifier with different bytes is a sub… The resulting lesson is The Guardian independently verifies both economic state and exact authorization. A valid owner signature and collateral ratio are necessary checks, not substitutes for the rest of the manifest.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 4

Receive one bound request

The request identifier, action, current vault outpoint, proposed transaction bytes, covered input, network, profile, and oracle context must describe one operation. Replaying the identifier with different bytes is a substitution attempt.

Complete path: 1. Receive one bound request: The request identifier, action, current vault outpoint, proposed transaction bytes, covered input, network, profile, and oracle context must describe one operation. Replaying the identifier with different bytes is a substitution attempt. 2. Reconstruct before signing: The Guardian loads the current state and independently checks action-specific inputs, outputs, collateral or debt change, oracle context, fee bounds, owner authorization, and successor commitments. 3. Coordinate protected resources: For issuance-related flows, Guardians coordinate reservations so the same issuance capacity is not granted twice. 4. Contribute authorization or reject: A valid request proceeds to its signing flow. The Guardian signs the signature hash, or sighash, which is the exact message Bitcoin derives for the covered transaction input. An invalid or ambiguous request is rejected rather than corrected silently.

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

ACCEPTED PATH

The Guardian must reconstruct exact satoshi conservation, unchanged debt, ratio policy, owner signature message, request identity, profile, oracle snapshot, covered input, and capacity reservation before releasing its authorization.

CHANGED CONDITION

A stale outpoint, altered recipient, nonconserving successor, changed debt, stale profile or oracle, invalid owner signature, wrong signing input, or over-reservation rejects before Guardian nonce or signature use.

Important distinction: A Guardian is the same thing as a validator. Validators reconstruct and check protocol state; Guardians control signing authority. Combining or confusing those roles changes the security model.

Text equivalent: The accepted path is enforced by The Guardian must reconstruct exact satoshi conservation, unchanged debt, ratio policy, owner signature message, request identity, profile, oracle snapshot, covered input, and capacity reservation before releasing its authorization. If the required condition changes, A stale outpoint, altered recipient, nonconserving successor, changed debt, stale profile or oracle, invalid owner signature, wrong signing input, or over-reservation rejects before Guardian nonce or signature use.

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Learn the idea

A Ducat Guardian is a policy-enforcing signer. A withdrawal manifest binds the action, current outpoint, proposed successor collateral and debt, owner recipient, covered input, profile, oracle context, request identifier, and owner signature. The Guardian reconstructs value conservation from the transaction rather than accepting a summary or transaction hash blindly.

GUIDED EXPLANATION1/4 ideas inspected

Receive one bound request

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“A Guardian is the same thing as a validator.”

Validators reconstruct and check protocol state; Guardians control signing authority. Combining or confusing those roles changes the security model.

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