Table of Contents

Class OnchainHtlc

Namespace
NArk.ArkadeIntents.Onchain
Assembly
NArk.ArkadeIntents.dll

The Bitcoin-L1 half of an onchain corridor swap: a two-leaf taproot HTLC.

public sealed record OnchainHtlc : IEquatable<OnchainHtlc>
Inheritance
OnchainHtlc
Implements
Inherited Members

Remarks

The internal key is the BIP-341 NUMS point, so there is no key-path spend, ever — the only ways out are the two leaves, and both are visible to whoever holds the address.

Both sides of a swap derive this independently and must land on the same address, so every byte here is part of the wire contract. NArk.Tests/ArkadeIntents/Fixtures/onchain_htlc.json pins it against the counterparty's own derivation; a drift is an address one side cannot spend.

Constructors

OnchainHtlc(BitcoinAddress, Script, Script, Script, ControlBlock, ControlBlock, uint256, LockTime)

The Bitcoin-L1 half of an onchain corridor swap: a two-leaf taproot HTLC.

public OnchainHtlc(BitcoinAddress Address, Script PkScript, Script ClaimLeaf, Script RefundLeaf, ControlBlock ClaimControlBlock, ControlBlock RefundControlBlock, uint256 PaymentHash, LockTime RefundLocktime)

Parameters

Address BitcoinAddress
PkScript Script
ClaimLeaf Script
RefundLeaf Script
ClaimControlBlock ControlBlock
RefundControlBlock ControlBlock
PaymentHash uint256
RefundLocktime LockTime

Remarks

The internal key is the BIP-341 NUMS point, so there is no key-path spend, ever — the only ways out are the two leaves, and both are visible to whoever holds the address.

Both sides of a swap derive this independently and must land on the same address, so every byte here is part of the wire contract. NArk.Tests/ArkadeIntents/Fixtures/onchain_htlc.json pins it against the counterparty's own derivation; a drift is an address one side cannot spend.

Fields

LockTimeThreshold

Below this, a locktime means a block height rather than a timestamp (BIP-65).

public const long LockTimeThreshold = 500000000

Field Value

long

PreimageSize

The preimage length the claim leaf accepts, in bytes.

public const int PreimageSize = 32

Field Value

int

Properties

Address 

public BitcoinAddress Address { get; init; }

Property Value

BitcoinAddress

ClaimControlBlock 

public ControlBlock ClaimControlBlock { get; init; }

Property Value

ControlBlock

ClaimLeaf 

public Script ClaimLeaf { get; init; }

Property Value

Script

PaymentHash 

public uint256 PaymentHash { get; init; }

Property Value

uint256

PkScript 

public Script PkScript { get; init; }

Property Value

Script

RefundControlBlock 

public ControlBlock RefundControlBlock { get; init; }

Property Value

ControlBlock

RefundLeaf 

public Script RefundLeaf { get; init; }

Property Value

Script

RefundLocktime 

public LockTime RefundLocktime { get; init; }

Property Value

LockTime

Methods

Derive(uint256, ECXOnlyPubKey, ECXOnlyPubKey, long, Network)

Derive the HTLC both sides of the swap must agree on.

public static OnchainHtlc Derive(uint256 paymentHash, ECXOnlyPubKey claimKey, ECXOnlyPubKey refundKey, long refundLocktime, Network network)

Parameters

paymentHash uint256

SHA-256 of the preimage; the leaf commits to its HASH160.

claimKey ECXOnlyPubKey

The x-only key that spends by revealing the preimage.

refundKey ECXOnlyPubKey

The x-only key that spends after refundLocktime.

refundLocktime long

Absolute unix seconds; consensus matures it against median time past.

network Network

The L1 network the address is rendered for.

Returns

OnchainHtlc

The derived HTLC.

Remarks

The claim leaf is OP_SIZE 32 OP_EQUALVERIFY OP_HASH160 <h160> OP_EQUALVERIFY <claimKey> OP_CHECKSIG, the refund leaf <locktime> OP_CLTV OP_DROP <refundKey> OP_CHECKSIG.

The length check on the claim leaf is not decoration: without it the leaf accepts any witness value whose HASH160 matches, and this contract's preimage is exactly 32 bytes by construction — the same prefix real HTLC scripts carry, for the same reason.

Exceptions

ArgumentOutOfRangeException

refundLocktime is not a positive timestamp, or is height-shaped.

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