Crate cdk_spilman 

Spilman Payment Channels

This module implements Spilman-style unidirectional payment channels for Cashu.

A Spilman channel allows Alice (sender) to make incremental payments to Charlie (receiver) without requiring on-chain transactions for each payment. The channel uses:

• 2-of-2 multisig funding with expiry-based refund for Alice
• Deterministic output derivation using a channel secret
• Off-chain balance updates signed by Alice
• Final commitment transaction signed by both parties

Structs

BalanceUpdateMessage

A balance update message from Alice to Charlie

BridgeErrorResponse

HTTP-friendly error for payment/validation failures.

ChannelFunding

Funding data for a channel

ChannelParameters

Parameters for a Spilman payment channel

ChannelPolicy

Funding-time validation thresholds for a given unit, returned by SpilmanHost::get_channel_policy.

ChannelVerificationResult

Result of verifying a channel

ClientChannelFunding

Immutable funding data (saved once when channel is opened)

ClientChannelInfo

Information about a stored channel.

ClientPaymentState

Mutable payment state (updated on each payment)

CloseData

Data needed to close a channel

ClosePreparationError

HTTP-friendly error for close preparation.

CloseSuccess

ClosingData

Data stored when a channel enters CLOSING state

CommitmentOutputs

Commitment outputs for a specific balance distribution Contains the deterministic outputs for both sender (Alice) and receiver (Charlie) at a specific balance point in the channel

ConfigurableClientHost

A configurable client host that holds raw secret keys and uses pluggable storage.

DeterministicOutputsForOneContext

A set of deterministic outputs for a specific pubkey and amount This represents all the deterministic blinded messages, secrets, and blinding factors for splitting a given amount into ecash outputs

DeterministicSecretWithBlinding

Deterministic secret with blinding factor Can hold any type of secret (simple P2PK, P2PK with conditions, HTLC, etc.)

EstablishedChannel

An established Spilman payment channel Contains all channel components after funding transaction is complete

FundChannelResult

KeysetInfo

Keyset information for fee calculations and amount selection

MemoryClientStorage

In-memory storage implementation

OpenChannelResult

Result of opening a new channel.

OrderedListOfAmounts

An ordered list of amounts that sum to a target value

Payment

A signed payment for a Spilman channel.

PaymentProof

Payment proof for a channel

PaymentSuccess

Result of a successful payment

PaymentValidationResult

PreparedClose

Everything needed to execute a close operation after sync validation.

SpilmanBridge

Bridge for processing Spilman payments

SpilmanChannelSender

The sender’s view of a Spilman payment channel

SpilmanClientBridge

Client-side bridge for managing Spilman payment channels.

UnblindResult

Result of unblinding and verifying stage 1 swap response

UnsignedBalanceUpdate

An unsigned balance update, ready for signing.

Enums

BridgeError

ChannelState

Channel lifecycle states

ChannelVerificationError

Errors that can occur during channel verification

ClientChannelState

Channel lifecycle state

CloseError

Traits

ClientStorage

Storage trait for client channel data

MintConnection

Trait for mint connection operations needed by Spilman channels

SpilmanAsyncNetworking

Async networking hooks for the Spilman bridge

SpilmanClientAsyncNetworking

Async networking trait for client-side mint communication.

SpilmanClientHost

Trait for client-side host callbacks.

SpilmanClientNetworking

Networking trait for client-side mint communication.

SpilmanHost

Host hooks for the Spilman bridge

SpilmanNetworking

Sync networking hooks for the Spilman bridge

Functions

attach_signature_to_balance_update

Attach an externally-produced signature to an unsigned balance update.

base64_decode

Base64 decode a string (standard encoding).

build_cashu_a_token

Build a cashuA token string from proofs JSON and a mint URL.

build_cashu_b_token

Build a cashuB (v4) token string from proofs JSON, a mint URL, and a unit.

channel_parameters_get_channel_id

Get channel_id from params JSON, channel secret, and keyset info (all as strings)

compute_channel_from_token

Compute channel parameters from a Cashu token

compute_channel_secret

Compute the channel secret from a secret key and counterparty’s public key

compute_channel_secret_from_hex

Compute channel secret from hex-encoded secret key and public key

compute_funding_token_amount

Compute the minimum funding_token_amount needed for a given capacity

create_funding_outputs

Create funding outputs from params and keyset info

create_funding_swap

Create a swap request for funding a channel from existing proofs

create_signed_balance_update

Create a signed balance update for a channel

create_unsigned_balance_update

Create an unsigned balance update for a channel.

get_signatures_from_swap_request

Extract signatures from a swap request’s first proof witness

parse_keyset_info_from_json

Parse KeysetInfo from JSON

sign_with_tweaked_key_util

Utility function for SpilmanClientHost implementations to sign with a tweaked key.

unblind_and_verify_stage1_response

verify_valid_channel

Verify that a channel is valid

Type Aliases

ChannelId

Type alias for channel identifiers (hex-encoded).