Forward k1 session token in GetLiveDebitRequests for ndebit #7

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opened 2026-02-14 21:43:07 +00:00 by padreug · 0 comments

padreug commented

2026-02-14 21:43:07 +00:00

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Context

This is the Lightning.Pub side of the k1 session token feature. See lamassu-next#23 for the full proposal.

Problem

When a wallet sends a debit request (Kind 21002) after scanning an ndebit QR, Lightning.Pub forwards the request to the ATM via GetLiveDebitRequests. Currently there's no session identifier, so the ATM must match requests by amount (which has edge cases with concurrent sessions).

Proposed Change

When the CLINK spec adds an optional k1 parameter to ndebit:

ndebit:pubkey?relay=wss://...&pointer=atm&k1=abc123uniquetoken

Lightning.Pub needs to:

Accept k1 in incoming debit request events (Kind 21002)
Forward k1 in GetLiveDebitRequests responses to the ATM

Example GetLiveDebitRequests Response

Current:

{
  "requestId": "GetLiveDebitRequests",
  "npub": "npub1customer...",
  "debit": {
    "type": "invoice",
    "invoice": "lnbc...",
    "amount_sats": 5000
  }
}

With k1:

{
  "requestId": "GetLiveDebitRequests",
  "npub": "npub1customer...",
  "k1": "abc123uniquetoken",
  "debit": {
    "type": "invoice",
    "invoice": "lnbc...",
    "amount_sats": 5000
  }
}

Files to Modify

Debit request handler - parse k1 from incoming Kind 21002 events
GetLiveDebitRequests subscription - include k1 in forwarded messages

lamassu-next#23 - ATM/CLINK side implementation
LNURL-withdraw k1 pattern: https://github.com/lnurl/luds/blob/luds/03.md

## Context This is the Lightning.Pub side of the k1 session token feature. See [lamassu-next#23](https://git.atitlan.io/aiolabs/lamassu-next/issues/23) for the full proposal. ## Problem When a wallet sends a debit request (Kind 21002) after scanning an ndebit QR, Lightning.Pub forwards the request to the ATM via `GetLiveDebitRequests`. Currently there's no session identifier, so the ATM must match requests by amount (which has edge cases with concurrent sessions). ## Proposed Change When the CLINK spec adds an optional `k1` parameter to ndebit: ``` ndebit:pubkey?relay=wss://...&pointer=atm&k1=abc123uniquetoken ``` Lightning.Pub needs to: 1. **Accept `k1`** in incoming debit request events (Kind 21002) 2. **Forward `k1`** in `GetLiveDebitRequests` responses to the ATM ### Example GetLiveDebitRequests Response **Current:** ```json { "requestId": "GetLiveDebitRequests", "npub": "npub1customer...", "debit": { "type": "invoice", "invoice": "lnbc...", "amount_sats": 5000 } } ``` **With k1:** ```json { "requestId": "GetLiveDebitRequests", "npub": "npub1customer...", "k1": "abc123uniquetoken", "debit": { "type": "invoice", "invoice": "lnbc...", "amount_sats": 5000 } } ``` ## Files to Modify - Debit request handler - parse `k1` from incoming Kind 21002 events - GetLiveDebitRequests subscription - include `k1` in forwarded messages ## Related - [lamassu-next#23](https://git.atitlan.io/aiolabs/lamassu-next/issues/23) - ATM/CLINK side implementation - LNURL-withdraw k1 pattern: https://github.com/lnurl/luds/blob/luds/03.md