Review of Spark's trust model

Unilateral-exit readiness

The documented self-operated exit requires external on-chain fee funding before Spark value is available

The documented independent exit requires external on-chain fee funding before the Spark value becomes spendable on chain. A third party could sponsor the UTXO, but doing so replaces the user's funding requirement with a service dependency. 123

4 sourcesEvidence reviewed through July 14, 2026

What the evidence shows

Technical and product details

  1. Documented mechanism

    In the current procedure, pre-signed Spark exit and refund transactions pay zero fee and are relayed with fee-paying CPFP children. 12

    Supporting material shown on this page

  2. Manual requirement

    Spark tells mainnet users to bring sufficient L1 UTXOs and use Bitcoin Core v29 submitpackage. 1

    Supporting material shown on this page

  3. Timing consequence

    The Spark value is not yet available as an ordinary spendable L1 output when those fee children must be funded. 12

    Supporting material shown on this page

  4. Independent-user consequence

    A user relying only on the documented independent path cannot begin with a Spark balance alone; an external fee source must first supply a suitable UTXO. 13

    Supporting material shown on this page

Scope control

What this does not establish

  • The external UTXO need not always be personally supplied by the user. A wallet or sponsor could provide fee funding, but that replaces the user-funding requirement with dependency on that sponsor. It does not remove the documented standard-relay path's requirement for a fee-paying input outside the Spark balance. 4

Sources and excerpts

Primary sources

The relevant details and available source-code excerpts appear alongside the claims above. This list preserves the complete original-source trail for independent verification.

1

Spark unilateral-exit manual

Official documentation · docs.spark.money · Live source · checked 2026-07-14

Open original source
2

Spark package constructor

Pinned source code · github.com · Pinned or archival · checked 2026-07-14

Open original source
3

Blink funding transaction

On-chain transaction · mempool.space · Pinned or archival · checked 2026-07-14

Open original source
4

Blink mobile integration plan

Pinned source code · github.com · Pinned or archival · checked 2026-07-14

Open original source

How sources, absence findings, and limitations were evaluated