Encyclopedia Bitcoin basics · Entry 188
Offline Bitcoin signing: build, inspect, sign and broadcast
In this article
At a glance
Key facts
Build a proposal using public wallet information
A watch-only wallet can identify candidate outputs and create a transaction to a recipient. It does not need private keys for that preparation. A PSBT can include previous-output and derivation information that an offline signer needs to interpret the spend.
Keep the intended recipient information available through a trusted channel. The signer should not accept a host-provided destination because the rest of the file parses successfully.
Use a value check alongside destination review
Suppose the inputs total 120,000 satoshis, the recipient gets 70,000 and recognized change is 48,500. The remaining 1,500 is the fee. The signer must also establish that the apparent change belongs to the intended wallet; arithmetic alone cannot authenticate that output.
BIP-174 defines signer checks for previous-output data and signing conditions. An offline device without trustworthy transaction context can still authorize an unintended payment.
Treat transfer and broadcast as separate steps
After signing, return the supported transaction file to the online side, finalize or extract it where required, then broadcast. USB, camera or removable-card transfer changes how data moves; it does not remove the need for authentic software and careful parsing.
A signed file is not evidence of confirmation. Track the transaction after relay, preserving the recipient output and observed chain context.
Direct answers
Questions people ask
Does an unsigned PSBT let someone steal the funds?
An unsigned proposal is not itself a signature. It can still reveal wallet information or mislead an incautious signer, and some PSBTs already contain signatures or sensitive derivation data. Inspect what the particular file includes.
Does offline signing mean I never need an internet connection?
The signing device can remain offline, but a network participant must eventually relay the signed transaction and observe the chain. A separate online device commonly performs those jobs.
Inspect the evidence
The answer and key facts have stable claim links. These records retain the scope and qualification when reused.
Offline signing separates transaction preparation and broadcast from private-key authorization. An online wallet prepares an unsigned proposal, an offline signer checks and signs it, and an online node relays the signed result. PSBT is one standardized way to carry the required information. Offline status protects only part of the process: the proposed destination, fee and spending policy still need validation.
Educational explanation. Product-specific behavior is scoped to the cited documentation, checked 2026-10-02.
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimUnsigned file: Can carry a proposal without spending authority
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimSigning: Requires the relevant keys and policy checks
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimBroadcast: Needs a network-connected relay after signing
Scope: Bitcoin · data through 2026-10-02. Verification: verified · 2026-10-02T19:29:20.637Z.
Link to this claimRevision history
- — First publication after primary-source research and separate automated verification.
Source register
Sources and references
Retrieval dates and locators are recorded individually.- Cold StorageElectrum
Electrum offline signing workflow and separation of watch-only and signing devices.
Locator: Create an offline wallet; Create a watching-only version of your wallet; Create an unsigned transaction; Get your transaction signed; Broadcast your transaction · Retrieved: 2026-10-02T18:53:56.455ZOpen source - Partially Signed Bitcoin Transaction FormatBitcoin Improvement Proposals
Offline signing workflow, UTXO information and separate signing/finalization/broadcast steps.
Locator: Roles; Creator; Signer; Transaction Extractor · Version / scope: Pinned BIPs revision · Retrieved: 2026-10-02T18:53:54.151ZOpen source - TransactionsBitcoin developer documentation
Inputs, outputs, authorization, change, coinbase exceptions and fee accounting.
Locator: Introduction; Spending An Output; P2PKH Script Validation; Multisig; Transaction Fees And Change; Avoiding Key Reuse · Version / scope: Developer guide; historical implementation details require qualification · Retrieved: 2026-10-02T18:53:53.759ZOpen source
Research and drafting use AI assistance. A separate automated review checks claims against primary sources; no external expert or named human review is implied. Publication, substantive editing, source retrieval and verification are recorded separately. This version was independently checked by an automated reviewer on 2 October 2026.
Editorial method and correctionsDegrees of Satoshi editorial project. “Offline Bitcoin signing: build, inspect, sign and broadcast.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/bitcoin-offline-signing/