bfinger

Warning

Experimental software. bfinger is part of bstack, the applications and patterns built on BSV Layered Multicast. It is published to be built on and improved. Interfaces, formats and behavior may change rapidly between releases; pin an exact version.

A Bitcoin-era descendant of the UNIX finger command. Ask what user@domain currently says about itself and get an answer that proves itself, instead of one you trust because of who handed it over.

$ bfinger 1bsv@lightweb.net -yes | head -4
1bsv@lightweb.net
  VERIFIED   signature, sequence 2 (update), proof at height 968974
  key        03dd1a…3902  (pinned 2026-10-07 (first contact))
  org        Lightweb Inc.
$ bfinger 1bsv@lightweb.net -field status
1971 called; the .plan is back.

That is a live mainnet address; run it as written.

Publishing your own needs no node and no server of your own: install, bfinger init, pay the fund address it prints from your wallet (or hand over the payment's BEEF), bfinger fund, publish. Public services carry the rest (WhatsOnChain, a public broadcaster), and every one is a setting you can point at your own node instead.

New here? Start with QUICKSTART.md.

How it works

flowchart LR
  R["bfinger (you)"] -->|"1. who is alice?"| D["example.com<br/>manifest + resolve"]
  R -->|"2. lookup"| H["overlay hosts<br/>any replica"]
  R -->|"3. headers"| S["header source<br/>proof of work checked"]
  H -. record + Bitcoin proof .-> R
  O["owner"] -->|publish| H
  O -->|one small tx per update| B[("BSV blockchain")]
  B -.-> S
  %% The last node is an invisible spacer in the rightmost rank: the rendered
  %% viewer places its zoom and pan controls over the bottom-right corner.
  B ~~~ pad
  pad["&nbsp;<br/>&nbsp;<br/>&nbsp;<br/>&nbsp;<br/>&nbsp;"]:::pad
  classDef pad fill:none,stroke:none,color:transparent

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• The domain names the key. example.com answers which identity key is alice; your copy of bfinger pins that key on first contact and refuses a changed key unless the old one signed the rotation.
• The domain names its hosts, too. The same /manifest.json lists the overlay services that answer for the domain under metanet.overlays, as BRC-180 specifies, so bfinger asks the lookup host the domain declares (ls_finger) and never guesses a hostname. bfinger domain-docs writes that entry, and tm_finger for submissions, for you. A declared host is still only a claim: everything it serves is checked.
• Hosts are replicas, not authorities. Any host can serve the record. One that edits it produces something that fails the check, so bfinger refuses it. Ask several with -quorum 2.
• The chain holds the state, not the data. Each update mines a few hundred bytes that commit to the record and spend the previous update, so the history cannot fork. The record itself travels beside it in a transaction that is never mined, which is why the owner can retract it.
• You check everything. Signature, proof, sequence and key, against block headers whose proof of work bfinger checks itself. VERIFIED means all of it passed. Exit status is 0 verified, 1 refused, 2 usage or transport failure; never 0 on an unverified answer.

The argument in full: docs/overview.md. bfinger is the worked example in the pattern paper The bstack: publish once, prove everything, and let users ride free.

Install

Container	docker run --rm -it ghcr.io/lightwebinc/bfinger alice@example.com (linux/amd64, linux/arm64)
Binary	Releases: static builds for Linux and macOS, amd64 and arm64, with SHA256SUMS
Go	go install github.com/lightwebinc/bfinger/cmd/bfinger@latest (Go 1.27.2 or later)
A host of your own	HOST=finger.example.com docker compose up -d with the release's compose.yaml (docs/self-host.md), or one CloudFormation stack on AWS (deploy/aws)

Documentation

If you want to	Read
Try it in five minutes, on mainnet	QUICKSTART.md
Read, verify and pin addresses; publish and update your own record	docs/user-guide.md
Look up a setting, flag or environment variable	docs/configuration.md
Copy a working command (mainnet, testnet, a local regtest sandbox)	docs/examples.md
Run a host and make your domain answer for handles	docs/self-host.md
Load the modules into an overlay host you already run	host/README.md
Understand why it is built this way	docs/overview.md
See the components and how data and payments flow	docs/architecture.md
See every operation as a diagram	docs/flows.md
Know who learns what from a lookup or a publication	docs/privacy.md
Implement a compatible reader or host	docs/committed-record.md (the specification), docs/known-keys.md, docs/host-selection.md
Find your way around the code	docs/internals.md, docs/owner-flow.md

Status

Built and working end to end: the reader (lookups, verify, -watch, -json, key pinning), the publisher (init, fund, create, status, rotate, retire, kill, pay, receive, publish -resume, doctor, domain-docs, serve-wallet), sub-stores, and the two overlay host modules with a container image and a one-file host stack.

Designed, not built yet: handle-certificate verification (BRC-52, built in borg, a sibling application; not yet adopted here), a messagebox for payment notices (bbox, a sibling application; bfinger pay writes its notice to a local file until it delivers over one), delegation and the named stores it writes, host-side charging for lookups, content only a payer can read (BRC-369), and a reader-side spend check. docs/architecture.md lists them all, and docs/overview.md explains the hook that makes each possible.

Build

make verify         # what CI runs: format, vet, dependency set, licenses, build, tests under -race
make host-docker    # the host modules and their tests, in Node 24
make docker-build   # the command's image
make dist           # the release tarballs

Two direct Go dependencies, both pinned exactly and asserted by make verify: go-sdk and bcommon, the public library that holds bfinger's generic half.

License

Apache-2.0. One dependency is under the Open BSV License Version 5, whose grant is revocable and which limits use to the BSV blockchains; NOTICE explains, and LICENSE-THIRD-PARTY carries every license text.