satsignal-blob 0.3.0

Anchor objects in S3 / R2 / GCS / Azure Blob to BSV via Satsignal. Files stay in your bucket; portable proof sidecars land next to them.

satsignal-blob

Anchor objects in S3 / R2 / GCS / Azure Blob to BSV via Satsignal. Files stay in your bucket; portable proof sidecars (.mbnt + .proof.json) land next to them.

Keep your files where they are. Satsignal gives them independent proof.

pip install satsignal-blob[s3]    # or [gcs], [azure], [all]

What it does

For each object under a bucket prefix, satsignal-blob streams the bytes through sha256, posts the digest (not the file) to Satsignal's POST /api/v1/anchors, and writes two sidecar objects next to the original:

sibling	what it is	who uses it
contract.pdf.mbnt	full evidence bundle (zip) — txid, canonical doc, miner acceptance, BSV chain anchor	anyone who needs to verify the receipt offline against a public BSV explorer
contract.pdf.proof.json	one-page summary — sha256, txid, receipt URL, bundle URL, timestamp	humans, dashboards, grep / jq pipelines

The original contract.pdf is untouched. The file bytes never leave your bucket — Satsignal only sees the sha256.

CLI quickstart

Vocabulary: folder is the canonical public name; matter is a frozen legacy alias and keeps working forever. The CLI accepts --folder alongside --matter; the library accepts folder_slug= alongside matter_slug=. Either --folder or --matter is required (legacy invocations that pass --matter are unaffected). If both are set to different values the command fails loudly; equal or single is fine. The .proof.json sidecar carries both folder_slug and matter_slug (and proof_id/bundle_id, proof_url/receipt_url). Since 0.3.0 the HTTP request to the Satsignal API sends the canonical folder_slug key (self-hosted servers need a 2026-06+ build, which accepts both).

export SATSIGNAL_API_KEY=sk_...

# Anchor every PDF under a prefix, cap at 50 attempts.
satsignal-blob anchor s3://my-bucket/contracts/2026/ \
    --folder contracts-2026 \
    --include '*.pdf' \
    --max-files 50

# Dry-run first to preview hashes + plan without firing any anchors:
satsignal-blob anchor s3://my-bucket/contracts/2026/ \
    --folder contracts-2026 --include '*.pdf' --dry-run

A successful run prints one line per object plus a summary on stderr:

[OK]   s3://my-bucket/contracts/2026/a.pdf  sha=ab1234567890 bundle=87f9c2b4… txid=e7c4f1…
[OK]   s3://my-bucket/contracts/2026/b.pdf  sha=cd5678901234 bundle=2a91b3e5… txid=e7c4f1…
[SKIP] s3://my-bucket/contracts/2026/c.pdf  (.mbnt sidecar exists; --force to re-anchor)
satsignal-blob: anchored=2 duplicate=0 skipped_existing=1 skipped_sidecar=0 failed=0

Pass --json to emit one JSON object per line — pipe through jq / fluentd / anything line-oriented.

Supported backends

satsignal-blob resolves URIs through fsspec. Install the optional dep that matches your storage:

storage	URI scheme	install extra	backend
AWS S3 / MinIO / Wasabi / B2 / Cloudflare R2	s3://	pip install satsignal-blob[s3]	s3fs
Google Cloud Storage	gs://	pip install satsignal-blob[gcs]	gcsfs
Azure Blob Storage	az://	pip install satsignal-blob[azure]	adlfs
Local filesystem	/path/ or file:///	(none)	built-in

Cloudflare R2 is S3-compatible — use s3:// and configure the AWS_ENDPOINT_URL_S3 env var to point at your R2 endpoint.

Library API

from satsignal_blob import anchor_prefix

for outcome in anchor_prefix(
    "s3://my-bucket/contracts/2026/",
    api_key="sk_...",
    folder_slug="contracts-2026",
    include=["*.pdf"],
):
    if outcome.status == "anchored":
        print(outcome.receipt_url)

Or a single object:

from satsignal_blob import anchor_object

result = anchor_object(
    "s3://my-bucket/contracts/2026/contract.pdf",
    api_key="sk_...",
    folder_slug="contracts-2026",
)
print(result.txid, result.receipt_url)

Event-driven (S3 → Lambda)

For real-time anchoring on every PUT, wire an S3 ObjectCreated:* event to a Lambda that calls anchor_object. Copy examples/lambda_handler.py into a Python 3.11 Lambda, set three env vars, and you're done:

import os, urllib.parse
from satsignal_blob import anchor_object

API_KEY = os.environ["SATSIGNAL_API_KEY"]
WORKSPACE_SLUG = os.environ["SATSIGNAL_WORKSPACE_SLUG"]
FOLDER_SLUG = os.environ["SATSIGNAL_FOLDER_SLUG"]


def lambda_handler(event, context):
    results = []
    for record in event.get("Records", []):
        bucket = record["s3"]["bucket"]["name"]
        key = urllib.parse.unquote_plus(record["s3"]["object"]["key"])
        if key.endswith((".mbnt", ".proof.json")):
            continue  # don't anchor sidecars
        outcome = anchor_object(
            f"s3://{bucket}/{key}",
            api_key=API_KEY,
            folder_slug=FOLDER_SLUG,
        )
        results.append({"key": key, "status": outcome.status,
                        "bundle_id": outcome.bundle_id})
    return {"results": results}

Same pattern works for Cloud Functions (GCS finalize) and Azure Functions (blob trigger) — just swap the scheme and the event shape.

What this proves (and what it doesn't)

A Satsignal anchor over sha256(file) proves:

• The operator of this Satsignal workspace knew this sha256 by the block time of the on-chain anchor. Anyone with the file can later recompute the sha and verify against the chain entry — without trusting Satsignal or your storage provider.

It does not prove:

• That the file existed before the anchor. The chain only records when the sha entered the ledger.
• The identity of whoever uploaded it. The receipt is "this sha was anchored by this workspace at this time" — not "this person did it."

For workflows that need before-the-anchor existence (e.g. press- embargo proofs), pair satsignal-blob with a commit-reveal flow via satsignal-cli or the /commit_reveal.py helper.

Threat model

• sha-only. File bytes never leave your process. The Satsignal API only sees the digest + size + optional label + filename.
• Untrusted attribute fields. label and filename are clipped server-side at 256 chars and validated for control substrings. Still — don't put secrets in either.
• Fail-open per object. One file's API failure does not abort the walk. The exit code is 1 if any file failed; the per-file error is in the JSON output.
• No bytes on chain. Satsignal never anchors file contents — only the digest. This is by design and is not a config option.

Related packages

• satsignal-cli — general-purpose anchor + verify CLI; can verify any .mbnt file written by satsignal-blob.
• satsignal-mcp — MCP server exposing the same 5 primitives to MCP-aware agents.
• satsignal-otel — anchor OpenTelemetry spans (failed evals, release gates).
• satsignal-action — GitHub Action: anchor build artifacts on every release.

License

MIT