cardanowall-sdk — the Python SDK for Label 309 Proof-of-Existence

A byte-identical parity twin of the TypeScript @cardanowall/sdk-ts: a standalone Label 309 verifier, a gateway-agnostic HTTP client, off-host signing, the structural validator, and the raw-seed identity surface — all in Pythonic, mypy-strict form.

What it is

Label 309 is an open standard for anchoring a content hash on the Cardano blockchain under transaction metadata label 309, so anyone with the transaction reference can later prove "this content existed on or before block time T" — without trusting any server, domain, or issuer identity.

cardanowall-sdk is the Python member of a five-package family. It bundles the standalone verifier (the three verifier roles), the gateway-agnostic HTTP client for publishing and reading records against any Label 309 service, the structural validator over canonical-CBOR record bytes, the sealed-PoE wrap/unwrap primitives, and raw-seed identity helpers. Its cryptographic core under cardanowall._crypto is a byte-for-byte parity twin of the TypeScript @cardanowall/crypto-core and Rust references: every encoder, digest, signature, and KEM is validated against the same shared known-answer vectors, so a record produced or verified here is bit-identical to one produced or verified by any sibling SDK. The whole package is type-checked under mypy --strict.

Install

pip install cardanowall-sdk

Requires Python 3.11+. The SDK is async-canonical (built on httpx.AsyncClient); every client method returns a coroutine. For synchronous use, wrap calls in asyncio.run(...).

Quick start

Verify any Label 309 record — standalone, no service dependency

verify_tx is the full public/recipient verifier. Given a Cardano transaction hash it fetches the metadata from a public explorer, runs structural validation, verifies record signatures, recomputes Merkle roots, and returns a discriminated report. No issuer server is contacted.

import asyncio
from cardanowall import verify_tx, VerifyTxInput

report = asyncio.run(verify_tx(VerifyTxInput(tx_hash="<64-char hex tx hash>")))
print(report.verdict)  # "valid" | "pending" | "unverifiable" | "failed"

Validate raw record bytes — pure, no I/O

validate_poe_record (re-exported from poe_standard) is a pure function over canonical-CBOR bytes. It returns a discriminated result: ValidateOk carries the typed record, ValidateFail carries the structured issue list.

from cardanowall import validate_poe_record
from cardanowall.poe_standard import ValidateOk

result = validate_poe_record(record_bytes)  # bytes
if isinstance(result, ValidateOk):
    print(result.record["v"])               # the parsed record
else:
    for issue in result.issues:
        print(issue.code, issue.path)        # e.g. "SCHEMA_MISSING_REQUIRED"

Publish with the gateway-agnostic client

The client targets any Label 309 gateway. base_url is required and used verbatim — it is the full versioned base, including the API version segment (e.g. https://gateway.example.com/api/v1); each request appends only a resource suffix (/records, /poe/quote, …) to it. api_key is an opaque bearer token forwarded as Authorization: Bearer <key> with no format assumptions. gateway.example.com below is only one example deployment — substitute any conformant gateway, including a self-hosted one.

import asyncio
from cardanowall import Label309Client, signer_from_seed

async def main() -> None:
    signer = signer_from_seed(seed=b"\x00" * 32)  # 32-byte seed; SDK never sees the private key persisted
    async with Label309Client(
        base_url="https://gateway.example.com/api/v1",
        api_key="<opaque-bearer>",
    ) as client:
        quote = await client.poe.quote(
            record_bytes=200, recipient_count=0, file_bytes_total=0,
        )
        out = await client.poe.publish_content(
            content="hello world",            # also accepts bytes
            quote_id=quote["quote_id"],
            signer=signer,
        )
        print(out["id"], out["status"])

asyncio.run(main())

The hash-only flows (publish_content, publish_prehashed) and the low-level publish / publish_batch take a caller-supplied quote_id: request a quote first (it locks the USD price for a 15-minute TTL) and pass the returned quote_id to the call. The quote is consumed atomically with the record insert. publish_content also co-hashes the content under several algorithms (hash_algs=["sha2-256", "blake2b-256"], bound into one item), and both content flows accept optional uris (already-pinned ar:// / ipfs:// content mirrors) and a supersedes link to an earlier record.

The internally-quoting helpers price their exact record shape themselves and take no quote_id: publish_merkle, and the sealed flow's submit_sealed / publish_sealed. They quote, enforce an optional max_usd_micros cap, and refresh the price lock if a slow upload outlived it. quote_prepared_seal returns a price preview a caller may hand to submit_sealed via its quote argument; a stale preview is silently re-quoted.

Publish a sealed PoE — encrypted to one or more recipients

publish_sealed is the one-shot sealed flow: it seals every item to the recipient public keys (age-style sealed envelope), quotes internally, uploads each ciphertext to Arweave, and publishes the multi-item record. items is a list of bytes/str (one sealed item each — a bare str is rejected, so wrap a lone value in a list); recipients are raw KEM public keys (the post-quantum X-Wing hybrid by default, 1216 bytes each). It takes no quote_id — pass max_usd_micros to cap the internally-fetched price. The result is a SealedSubmission (the gateway response, the published record_bytes, and the ar:// uris).

import asyncio
from cardanowall import Label309Client, derive_keys_from_seed

async def main() -> None:
    # In practice the recipient shares this key; here we derive it from a seed.
    recipient_pub = derive_keys_from_seed(b"\x11" * 32)["mlkem768x25519"]["public_key"]
    async with Label309Client(
        base_url="https://gateway.example.com/api/v1",
        api_key="<opaque-bearer>",
    ) as client:
        submission = await client.poe.publish_sealed(
            items=[b"secret report", "second attachment"],  # a LIST, one sealed item each
            recipients=[recipient_pub],                      # X-Wing public keys (1216 bytes)
            max_usd_micros=500_000,                          # refuse above $0.50
        )
        print(submission.response["id"], submission.response["status"])
        print(submission.uris)   # the ar:// URI of each item's ciphertext

asyncio.run(main())

Two-phase sealed publish with crash-safe resume

For flows that must survive a crash (CI jobs, multi-GB ciphertexts), split the sealing from the network round-trips. seal_prepare is pure and offline: it hashes and encrypts every item and returns a PreparedSeal that serializes to the portable prepared_seal_json_v1 artifact (to_json() / from_json(), the latter re-verifying its fingerprint). Persist that artifact, then submit_sealed quotes, uploads, and publishes. If submit_sealed fails after a paid upload, the SubmitSealedError carries validated UploadReceipts — persist them and pass them back as uploaded on the retry, and the already-uploaded ciphertexts are never paid for twice.

import asyncio
from cardanowall import Label309Client, derive_keys_from_seed
from cardanowall.client import PreparedSeal, SubmitSealedError, seal_prepare

async def main() -> None:
    recipient_pub = derive_keys_from_seed(b"\x11" * 32)["mlkem768x25519"]["public_key"]

    # Phase 1 — pure and offline: no network, nothing secret leaves the host.
    prepared = seal_prepare(items=[b"page one", b"page two"], recipients=[recipient_pub])

    # Persist the portable artifact; from_json re-verifies its fingerprint on load.
    prepared = PreparedSeal.from_json(prepared.to_json())

    async with Label309Client(
        base_url="https://gateway.example.com/api/v1",
        api_key="<opaque-bearer>",
    ) as client:
        # Phase 2 — online: quote → upload each ciphertext → publish.
        try:
            submission = await client.poe.submit_sealed(prepared=prepared, max_usd_micros=1_000_000)
        except SubmitSealedError as err:
            # Resume: in a real flow you persist err.uploads (and the artifact)
            # across process runs, then replay with the receipts — storage is
            # charged only once.
            submission = await client.poe.submit_sealed(
                prepared=prepared, max_usd_micros=1_000_000, uploaded=err.uploads
            )
        print(submission.response["id"], submission.uris)

asyncio.run(main())

Publish a passphrase-sealed PoE

To deliver to someone who has no Label 309 identity, seal to a shared passphrase instead of recipient keys: anyone who knows it can open the record, with no delivery address involved. The passphrase surface mirrors the recipient one — the pure passphrase_seal_prepare(...) feeding submit_passphrase_sealed(...) (with quote_prepared_passphrase_seal(...) for a preview and UploadReceipt resume), and publish_passphrase_sealed(...) as the one-shot wrapper. Read the passphrase from the environment or a prompt, never a source-embedded literal:

import asyncio
import os
from cardanowall import Label309Client

async def main() -> None:
    passphrase = os.environ["SEAL_PASSPHRASE"]
    async with Label309Client(
        base_url="https://gateway.example.com/api/v1",
        api_key="<opaque-bearer>",
    ) as client:
        submission = await client.poe.publish_passphrase_sealed(
            items=[b"quarterly numbers"],            # a LIST, one sealed item each
            passphrase=passphrase,
            hash_algs=["sha2-256", "blake2b-256"],   # co-hash the item under both
            max_usd_micros=500_000,                  # refuse above $0.50
        )
        print(submission.response["id"], submission.uris)

asyncio.run(main())

A recipient opens it by passing the passphrase to verify_tx — a DecryptionPassphrase credential joins the same keyring as any recipient key and is tried against every sealed item.

API overview

Verifier (cardanowall.verifier, top-level re-exports)

The three verifier roles, all reachable through verify_tx:

• Structural validator — validate_poe_record(bytes): pure, no I/O, no crypto. Returns ValidateOk | ValidateFail.
• Public verifier — verify_tx(VerifyTxInput(...)): fetches metadata, runs structural validation, verifies record signatures, recomputes Merkle roots.
• Recipient verifier — verify_tx with a decryption input (an X25519 / X-Wing secret): additionally decrypts a sealed PoE and recomputes plaintext hashes.

Outbound HTTP is funnelled through a single FetchOutbound so a caller can inject a custom transport (default_fetch_outbound is the built-in); a deny-host floor (DENY_HOSTS_DEFAULT) blocks single-implementer domains (including cardanowall.com) to prove service-independence. fetch_item_ciphertext fetches sealed-PoE ciphertext bounded by DEFAULT_OUTBOUND_MAX_BYTES. detect_conformance_profile reports a record's conformance profile.

Gateway-agnostic client (cardanowall.client)

Label309Client(base_url=..., api_key=..., http_client=...) exposes four namespaces:

• client.poe — quote(...), publish_content(...) (with hash_algs co-hashing + optional uris), publish_merkle(...) (one-call high-level flows), the two-phase sealed surface — the pure seal_prepare(...) (to recipients) / passphrase_seal_prepare(...) (to a shared passphrase), both from cardanowall.client, feeding quote_prepared_seal(...) / submit_sealed(...) and quote_prepared_passphrase_seal(...) / submit_passphrase_sealed(...), with publish_sealed(...) / publish_passphrase_sealed(...) as the one-shot wrappers — plus the low-level uploads(...), publish(...), publish_batch(...) wire-shape methods. A PreparedSeal serializes to the portable prepared_seal_json_v1 artifact (to_json() / from_json()), so a failed publish retries from persisted material and UploadReceipts without ever re-encrypting.
• client.records — get(tx_hash) to read a record by transaction hash.
• client.inbox — sealed-PoE discovery for a recipient.
• client.account — balance() and account-scoped reads.

All client failures raise typed errors inheriting from Label309HttpError: RateLimitedError, InsufficientFundsError, QuoteExpiredError, QuoteAlreadyConsumedError, QuoteNotFoundError, FxStaleError, IdempotencyConflictError, UnauthenticatedError, InsufficientScopeError, RecordNotFoundError, MalformedCborError, InvalidBodyError, PartialUploadError, and others. InvalidClientConfigError is raised eagerly if base_url is missing.

Wire format (cardanowall.poe_standard)

• encode_poe_record(record) / encode_record_body_for_signing(record) — canonical-CBOR encoders.
• validate(bytes) (re-exported as validate_poe_record) — the structural validator; ValidateOk / ValidateFail / ValidationIssue / ErrorCode / SEVERITY.
• PoeRecord and the schema TypedDicts (Item, Slot, EncryptionEnvelope, MerkleCommit, …).

Primitives, identity, and signing

• cardanowall.hash — sha2_256, blake2b_256, dual_hash, dual_hash_stream.
• cardanowall.merkle — merkle_sha2_256_root, merkle_sha2_256_inclusion_proof, merkle_sha2_256_verify_inclusion, encode_leaves_list / decode_leaves_list.
• Sealed PoE — ecies_sealed_poe_wrap / ecies_sealed_poe_unwrap.
• Recipients — encode_age_x25519_recipient, encode_age_xwing_recipient, parse_age_recipient.
• Seed derivation — derive_ed25519_keypair_from_seed, derive_x25519_keypair_from_seed, derive_mlkem768x25519_keypair_from_seed.
• Seed identity — derive_keys_from_seed, recipients_from_seed, signer_from_seed, recipient_secret_keys_from_seed, decrypt_sealed_from_seed.
• Webhooks — verify_webhook_signature, build_webhook_signature_header, sign_webhook_payload.
• Stable identifiers — encode_prefixed_id / decode_prefixed_id, Crockford base32 codecs, and the ID prefix/pattern constants.

See src/cardanowall/__init__.py for the exhaustive __all__.

Raw-seed identity, end to end

A developer holding a 32-byte seed can sign, address recipients, and decrypt without any account envelope. The hybrid post-quantum KEM (X-Wing, ML-KEM-768 + X25519) is exposed alongside the classical X25519 path.

from cardanowall import (
    derive_keys_from_seed,
    recipients_from_seed,
    signer_from_seed,
)

seed = b"\xff" * 32
keys = derive_keys_from_seed(seed)            # ed25519 / x25519 / mlkem768x25519 keypairs
recipients = recipients_from_seed(seed)       # {"age": "age1...", "age1pqc": "age1pqc..."}
signer = signer_from_seed(seed)               # a path-1 Signer for client.poe.publish_*

Off-host signing

If you build the canonical-CBOR record yourself and sign on a separate host (KMS, HSM, an air-gapped machine), build_to_sign(record) produces the exact bytes to sign; the SDK never needs the private key.

from cardanowall import build_to_sign
from cardanowall.poe_standard import PoeRecord

record: PoeRecord = {"v": 1, "items": [{"hashes": {"sha2-256": digest}}]}
to_sign = build_to_sign(record)   # hand these bytes to your external signer

Cross-implementation parity

cardanowall-sdk is a byte-identical parity twin of @cardanowall/sdk-ts and the cardanowall Rust crate. The canonical-CBOR encoder, the structural validator and its error codes, the COSE_Sign1 signing input, the sealed-PoE envelope, the Merkle leaves-list codec, and the seed-derived recipient strings are all pinned to the same shared known-answer vectors mirrored byte-for-byte across all three languages. This guarantees that:

• a record encoded in Python produces the exact bytes that go on chain in TS/Rust;
• a record that validates here validates identically everywhere (same verdict, same error codes);
• an age1... / age1pqc... recipient string derived from a seed is identical across SDKs, so cross-SDK senders and recipients interoperate.

Standard and service independence

The verifier proves a PoE from three inputs only: the transaction metadata, optionally the content bytes, and a public blockchain explorer. No issuer server is required at any step. The default deny-host list explicitly blocks single-implementer domains during verification, and the conformance suite runs with that list active — so a record is provably verifiable without the gateway that published it.

A bundled conformance runner verifies a transaction from the command line:

cardanowall-sdk-conformance <tx-hash>
# or:
python -m cardanowall.conformance <tx-hash>

Exit codes: 0 valid, 1 failed (integrity), 2 failed (network), 3 pending, 4 CLI input error.

Relation to the other packages

• @cardanowall/crypto-core — closed-catalogue cryptographic primitives (hash, KDF, signature, KEM, AEAD, CBOR, COSE, sealed-PoE, discovery, Merkle, recipient encoding, seed derivation). The portable building blocks.
• @cardanowall/poe-standard — the Label 309 wire-format library: record schema, canonical-CBOR encoder, pure structural validator, and error-code catalogue.
• @cardanowall/sdk-ts — the browser + Node TypeScript SDK; the reference this package mirrors.
• cardanowall-sdk (this package) — the Python SDK; the byte-parity twin.
• cardanowall (Rust crate) — the Rust SDK; the byte-parity twin in Rust. (The cardanowall CLI binary is a separate crate built on it.)

License

Apache-2.0 — see LICENSE.