Open Standard · W3C VC 2.0 Profile
Every data feed a W3C Verifiable Credential. Every source certified. Every signature independently verifiable — no trusted intermediary required.
In 2025, a speech analytics pipeline for a Brazilian pet company used large language models to evaluate call center conversations — looking for compliance failures, missed upsells, poor resolutions. Tens of thousands of calls per day, each one judged by AI.
It worked well. Then a question surfaced that couldn't be dismissed:
How does the AI know what it knows?
When the model said "the agent quoted the wrong price," it was comparing the agent's statement to product data it had been given. But that data had a source. The source had a timestamp. The timestamp had a context. And nowhere in that chain was there a single cryptographic guarantee that the data the model received was the data actually published, by the organisation that claimed to publish it, at the moment it claimed to have published it.
The model was reasoning over facts it could not verify. In a compliance context — where the output of the reasoning had real consequences for real people — that was a problem that could not be accepted.
The W3C Verifiable Credentials 2.0 specification solves the same problem CDS solves — cryptographically verifiable claims about a subject by an identified issuer — but for the entire ecosystem. CDS is a profile: a set of conventions for applying that infrastructure to real-time factual data.
Built on Tim Berners-Lee's four Linked Data rules. Every identity is a dereferenceable HTTP URI. Every event is valid JSON-LD. Every proof is independently verifiable with no dependency on signed-data.org's availability.
v0.1.0 — opaque strings
"content_type": {
"domain": "lottery.brazil",
"schema_name": "mega-sena.result"
},
"source": {
"id": "caixa.gov.br.loterias.v1"
},
"integrity": {
"signed_by": "signed-data.org"
}
v0.3.0 — W3C Verifiable Credential
"type": ["VerifiableCredential", "CuratedDataEvent"], "issuer": "https://signed-data.org", "credentialSubject": { "id": "https://signed-data.org/sources/...", "content_type": "https://signed-data.org/vocab/..." }, "proof": { "type": "DataIntegrityProof", "cryptosuite": "ecdsa-rdfc-2022" }
Each server is a FastMCP application exposing signed Brazilian data. Every tool response is a W3C Verifiable Credential issued by signed-data.org. Any consumer with the public key can verify independently.
mcp-lottery
lottery.brazil
Mega Sena, Lotofácil, Quina, Lotomania, Dupla Sena. 5 tools per game. Signed within seconds of each official draw.
Live
mcp-companies
companies.brazil
CNPJ lookup from the Receita Federal. Profile, partners (QSA), sanctions status. Signed at query time. 24h cache.
Live
mcp-finance
finance.brazil
SELIC, CDI, IPCA, PTAX from Banco Central. B3 quotes, FIIs, crypto via Brapi. Copom decisions.
Live
mcp-commodities
commodities.brazil
B3 agro futures (soja, milho, boi gordo, café, açúcar, etanol). CONAB weekly spot prices by state.
Live
mcp-weather
weather
Current conditions and forecasts via Open-Meteo. No API key. Signed every 30 minutes for Brazilian and international cities.
Live
mcp-sports
sports.football
Brasileirão, Libertadores, Copa do Brasil, Premier League, Champions League. Live scores and standings.
Live
mcp-gov-br
government.brazil
Portal da Transparência. Federal spending, contracts, procurement. CEIS+CNEP sanctions. API token in hand.
Live
mcp-ibge
demographics.brazil
Municipal population, GDP, IDEB, census microdata. Every Brazilian city, signed from IBGE's official API.
Live
mcp-processos
judiciary.brazil
CNJ DataJud judicial process lookup by CNPJ/CPF. Combined with mcp-companies: complete due diligence.
Live
mcp-currency
currency.brazil
BCB PTAX official rates, LATAM FX pairs, and real-time exchange conversion. Free, no API key required.
Live
mcp-equities
equities.brazil
Fundamentus data for B3 stocks: P/L, EV/EBITDA, dividend yield, DRE quarters, sector ranking.
Live
mcp-noticias
news.brazil
Signed Brazilian news headlines from GDELT. Every item delivered as a W3C Verifiable Credential.
Live
The W3C DataIntegrityProof (ecdsa-rdfc-2022) covers the canonical RDF serialisation of every event. Four properties hold independently of Wdotnet's availability.
01
The credentialSubject.id is the certified source URI — signed. Any modification to which API provided the data breaks the proof. MITM attacks on the upstream API produce invalid credentials.
"id": "https://signed-data.org/sources/api.bcb.gov.br.v1"
02
The payload is part of the signed canonical document. A single changed digit in SELIC rate, CNPJ status, or lottery dezenas causes proof verification to fail. Consumers detect tampering independently — no network call needed.
verifier.verify(credential) # → True or raises
03
The validFrom field is signed. Replay attacks — replaying a yesterday's SELIC rate as today's — are detectable. Consumers enforce freshness windows based on the signed timestamp.
"validFrom": "2026-04-25T18:00:03Z" # signed
04
The proof.verificationMethod resolves to a public key at signed-data.org/keys/1. The issuer document at signed-data.org/issuer carries the legal entity: Wdotnet, CNPJ 24.921.472/0001-45.
"issuer": "https://signed-data.org" # dereferenceable
Step 01
Wdotnet's ingestors fetch from certified APIs — BCB, Receita Federal, BrasilAPI, Caixa. Each source has a registered entry in the signed-data.org source registry with its URL, license, and certified domains.
Step 02
The raw response is fingerprinted (SHA-256). The payload is normalised, wrapped in a VerifiableCredential envelope, and signed with ECDSA P-256. The credential is stored and served via MCP tool endpoints.
Step 03
Your agent calls an MCP tool and receives a VerifiableCredential. Any W3C-compatible VC library verifies the DataIntegrityProof against the public key at signed-data.org/keys/1. Zero custom code. Zero trust in Wdotnet's availability.
v0.1.0 · Complete
Custom RSA-PSS signing. Opaque string identities. Python and TypeScript SDKs. mcp-lottery with 16/16 tests passing.
v0.2.0 · In progress
Every identity becomes a dereferenceable HTTP URI. Events are valid JSON-LD. Source registry published at signed-data.org/sources/. Achieves W3C 5-star open data rating.
v0.3.0 · Planned
CDS becomes a VC 2.0 profile. integrity block → DataIntegrityProof. RSA-4096 → ECDSA P-256. Any VC library verifies with zero custom code. did:web for issuer identity. 5-star open data with full VC ecosystem interoperability.
v0.4.0 · Vision
Issuer migrates to did:web:signed-data.org. VC Status List 2021 for credential supersession. OpenID4VC presentation protocol. SPARQL endpoint for querying stored credentials as RDF.
Hallucination is a hard error.
If an AI is going to act on a fact, someone must have signed that fact.