Live · proof layer
VCC — Verifiable
Calculation Certificates.
A VCC turns a calculation into a cryptographic receipt that records which formula ran, at which version, on which inputs — signed and content-addressed, so anyone can check its integrity and provenance offline, without trusting this site.
What a VCC proves
- who issued the receipt (Ed25519 signature + published keys)
- which formula and version ran (manifest digest)
- which validated inputs were used
- which outputs were produced, with declared units and rounding
- which versioned datasets were consumed
- that nothing changed after signing (content-addressed statement)
- when possible, that re-running the formula reproduces the outputs
What it deliberately does not prove
- that the inputs are true
- that the formula is legally or economically appropriate for your purpose
- that the result is advice, a decision, or a professional opinion
- regulatory compliance of any kind
- that a valid signature equals an independent audit
That is why verification reports four separate axes — authentic, intact, reproducible, trusted — and never a single “verified” stamp.
How it works
From calculation to checkable proof.
Deterministic execution — your validated inputs run through a pure, versioned formula.
Canonical statement — inputs, outputs, formula digest and datasets — one unambiguous JSON (RFC 8785).
Content-addressed id — the receipt id is the hash of its own content: change a byte, change the id.
Signature — Ed25519 over a DSSE envelope, with the issuer keys published at a well-known URL.
Independent verification — anyone re-checks signature and integrity offline; formulas in the open registry can be re-run and diffed.
Get started
Issue your first VCC.
Add ?certify=1 to any certifiable tool endpoint. Without the flag the response is byte-identical to the legacy API; with it, the same deterministic calculation comes back with a signed receipt attached.
curl -X POST "https://calcfleet.com/api/v1/tools/personal-loan-calculator?certify=1" \
-H "content-type: application/json" \
-d '{"principal":10000,"annualRatePct":9.5,"termMonths":36,"originationFeePct":2}'The response carries your result unchanged, plus a certificate: a human-readable statement and the canonical envelope— a DSSE envelope whose payload is the RFC 8785 canonical statement, signed with Ed25519. The envelope is the receipt: store and share that. If certification is ever unavailable, you still get your result, plus certificate: null and an explicit reason — it never blocks the calculation.
Access, honestly: the call above runs as-is against calcfleet.com/api/v1 — no key required (an optional Authorization: Bearer cf_… key raises the rate limits; see how API access works). You can also issue over MCP: the three pilot tools accept certify: true with no key — free during launch.
Certification is live on 4 pilot calculators:
For AI agents
An agent that quotes a number can attach proof of where it came from — formula, version, inputs — instead of asking you to trust the transcript.
For software
Log the receipt, not a screenshot. Any pipeline can re-verify results years later, offline, byte for byte.
For compliance-minded teams
Integrity and reproducibility become checkable properties. What a VCC does not prove is stated just as clearly.
Open core, managed edges
One open specification. Four ways to use it.
VCC is an experimental open specification for verifiable calculation receipts, with CalcFleet as its first reference implementation. Read the specification.
Free, forever
Open specification
An experimental open specification (v0.2), with CalcFleet as its first reference implementation. The certificate format, numeric profile and threat model are documented; L1 verification is plain DSSE + Ed25519 + RFC 8785 against published keys — anyone can check a receipt offline, without ever calling this site.
Free, forever
Free public verification
Paste any receipt on the verify page, or POST its envelope to the public verify API — no account, rate-limited. Both report the four axes separately, never a single “verified” stamp.
Built with design partners
Managed issuance
Certified calculations at volume: issuance quotas, hosted receipt storage and retention windows shaped around how long your records need to stay checkable. Not self-service yet — we scope it together.
Built with design partners
Enterprise trust infrastructure
A private formula registry, receipts issued under your own issuer identity, and BYOK / KMS-backed signing so the key never leaves your control. Designed case by case with early partners.
Managed issuance and enterprise trust infrastructure are early offers we are shaping together with design partners — there is no self-service checkout and no published pricing yet. The open specification and public verification stay free either way, and nothing here is a compliance guarantee.
Rollout status — honest edition
VCC is live in production, signing with a published key, on 4 pilot formulas (personal-loan, compound-interest, home-affordability, tiered-commission), behind an explicit certify flag on the API and MCP. The certificate format, test vectors and threat model are public in the repository docs; the rest of the fleet migrates formula by formula.
A receipt demonstrates the integrity, provenance and — when available — the technical reproducibility of a calculation. It does not prove that inputs are true, that a formula fits a specific purpose, or that a result constitutes professional advice or a regulatory certification.