How Document Anchoring creates tamper-evident proof
Document Anchoring binds a document's SHA-256 hash to a timestamp and organizational identity, proving the document existed in its exact form at a specific moment. The document itself never leaves your infrastructure.
Key principle: your document never leaves your infrastructure
You hash the document locally. Only the hash is submitted. Invoance never sees, stores, or processes the original document. This is a fundamental privacy guarantee - the proof is entirely hash-based. Your documents remain in your control while you gain cryptographic integrity verification.
$ sha256sum contract.pdfe3b0c44298fc1c149afbf4c8996fb924...Any cryptographic hash function produces a deterministic 256-bit fingerprint. Invoance operates entirely on hashes. The original document is never transmitted, stored, or analyzed by Invoance systems.
What you send
When anchoring a document, you submit the locally computed hash alongside optional context. The API endpoint accepts minimal required fields plus arbitrary metadata.
{
"hash": "e3b0c44298fc1c149afbf4c8996fb924...",
"filename": "contract-v3-final.pdf",
"reference": "Master Services Agreement, Acme Corp",
"metadata": {
"department": "legal",
"version": "3.0",
"signers": ["alice@acme.com", "bob@partner.com"]
}
}Your locally computed SHA-256 hash. This is the fingerprint of your document bytes.
Human-readable identifier for reference. Helps you locate the anchor record later.
Human-readable label describing the document. E.g., contract name, invoice number, or document title.
Arbitrary JSON context. Department, version, signers, cost center, any data you want associated with the anchor.
What happens on ingestion
When you submit a hash, Invoance executes a deterministic flow: receive, validate, deduplicate, sign, store, and confirm. Each step is atomic and immutable.
What you receive
The API response confirms the anchor with all required fields for future verification and audit purposes.
{
"id": "doc_x7y8z9a0",
"hash": "e3b0c44298fc1c149afbf4c8996fb924...",
"filename": "contract-v3-final.pdf",
"signature": "a1b2c3d4e5f6...",
"timestamp": "2025-03-15T14:32:07.123456Z",
"verification_url": "https://www.invoance.com/proof/document/doc_x7y8z9a0",
"status": "anchored"
}Unique anchor identifier. Use this to reference the anchor in your systems.
Echo of your submitted hash. Confirms the hash Invoance anchored.
Ed25519 signature over hash + timestamp. Verifier uses your tenant's public key to confirm authenticity.
ISO 8601 timestamp of ingestion. Proof that the document existed at this exact moment.
Public URL for third-party verification. No authentication required. Verifier can independently confirm integrity.
How verification works
Verification is straightforward: compute the hash of your original document and compare against the anchored hash. If they match, the document has not been altered since anchoring.
Duplicate detection
If a document with the same hash is submitted again for the same tenant, Invoance returns a 409 Conflict. This prevents accidental double-anchoring and enforces uniqueness of document proofs.
Conflict, document already anchored{
"error": "document_already_anchored",
"message": "This document hash was already anchored.",
"id": "doc_x7y8z9a0",
"timestamp": "2025-01-10T09:14:22.456789Z",
"verification_url": "https://www.invoance.com/proof/document/doc_x7y8z9a0"
}Why duplicate detection matters:
Compliance mapping
Document anchoring provides cryptographic integrity controls that address requirements across regulatory frameworks and audit standards.
CC6.1, CC6.6Logical access controls and system integrity verification. Anchoring provides immutable, independently verifiable proof of document integrity.
§164.312(c)(1)Access controls and audit logging for electronic records. Anchoring timestamps and cryptographically proves document integrity with audit trail.
A.12.4.1, A.18.1.3Event logging and protection of records. Append-only storage produces immutable audit trail; Ed25519 signatures prove non-repudiation.
Art. 5(1)(f)Integrity and confidentiality. Hash-based approach ensures data minimization, only the hash is submitted. Original document remains under your control.
Reg. (EU) 910/2014Invoance provides cryptographic foundation. Qualified timestamp authority (QTA) integration is on the roadmap for qualified electronic signatures.
Document anchoring uses the same cryptographic primitives as all Invoance records, SHA-256, Ed25519, and append-only storage. The proof is verifiable offline and independent of Invoance infrastructure.
How Document Anchoring Works, Invoance
Technical walkthrough of how Invoance Document Anchoring binds document hashes to timestamps and organizational identity using SHA-256, Ed25519, and append-only storage. Hash locally, submit the hash, and prove the document existed unchanged at a specific point in time.