2 min read
Label 309 Is Now CIP-0190
The Proof of Existence standard we wrote for Cardano has been accepted into the official CIP repository as CIP-0190. Here is what that means, what it does not mean, and what comes next.
Announcements
Posts tagged “proof-of-existence”
7 min read
Prove One File from a Merkle Batch: The Inclusion Certificate
After many file hashes are published under one Merkle root on Cardano, an inclusion certificate is a small downloadable file that proves one specific file was part of that batch — checkable in your own browser, with no trust in CardanoWall, forever.
The StandardGuides
9 min read
CardanoWall Returns, Built on Label 309
CardanoWall is relaunching as a Proof of Existence service built on Label 309, an open, vendor-neutral record format for Cardano metadata. Hash, sign, seal, and share content, then verify it without trusting our servers.
Announcements
10 min read
What Is Proof of Existence?
Proof of Existence shows that exact data existed no later than a public timestamp — without publishing the private file itself. Here's how it works and what it does and doesn't prove.
The StandardGuides
11 min read
How Label 309 Works
Label 309 writes a Proof of Existence into Cardano transaction metadata: a content hash first, plus optional signatures, sealed payloads, recipient key slots, and Merkle batches. Here is how each layer works and how anyone verifies it.
The Standard
10 min read
Hash, Sign, Seal, Share: The Four Levels of a CardanoWall Proof
CardanoWall builds proofs in four layers: a plain hash timestamp, an optional signature, an encrypted sealed copy, and private delivery to specific recipients. You use only the layers a situation needs.
The StandardGuides
9 min read
One Record for Thousands of Files: Merkle Batching
A Merkle root lets one Label 309 record commit to thousands or millions of file hashes, then prove any single item later with a small inclusion proof — without putting every item on chain.
The StandardDevelopers
9 min read
How to Prove Training Data Without Revealing It
Commit a private dataset snapshot to a hash or Merkle root and publish one timestamped proof. The data stays private; later you can selectively prove a file, row, or version was in the committed set.
AI & ProvenanceSecurity
9 min read
Legal Evidence and E-Discovery: Timestamping Documents and Discovery Exports
How to use Label 309 Proof of Existence to prove a document or discovery export existed by a public time and still matches its original bytes — and where that proof stops and legal process begins.
Compliance & Legal
10 min read
Build a Verifiable Security Incident Timeline Without Going Public
How a security team can timestamp and seal incident evidence as it is collected — a durable, independently verifiable timeline that proves what existed when, without publishing sensitive details.
SecurityCompliance & Legal
8 min read
Creative Proofs for Artists
Hash your source files, drafts, prompts, exports, or whole project folders and publish a timestamped Label 309 proof that they existed by a given time — without making the work public.
AI & ProvenanceGuides
9 min read
Publish Your First Proof of Existence on Cardano
Your first Label 309 proof can be a hash-only record: hash a file, get a price quote from a gateway, publish the digest on Cardano, and keep the transaction hash. Here is the full workflow.
GuidesDevelopers
11 min read
What a Proof of Existence Does Not Prove
A Proof of Existence shows that exact bytes existed by a public time. It does not, on its own, prove ownership, truth, authorship, who was first, legality, or admissibility.
The StandardGuides
7 min read
Proof of Existence vs a Timestamp Authority: which trust model do you need?
Both bind data to a point in time, but a Timestamp Authority roots trust in a named provider's key, while a Label 309 Proof of Existence roots it in public Cardano consensus. Here's how to choose.
The StandardCompliance & Legal
8 min read
Proof of Existence vs C2PA: how do they fit together?
C2PA describes the provenance of a media asset; Label 309 anchors a timestamped commitment to its bytes on Cardano. Here is what each one proves, and why most workflows want both.
The StandardAI & Provenance
7 min read
Proof of Existence vs Sigstore: do you need both?
Sigstore signs software artifacts and logs the event publicly; Label 309 adds an independent blockchain time anchor over your whole release evidence. They solve different problems and work well together.
The StandardDevelopers
9 min read
Proof of Existence vs OpenTimestamps: which timestamping fits your work?
OpenTimestamps is excellent for bare, Bitcoin-anchored timestamps. Label 309 adds a Cardano-native proof record with signatures, sealing, recipients, and Merkle batching — here is how to choose.
The Standard