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
Posts in “The Standard”
12 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
10 min read
What Goes on the Blockchain When You Make a Proof?
CardanoWall publishes a small proof record on Cardano, not your file. A hash-only proof exposes only a digest, while a sealed proof keeps the content encrypted off-chain — here's exactly what becomes public.
The StandardSecurity
9 min read
Is Label 309 Open Source?
Yes. Label 309 is an open Proof of Existence standard: the code is Apache-2.0, the spec is CC-BY-4.0, and anyone can implement it, fork it, run a gateway, and build products without asking CardanoWall for permission.
The StandardDevelopers
9 min read
What Is a Label 309 Gateway?
A Label 309 gateway is the publishing service that quotes, uploads, submits, confirms, and indexes Proof of Existence records through a standard API — while your keys stay on your device and proofs verify from public data.
DevelopersThe Standard
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
8 min read
Anchor C2PA Content Credentials to an Independent Timestamp
C2PA describes where media came from; Label 309 anchors the asset or its manifest to an independent public Cardano timestamp. Here is how the two layers fit together.
AI & ProvenanceThe Standard
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