Chroma creates a cryptographically signed provenance record for a piece of work — documenting declared human authorship, declared AI involvement, and the integrity of the work at the moment the record is made. Here is exactly what happens, and what it can and cannot prove.
Chroma computes a SHA-256 hash of the work and of your provenance declaration. A hash is a fixed-length fingerprint: change a single pixel or character and the hash changes completely. The record stores the fingerprint, not the file.
The provenance record is signed with an Ed25519 private key. The signature proves the record was signed by the holder of that key and has not been altered since. Anyone holding the matching public key can verify the signature — no secret is required to verify.
The record's hash is submitted to OpenTimestamps, which aggregates many hashes into a Merkle tree and commits the tree's root into a Bitcoin transaction. Once the block confirms, the record's existence at that time is anchored to Bitcoin — independently checkable, with no need to trust KAMX. What is anchored is the record hash via the OpenTimestamps proof — not your media.
The provenance engine does not upload your original work. Only hashes and the declaration you choose to include leave your device. Verification runs entirely in your browser.
Note: this holds for the current engine and the in-browser verifier. Any future upload-based feature will keep hashing client-side, and this claim will be re-verified against uploads, previews, analytics and error reporting before it ships.
A recipient can recompute the fingerprint of the work, re-derive the record hash, check the Ed25519 signature, and confirm the Bitcoin anchor — offline, using only the public certificate. Nothing about KAMX needs to be trusted or online.
It proves
• the record has not been altered since it was signed;
• the signature is valid and made by the declared key;
• the submitted work matches the recorded fingerprint;
• the declaration existed at (or before) the anchored time.
It does not prove
• that every statement in the declaration is true;
• whether an undeclared work was or wasn't made with AI;
• copyright, ownership, or licensing of the work;
• that the declarant is who they claim to be beyond their key.
In short: Chroma verifies the integrity of a declaration and its cryptographic relationships — not the truthfulness of every real-world claim inside it. It is a provenance and disclosure tool, not an AI detector.