The record format
In developmentTARC: records anyone can check.
TARC, the Trusted Agentic Record Container, is the open file format Arkhon records are written in. It is built for a reader who has no reason to trust the system that wrote the record. They can check it themselves, offline, with open tools.
This page is an overview of what TARC records show and where the guarantees end.
Why a format, and not just a log
A log is usually written to be read by its owner. In a dispute, the reader is somebody else: an auditor, a regulator's technical expert, the other side's engineer. They have no reason to take the owner's word for it. TARC is designed for that reader.
- 01
Tamper-evident, not tamper-proof
Nothing can stop someone from altering a file. TARC makes alteration, deletion and reordering detectable, and says plainly that it does not make them impossible.
- 02
Checkable without us
Checking a record needs the files, an open verifier and the public keys the checker chooses to trust. Arkhon doesn't need to be reachable or to cooperate.
- 03
Honest about its limits
A record shows that data hasn't changed since it was committed. It does not show that the data is true. The format states where its guarantees end.
How a record holds together
A TARC record is built so that each part depends on the parts before it. Change, remove or reorder anything, and the mismatch shows.
Each piece commits to the one before
Every piece is tied to the one before it. Change, remove or reorder any piece and everything after it stops matching. A signature on a later piece covers everything before it.
- Piece 0Sample
- Links to
- start of record
- Its hash
- 4bbbcb52…
- Piece 1Sample
- Links to
- 4bbbcb52…
- Its hash
- 459dd958…
- Piece 2Sample
- Links to
- 459dd958…
- Its hash
- d3c711b6…
- Piece 3Sample
- Links to
- d3c711b6…
- Its hash
- 6a91ae23…
An illustration of the idea. A real record carries more than this.
Built to hold up
- Never editedOnce written, a record isn't changed. A tool that converts a file writes a new one.
- Safe to crashA file is readable up to its last intact part. A damaged end is reported, never silently dropped.
What a check can show
Trust is layered. Some checks need no keys at all, so someone who distrusts everyone involved can still run them. Others need a public key, or a time authority's certificate.
01Not altered
Needs: Nothing
The recorded content is exactly what was written.
02Nothing removed or reordered
Needs: Nothing
No part was deleted, moved or cut off.
03Who committed it
Needs: A public key
The signer named in a certificate.
04When it existed
Needs: A time authority's public certificate
That the record existed in this exact form at a given time.
05Nothing left out
Needs: A public key
That no whole part of the recording was omitted.
An unsigned record isn't "somewhat attributed". It is unattributed. Which checks apply to a record is written into it, so quietly dropping one shows.
How a record is checked
Anyone with the files can check a record, offline. The checker needs the files, an open verifier and the public keys it has chosen to trust. It doesn't need Arkhon, the signer or a network connection.
The checker works only from what is in the file and the keys it is given. It recomputes what it can, compares, and reports every difference.
What the checker reports
For each record, one of four results, best to worst.
- 1Intact, signer verifiedThe signer is established.
- 2Intact, unsignedThere is no signature.
- 3Intact, signer unverifiedThe signer couldn't be established.
- 4ImpairedSomething was altered, removed or damaged.
An intact record whose signer can't be established is never reported as simply "valid". The newest part after the last signature is reported as an unsigned tail, with its exact range. A failure is a finding: it is reported, never repaired or hidden. A break names the gap, which is the difference between an honest gap and concealed tampering.
Who signed, and who vouches for that
A signature shows that the holder of a private key committed to this exact content. A certificate ties that key to a named signer.
The evidence travels with the record
What a checker needs to see who signed comes with the record, so it doesn't need to ask anyone.
Keys can be revoked
A key that is lost or compromised can be revoked from a stated time. Earlier records stay checkable, and an independent time stamp shows which signatures came before.
What TARC does not prove
The specification lists its non-claims explicitly. These are the main ones.
- That the data is true. A signature authenticates the recorder, not reality.
- That the software upstream of the point where signing happens was honest or correct. That point is the capture boundary. It is trusted by assumption, and a deployment that makes evidentiary claims has to state where it sits.
- That sensors weren't fooled or inputs spoofed before capture.
- When a record was made, unless it carries an independent time anchor. A signature commits to content, not to a time.
- That everything that should have been recorded was recorded.
- That a whole recording wasn't replaced from scratch. That is only detectable against something held elsewhere, such as an independent time anchor.
- That records are tamper-proof. They are tamper-evident.
Where trust remains
If one party issues the certificates and stores the records, that party is trusted for who signed and for completeness. For everyday integrity that is fine. In a dispute, a skeptic will ask what stops that party and the signer from colluding. Independent time stamps limit what such a party could rewrite, but they don't make its statements independent. We say so plainly.
What a record can carry
TARC doesn't judge the data it holds. It seals what it is given.
Agent activity
Traces, metrics, logs and messages from AI agents.
Robots and sensors
Images, audio, sensor data and robot messages.
Compressed, optionally encrypted
Records can be compressed, and encrypted at rest.
At a glance
- Open
- The format and its verifier are open, so a record can be checked without Arkhon.
- No blockchain
- No ledger, consensus or token. One producer writes one ordered sequence, so there is nothing to agree on.
- Separate from transport
- TARC is the format. The protocol that carries records from an agent to a recorder is separate and proprietary.
Links to the specifications and the verifier will appear here when each is public.
Want to record with it?
TARC is the format. Arkhon builds the recorder that writes it. Early access is open, and I read every response personally.
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