Section 02

Specification

Technical definitions for the data structures and encoding rules that constitute the underlying fabric of the Urma protocol.

1. Claim Naming

Every atomic piece of verifiable data within the protocol is identified by a deterministic claim string. The naming convention relies on a consistent prefix followed by a cryptographically secure hash.

u-{source_claim_id_hex}

The u- prefix designates the resource as a native Urma entity, distinct from raw IPFS CID hashes or standard domain name pointers. The payload must exactly equal 40 hexadecimal characters.

2. Data Structures

UrmaClaim

Primary wrapper for verifiable storage claims.

Field	Type	Description
version	uint8	Protocol version (currently 0).
location	string	Storage backend identifier (e.g. "sia").
sourceClaimId	string (hex)	40-char lowercase hex of the 20-byte source ClaimID.
dataKey	byte[32]	AES-256 encryption key for file content.
locationData	object	Backend-specific retrieval data. Schema depends on location.

ManifestPage

Paged chain structure for off-chain manifest data.

Field	Type	Description
data	json.RawMessage	Backend-specific manifest payload for this page. Opaque to core.
next	json.RawMessage	Backend-specific pointer to next page. Omitted on last page.

infoNote

Backend-specific manifest types (blob entries, slab slices, etc.) are defined by each backend, not by core. See the Sia backend for a concrete example.

3. Envelope & Signing

Claim values are wrapped in an envelope with a version byte. Unsigned envelopes (0x00) contain just the JSON payload. Signed envelopes (0x01) include a channel ClaimID and ECDSA signature.

Unsigned

[0x00] [UrmaClaim JSON bytes]

Signed

[0x01] [20-byte channel ClaimID] [64-byte ECDSA signature] [UrmaClaim JSON]

warningWarning

Invalid signatures cause immediate rejection by clients. The signature digest includes the transaction input hash, channel ClaimID, and JSON payload: useEncodeSignedEnvelope to ensure correct computation.

4. Constants

Field	Type	Description
ProtocolVersion	uint8	Current protocol version (0).
MaxClaimScriptSize	int	Maximum on-chain claim script size in bytes (8192).
SourceClaimIDLen	int	Length of a LBRY ClaimID in bytes (20).
EnvelopeUnsigned	byte	Envelope version byte for unsigned claims (0x00).
EnvelopeSigned	byte	Envelope version byte for signed claims (0x01).
EnvelopeSignedOverhead	int	Signed envelope overhead: 1 + 20 + 64 = 85 bytes.
ClaimScriptOverhead	int	Fixed script overhead: 46 bytes.