# description
A cryptographic binding that explicitly ties a callback to the specific inbound request that triggered it. Establishes bilateral non-repudiation for the asynchronous leg of a Beckn interaction.  Use `lineage` (on `Context`) for cross-transaction causality.  Verification steps: 1. Recompute BLAKE2b-512 digest of the original request body; compare to `digest`. 2. Confirm `messageId` matches the `messageId` from the original request `Context`.

# properties.digest.description
BLAKE2b-512 hash of the parent request body, Base64-encoded with algorithm prefix. Format: `BLAKE-512={base64EncodedHash}`