payload library

Classes

DeviceBinding: DeviceBinding
KeyCustody: How a device custodies its private key material — maintainer policy input, mirroring attestation. See docs/design-notes/mobile-key-custody-profile.md.
Payload: Public discovery surface that wraps the maintainer's existing two-phase enrolment (provision-integration → acl/swap-key). A new Companion or Service hands the maintainer its long-term VTA-derived key, its consumer kind, display name, and an optional device attestation; the maintainer creates the DeviceBinding and returns it. Phase 1 (provision-integration) is assumed to have already happened — this task is the post-bootstrap claim step.
Response: Device Register — response payload

Capability: Fine-grained capability flag scoped to the device's allowed contexts. See SPEC.md for the full semantics of each. Capability values are additive: a consumer MUST ignore a value it does not recognise rather than reject the binding, and MUST NOT treat an unrecognised value as conferring anything.
KeyCustodyTier: hardware: the key is non-exportable in the secure keystore (iOS Secure Enclave / Android StrongBox) and every signing / key-agreement operation runs in-chip — achievable only with P-256. software: the key is held in app memory during use, stored hardware-wrapped at rest. Maintainers MAY apply stricter policy (shorter sessions, more frequent step-up) to software-tier devices.

payloadSchemaJson → const String: This specification's payload schema, as JSON text.
responsePayloadSchemaJson → const String: As payloadSchemaJson, for the success-response variant.
responseSpec → const SpecPolicy: The SPEC §7.2 policy for the success-response variant.
responseTypeUri → const String: The success-response form of typeUri (SPEC §4.4.1).
spec → const SpecPolicy: The SPEC §7.2 policy for the request variant, taken from this specification's front matter.
typeUri → const String: The Trust Task type URI this library's Payload is carried under.

ConsumerKind = Object?: Discriminator: is this consumer a user-driven Companion or a headless Service?
DeviceAttestation = Object?: Producer-supplied attestation at registration time, verifiable by the maintainer against the platform's attestation infrastructure. Tagged union over the discriminator kind.
Ext = Map<String, dynamic>: Vendor-namespaced extension object per SPEC.md §4.5.1. Each immediate key MUST be a reverse-DNS namespace; structure under each namespace is opaque to the framework.