derec-library 0.0.1-alpha.8

// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2026 DeRec Alliance. All rights reserved.

//! # Cross-layer shared types
//!
//! Types used by both the primitives layer and the protocol layer. Anything
//! that's "post-pairing" or orchestrator-specific lives under
//! [`crate::protocol::types`] instead.
//!
//! ## Channel identifiers
//!
//! A [`ChannelId`] uniquely identifies the secure communication channel between
//! an Owner and a Helper for a given pairing instance.
//!
//! The identifier is derived deterministically during the pairing process from
//! the initial `ContactMessage`. Because both parties compute it from the same
//! contact data, the resulting identifier is **symmetric** — both the Owner and
//! the Helper obtain the same value without additional coordination.

/// Identifier of the secure communication channel between an Owner and a Helper.
///
/// A `ChannelId` is established during the pairing flow and uniquely identifies
/// the communication channel associated with a specific `(Owner, Helper, SecretId)`
/// relationship.
///
/// In the DeRec protocol, the `ChannelId` is deterministically derived from the
/// hash of the initial `ContactMessage`. Because both parties compute it from the
/// same contact data, the resulting identifier is **symmetric**, meaning that the
/// Owner and the Helper independently derive the same `ChannelId`.
///
/// This identifier is used internally by the library to associate protocol state
/// and messages with the correct peer.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
#[cfg_attr(
    any(feature = "serde", target_arch = "wasm32"),
    derive(serde::Serialize, serde::Deserialize),
    serde(transparent)
)]
pub struct ChannelId(pub u64);

impl From<u64> for ChannelId {
    fn from(value: u64) -> Self {
        ChannelId(value)
    }
}

impl From<ChannelId> for u64 {
    fn from(value: ChannelId) -> Self {
        value.0
    }
}

impl PartialEq<u64> for ChannelId {
    fn eq(&self, other: &u64) -> bool {
        self.0 == *other
    }
}

/// 32-byte symmetric key shared between an Owner and a Helper after pairing.
///
/// A `SharedKey` is established during the pairing flow and used to encrypt
/// and authenticate all subsequent protocol messages on the associated channel.
pub type SharedKey = [u8; 32];