Device identity and signed telemetry for the pamoja SDK.

Many of the deployments this SDK is built for - vaccine fridges, clinic telemetry, water and energy metering - need their data to be trustworthy, not just delivered. A reading that drives a health or billing decision has to be provably from the device that claims to have sent it, and provably unaltered on the way. This crate provides that foundation with ed25519 signatures:

• [DeviceIdentity] - a device's private key, built from a provisioned 32-byte seed, that signs the payloads the device emits.
• [PublicIdentity] - the matching public key, safe to share, that a gateway or auditor uses to verify a payload is authentic and unaltered.
• [Signature] - the 64-byte detached signature carried alongside a payload.

Signing and verifying are deterministic and need no randomness, so the crate is no_std and runs unchanged on a microcontroller that signs its own telemetry. It is the groundwork the security pillar builds on, ahead of transport-level TLS/DTLS and signed over-the-air updates.

Examples

Sign a reading on the device, then verify it as an auditor would:

use pamoja_security::DeviceIdentity;

// A device is provisioned with a 32-byte secret seed.
let device = DeviceIdentity::from_seed(&[42u8; 32]);
let public = device.public();

// It signs a reading; the signature travels with the data.
let reading = b"fridge-1: 4.8C @ 1700";
let signature = device.sign(reading);

// An auditor with the device's public identity confirms it is authentic.
assert!(public.verify(reading, &signature).is_ok());

// A tampered reading does not verify.
assert!(public.verify(b"fridge-1: 9.9C @ 1700", &signature).is_err());