---
title: "SPsec Hardware Requirements — Key Store, RNG and Timer"
canonical_url: "https://cancrypt.net/spsec/hardware/"
description: "The hardware SPsec relies on: secure key storage that cannot be read out, a true random number generator and a synchronized timer, with assurance levels."
last_updated: "2026-07-13"
---
# Hardware Requirements

SPsec is deliberately modest about hardware, but three security functions must be available to the sublayer.

### Secure Key Storage

Long-lived keys that cannot be read out, even by an attacker with physical access to the chip.

### True Random Numbers

Unpredictable entropy for nonces, salts, session establishment and counter initialization.

### Synchronized Timer

A free-running tick, shared across the group by the Sync role, that supplies a non-repeating uniqueness value.

## Secure Key Storage

The long-lived keys (Provisioning, Integrator and Seed) must be stored so that they cannot be read out, even by an attacker with physical access to the chip. A hardware security module or a security-hardened microcontroller with a trusted zone is preferred. Where on-die secure storage is limited, a single device-specific key can encrypt the rest of the key material held in ordinary non-volatile memory. Keys are addressed through an opaque selector rather than a raw pointer, and they are never read back out of the device.

## True Random Number Generator

A source of unpredictable randomness is required for nonces, salts and session establishment, and for initializing counters safely. Hardware entropy is required at higher assurance levels; a software-only generator is acceptable only at the lowest levels, and only when its seed is genuinely non-reproducible, for example a combination of analog inputs, timer jitter and stored state.

## Synchronized Timer

Grouped communication needs a uniqueness value that never repeats under one key. SPsec uses a free-running timer that ticks every 0.1 ms and is shared across the group by the Sync role. If the timer is initialized from a random value it must be at least 128 bits wide to rule out nonce reuse; preferably it reflects total runtime and continues across power cycles using cyclic non-volatile storage. The Sync role is responsible for keeping the value unique.

## Frequently Asked Questions

### What hardware does SPsec require?

Three security functions: secure key storage that cannot be read out, a true random number generator and a synchronized timer. The cryptographic algorithms themselves run in software or an accelerator.

### Is a hardware random number generator mandatory?

At higher assurance levels, yes. A software-only generator is acceptable only at the lowest levels, and only when its seed is genuinely non-reproducible.