Space-Grade Physics: Radiation Hardening & Hybrid Security

This chapter details the "Immortal Architecture" implemented in PQC-Boot, designed to withstand the physical extremities of deep space and the mathematical uncertainties of the post-quantum era.

1. Single Event Upsets (SEUs) and The Physics of Failure

In high-radiation environments (Low Earth Orbit, Van Allen Belts, or near Neutron Degeneration within reactors), ionizing particles can strike memory cells.

The Physics

A heavy ion striking a silicon depletion region generates electron-hole pairs. If the deposited charge $Q_{dep}$ exceeds the critical charge $Q_{crit}$ of the memory cell, a bit flip occurs (0 $\to$ 1).

$$ P(SEU) \propto \Phi \cdot \sigma_{cross} $$ Where $\Phi$ is particle flux and $\sigma_{cross}$ is the device cross-section.

The Mitigation: Software Triple Modular Redundancy (SW-TMR)

PQC-Boot does not rely on ECC RAM alone. It implements Tri-State Logic for all critical variables (Active Partition, Retry Counters).

Logic: Let state $S$ be stored as vector $\mathbf{v} = \langle v_1, v_2, v_3 \rangle$. The Read Operation $R(\mathbf{v})$ is defined as:

$$ R(\mathbf{v}) = (v_1 \land v_2) \lor (v_2 \land v_3) \lor (v_1 \land v_3) $$

Self-Healing Probability: Assuming independent bit-flip probability $p_{err} = 10^{-9}$ per cycle. The probability of a system failure $P_{sys}$ (2 simultaneous bit flips in same word) is:

$$ P_{sys} \approx 3 \cdot p_{err}^2 \approx 3 \cdot 10^{-18} $$

This transforms a "Wait and Die" system into an "Immortal" self-repairing system.

2. The Hybrid "Bet-Hedge" Model

As defined in Task 13, relying solely on new math (Lattice Cryptography) is a risk for mission-critical systems with 30-year lifespans.

The Strategy

We verify AND conditions, not OR.

$$ \text{Valid} = \text{Verify}{Falcon}(M, S{pq}) \land \text{Verify}{Ed25519}(M, S{cl}) $$

Failure Modes Analysis

Implementation: Hybrid Post-Quantum (PQH)

In Galactic Apex (V4), we implement a Hybrid KEM for session keys. We mix the outputs of Kyber-1024 and X25519 using HKDF-SHA256.

#![allow(unused)]
fn main() {
// PqcClient::complete_connection
let k_secret = kyber.decapsulate(k_sk, kyber_ct)?;
let x_secret = x_sk.diffie_hellman(&server_x_pk);

// Mix secrets via HKDF
let mut combiner = Hkdf::<Sha256>::new(None, &k_secret);
let mut final_secret = [0u8; 32];
combiner.expand(&x_secret.to_bytes(), &mut final_secret)?;

// Session is protected by both Lattice hardness and ECC
let session = RatchetSession::initialize(final_secret, ...);
}

If one is broken, the final secret remains computationally infeasible to derive. This is the V4 Galactic Apex standard.