Quantum Security Architecture

Security Architecture Overview

The Zi Stack implements a multi-layered security architecture combining classical zero-trust principles with quantum-native protections. Our topological quantum computation approach provides inherent fault tolerance through non-Abelian anyons, while post-quantum cryptographic primitives ensure long-term data protection against quantum adversaries.

Topological Quantum Protection

We encode quantum information in topologically protected states using non-Abelian anyons. This provides inherent fault tolerance—errors require global operations to corrupt data, making local noise harmless.

module topological_braid(
    input wire [2:0] gate_voltages,
    output wire [1:0] anyon_positions
);
    // Adiabatic braiding sequence
    parameter T_braid = 100ns;  // Much less than T2*
    parameter V_min = -2.0;
    parameter V_max = 2.0;
    
    // Voltage sequences for exchanging anyons
    reg [11:0] braid_sequence [0:7];
    
    always @(posedge clock) begin
        // Apply Fibonacci representation matrices
        // F_matrix for fusion, R_matrix for braiding
        F_matrix = {{phi^-1, phi^-0.5}, {phi^-0.5, -phi^-1}};
        R_matrix = diag(e^{i*pi/5}, e^{-i*pi/5});
        
        // Braiding unitary: ρ(σ_i) = R ⊕ F·R·F⁻¹
        // Topologically protected against local perturbations
    end
endmodule

Surface Code with Twist Defects

We implement the Z₂ × Z₂ quantum double model with twist defects for logical qubit encoding, achieving error rates below the fault-tolerance threshold.

struct TopologicalMemory {
    lattice: RaussendorfLattice,
    stabilizers: Vec,
    decoder: UnionFindDecoder,
    magic_state_factory: DistillationFactory,
}

impl TopologicalMemory {
    fn correct_errors(&mut self) -> Result<(), TopologicalError> {
        // Measure stabilizers in 8μs cycle
        let syndromes = self.measure_syndromes_parallel();
        
        // MWPM decoder with O(n log n) complexity
        let correction = self.decoder.decode(
            syndromes,
            PhenomenologicalModel::new(
                p_measurement: 1e-3,
                p_qubit: 1e-3,
            )
        );
        
        // Apply corrections via lattice surgery
        self.apply_topological_correction(correction)?;
        
        // Magic state distillation for T-gates (15-to-1 protocol)
        let magic_state = self.magic_state_factory.distill(
            input_fidelity: 0.99,
            target_fidelity: 0.9999,
            protocol: BravyiHaah15To1,
        );
        
        Ok(())
    }
}

Post-Quantum Cryptography

All cryptographic primitives are quantum-resistant, protecting against both current and future quantum adversaries. We implement NIST PQC standards alongside experimental quantum signature schemes.

Quantum Key Distribution

We implement device-independent QKD using the Ekert 91 protocol with CHSH inequality verification for unconditional security.

class DeviceIndependentQKD:
    def __init__(self, photon_source, detectors):
        self.source = photon_source  # Entangled photon pair source
        self.detectors = detectors   # Single-photon avalanche diodes
        self.chsh_threshold = 2.82   # 2√2 - ε for security
        
    def generate_key(self, length: int) -> bytes:
        key_bits = []
        violation_history = []
        
        for i in range(length * 10):  # Oversample for sifting
            # Generate maximally entangled Bell pair |Φ+⟩
            photon_pair = self.source.generate_entangled()
            
            # Random basis selection (24 settings for loophole-free)
            basis_A = random.choice(range(24))
            basis_B = random.choice(range(24))
            
            # Spacelike-separated measurements
            outcome_A = self.detectors.alice.measure(basis_A)
            outcome_B = self.detectors.bob.measure(basis_B)
            
            # CHSH value calculation for Bell test bases
            if self.is_bell_test_basis(basis_A, basis_B):
                S = self.calculate_chsh(outcome_A, outcome_B)
                violation_history.append(S)
                
                # Abort if Bell violation insufficient (eavesdropping)
                if len(violation_history) > 100:
                    if np.mean(violation_history[-100:]) < self.chsh_threshold:
                        raise SecurityBreach("CHSH violation below threshold - eavesdropping detected")
            
            # Sifting: keep matching bases for key
            if basis_A == basis_B and outcome_A == outcome_B:
                key_bits.append(outcome_A)
                
        # Privacy amplification via 2-universal hashing
        # Final key rate: r = 1 - h(Q) - leak_EC
        return self.privacy_amplification(key_bits, length)

Quantum Repeater Network

Quantum-Secure Blockchain

Policy management and audit trails are stored on a quantum-resistant blockchain using lattice-based signatures and quantum Byzantine agreement.

Hardware Security Module

Cryptographic operations execute within FIPS 140-3 Level 3 certified hardware security modules integrated with our cryogenic quantum systems.

HSM Integration

Hardware Attestation Protocol

struct HardwareAttestation {
    tpm: TrustedPlatformModule,
    endorsement_key: EK,
    attestation_key: AK,
    pcr_values: [u8; 24],
}

impl HardwareAttestation {
    async fn remote_attestation(&self, verifier: &Verifier) -> Result {
        // Step 1: Generate fresh nonce from verifier
        let nonce = verifier.get_challenge().await?;
        
        // Step 2: Collect platform measurements
        let quote = self.tpm.quote(
            pcr_selection: [0, 1, 2, 7, 14],  // Boot chain + kernel
            nonce: nonce,
            signing_key: &self.attestation_key,
        )?;
        
        // Step 3: Include quantum-specific measurements
        let quantum_state = QuantumMeasurement {
            coherence_times: self.measure_t1_t2(),
            error_rates: self.run_rb_sequence(),
            calibration_hash: self.calibration_data.hash(),
        };
        
        // Step 4: Sign with HSM-protected key
        let signature = self.hsm.sign_dilithium(
            &[quote.as_bytes(), quantum_state.as_bytes()].concat()
        )?;
        
        // Step 5: Send to verifier
        verifier.verify_attestation(AttestationReport {
            quote,
            quantum_state,
            signature,
            certificate_chain: self.get_cert_chain(),
        }).await
    }
}

Compliance & Certifications

Immutable Audit Trail

class QuantumAuditTrail:
    """
    Tendermint-based immutable audit log with quantum signatures.
    """
    
    def __init__(self, validators: List[ValidatorNode]):
        self.chain = TendermintChain(validators)
        self.merkle_tree = QuantumMerkleTree()
        
    async def log_event(self, event: AuditEvent) -> AuditReceipt:
        # Sign event with post-quantum signature
        signature = self.hsm.sign_dilithium(event.serialize())
        
        # Add to quantum Merkle tree
        leaf_hash = sha3_512(event.serialize() + signature)
        merkle_proof = self.merkle_tree.insert(leaf_hash)
        
        # Submit to Tendermint consensus
        tx = Transaction(
            event=event,
            signature=signature,
            merkle_proof=merkle_proof,
            timestamp=self.quantum_clock.now(),
        )
        
        # Wait for 2/3+ validator signatures (BFT consensus)
        receipt = await self.chain.submit_and_wait(tx)
        
        return AuditReceipt(
            block_height=receipt.height,
            tx_hash=receipt.hash,
            merkle_root=self.merkle_tree.root,
            validator_signatures=receipt.signatures,
        )
        
    def verify_event(self, receipt: AuditReceipt) -> bool:
        # Verify inclusion in blockchain
        block = self.chain.get_block(receipt.block_height)
        
        # Verify Merkle proof
        return self.merkle_tree.verify_proof(
            leaf=receipt.tx_hash,
            proof=receipt.merkle_proof,
            root=block.merkle_root
        )

Risk Mitigation Strategy

Technical Risks

Security Scaling Timeline

Security Resources

• Threat model documentation and attack surface analysis
• Post-quantum cryptography migration guide
• Quantum key distribution protocol specifications
• Hardware security module integration manual
• Compliance automation playbooks (SOC2, PCI-DSS, SOX)
• Incident response procedures for quantum systems