ASF_01_sys_sw_arch/draft- to be removed SW/features/F-SEC_Security_Safety.md

Feature Specification: Security & Safety

Feature ID: F-SEC (F-SEC-001 to F-SEC-004)

Document Type: Feature Specification
Version: 1.0
Date: 2025-01-19
Feature Category: Security & Safety

1. Feature Overview

1.1 Feature Purpose

The Security & Safety feature provides comprehensive security enforcement and safety mechanisms for the ASF Sensor Hub. This feature ensures that only trusted firmware executes, sensitive data is protected at rest and in transit, and all communications maintain confidentiality and integrity through cryptographic mechanisms.

1.2 Feature Scope

In Scope:

• Hardware-enforced secure boot with cryptographic verification
• Flash encryption for sensitive data protection at rest
• Mutual TLS (mTLS) for secure communication channels
• Security violation detection and response mechanisms
• Device identity management and authentication

Out of Scope:

• Cloud server security policies and infrastructure
• User identity management and access control systems
• Physical tamper detection hardware (future enhancement)
• Cryptographic key generation and signing infrastructure

2. Sub-Features

2.1 F-SEC-001: Secure Boot

Description: Hardware-enforced secure boot implementation using Secure Boot V2 to ensure only authenticated and authorized firmware images execute on the Sensor Hub.

Secure Boot Configuration:

typedef struct {
    secure_boot_version_t version;    // Secure Boot V2
    signature_algorithm_t algorithm;  // RSA-3072 or ECDSA-P256
    uint8_t root_key_hash[32];       // Root-of-trust key hash (eFuse)
    bool anti_rollback_enabled;      // eFuse-based anti-rollback
    uint32_t security_version;       // Current security version
    boot_verification_mode_t mode;   // Hardware-enforced verification
} secure_boot_config_t;

typedef enum {
    SECURE_BOOT_V2 = 2               // Only supported version
} secure_boot_version_t;

typedef enum {
    SIG_ALG_RSA_3072 = 0,           // RSA-3072 signature
    SIG_ALG_ECDSA_P256 = 1          // ECDSA-P256 signature
} signature_algorithm_t;

typedef enum {
    BOOT_MODE_DEVELOPMENT = 0,       // Development mode (key revocable)
    BOOT_MODE_PRODUCTION = 1         // Production mode (key permanent)
} boot_verification_mode_t;

Boot Verification Flow:

sequenceDiagram
    participant PWR as Power On
    participant ROM as ROM Bootloader
    participant SB as Secure Boot V2
    participant EFUSE as eFuse Storage
    participant APP as Application
    participant DIAG as Diagnostics
    
    PWR->>ROM: System Reset/Power On
    ROM->>SB: Load Firmware Image
    SB->>EFUSE: readRootKeyHash()
    EFUSE-->>SB: root_key_hash
    
    SB->>SB: verifyFirmwareSignature(root_key_hash)
    
    alt Signature Valid
        SB->>SB: checkAntiRollback()
        alt Version Valid
            SB->>APP: jumpToApplication()
            APP->>DIAG: logBootEvent(SECURE_BOOT_SUCCESS)
        else Version Invalid
            SB->>SB: enterBootFailureState()
            SB->>DIAG: logBootEvent(ANTI_ROLLBACK_VIOLATION)
        end
    else Signature Invalid
        SB->>SB: enterBootFailureState()
        SB->>DIAG: logBootEvent(SECURE_BOOT_FAILURE)
    end

Root-of-Trust Management:

• Key Storage: Root public key hash stored in eFuse (one-time programmable)
• Key Revocation: Not supported in production mode (permanent key)
• Anti-Rollback: eFuse-based security version enforcement
• Verification: Every boot cycle (cold and warm boots)

Boot Failure Handling:

• BOOT_FAILURE State: System enters safe state, no application execution
• Diagnostic Logging: Boot failure events logged to NVS (if accessible)
• Recovery: Manual intervention required (re-flashing with valid firmware)

2.2 F-SEC-002: Secure Flash Storage

Description: Comprehensive flash encryption implementation using AES-256 to protect sensitive data stored in internal flash and external storage devices.

Flash Encryption Configuration:

typedef struct {
    encryption_algorithm_t algorithm; // AES-256
    encryption_mode_t mode;          // Release mode (recommended)
    uint8_t encryption_key[32];      // Hardware-derived key (eFuse)
    bool transparent_decryption;     // Automatic decryption on read
    flash_encryption_scope_t scope;  // Encrypted regions
} flash_encryption_config_t;

typedef enum {
    ENCRYPT_AES_256 = 0             // AES-256 encryption
} encryption_algorithm_t;

typedef enum {
    ENCRYPT_MODE_DEVELOPMENT = 0,    // Development mode (key readable)
    ENCRYPT_MODE_RELEASE = 1         // Release mode (key protected)
} encryption_mode_t;

typedef struct {
    bool firmware_encrypted;         // Application partitions
    bool nvs_encrypted;             // NVS partition
    bool machine_constants_encrypted; // MC data
    bool calibration_encrypted;     // Calibration data
    bool diagnostics_encrypted;     // Diagnostic logs
} flash_encryption_scope_t;

Encrypted Data Categories:

Data Type	Storage Location	Encryption Method	Access Control
Firmware Images	Flash partitions	Hardware AES-256	Transparent
Machine Constants	NVS partition	Hardware AES-256	Component-mediated
Calibration Data	NVS partition	Hardware AES-256	Component-mediated
Cryptographic Keys	eFuse/Secure NVS	Hardware AES-256	Restricted access
Diagnostic Logs	NVS partition	Hardware AES-256	Component-mediated
SD Card Data	External storage	Software AES-256	Optional encryption

External Storage Encryption:

typedef struct {
    bool sd_encryption_enabled;      // SD card encryption flag
    uint8_t sd_encryption_key[32];   // SD-specific encryption key
    encryption_algorithm_t algorithm; // AES-256 for SD card
    file_encryption_policy_t policy; // Per-file encryption policy
} external_storage_encryption_t;

typedef enum {
    FILE_ENCRYPT_NONE = 0,          // No encryption
    FILE_ENCRYPT_SENSITIVE = 1,     // Encrypt sensitive files only
    FILE_ENCRYPT_ALL = 2            // Encrypt all files
} file_encryption_policy_t;

Encryption Flow:

sequenceDiagram
    participant APP as Application
    participant PERSIST as Persistence
    participant ENCRYPT as Encryption Engine
    participant NVS as NVS Storage
    participant SD as SD Card
    
    Note over APP,SD: Secure Data Storage Flow
    
    APP->>PERSIST: storeSensitiveData(data, type)
    PERSIST->>PERSIST: classifyDataSensitivity(type)
    
    alt Critical Data (NVS)
        PERSIST->>ENCRYPT: encryptData(data, NVS_KEY)
        ENCRYPT-->>PERSIST: encrypted_data
        PERSIST->>NVS: writeEncrypted(encrypted_data)
        NVS-->>PERSIST: writeComplete()
    else Regular Data (SD Card)
        alt SD Encryption Enabled
            PERSIST->>ENCRYPT: encryptData(data, SD_KEY)
            ENCRYPT-->>PERSIST: encrypted_data
            PERSIST->>SD: writeEncrypted(encrypted_data)
        else SD Encryption Disabled
            PERSIST->>SD: writePlaintext(data)
        end
    end
    
    PERSIST-->>APP: storageComplete()

2.3 F-SEC-003: Encrypted Communication

Description: Mutual TLS (mTLS) implementation for secure communication with Main Hub and peer devices, ensuring confidentiality, integrity, and authenticity of all transmitted data.

Device Identity and Authentication:

typedef struct {
    uint8_t device_certificate[2048]; // X.509 device certificate (max 2KB)
    uint8_t private_key[256];        // Device private key (RSA-2048/ECDSA-P256)
    uint8_t ca_certificate[2048];    // Certificate Authority certificate
    char device_id[64];              // Unique device identifier
    uint64_t certificate_expiry;     // Certificate expiration timestamp
    bool certificate_valid;          // Certificate validation status
} device_identity_t;

typedef struct {
    tls_version_t version;           // TLS 1.2 minimum
    cipher_suite_t cipher_suite;     // Supported cipher suites
    bool mutual_auth_required;       // mTLS enforcement
    uint32_t session_timeout;        // TLS session timeout
    bool session_resumption;         // Session resumption support
} tls_config_t;

typedef enum {
    TLS_VERSION_1_2 = 0x0303,       // TLS 1.2 (minimum required)
    TLS_VERSION_1_3 = 0x0304        // TLS 1.3 (preferred)
} tls_version_t;

Supported Cipher Suites:

Cipher Suite	Key Exchange	Encryption	MAC	Recommended
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384	ECDHE-RSA	AES-256-GCM	SHA384	Yes
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384	ECDHE-ECDSA	AES-256-GCM	SHA384	Yes
TLS_RSA_WITH_AES_256_GCM_SHA384	RSA	AES-256-GCM	SHA384	Fallback

mTLS Handshake Flow:

sequenceDiagram
    participant SH as Sensor Hub
    participant MH as Main Hub
    participant CA as Certificate Authority
    
    Note over SH,CA: Mutual TLS Handshake
    
    SH->>MH: ClientHello + SupportedCipherSuites
    MH->>SH: ServerHello + SelectedCipherSuite
    MH->>SH: ServerCertificate
    MH->>SH: CertificateRequest
    MH->>SH: ServerHelloDone
    
    SH->>SH: validateServerCertificate()
    SH->>CA: verifyCertificateChain(server_cert)
    CA-->>SH: validationResult(VALID)
    
    SH->>MH: ClientCertificate
    SH->>MH: ClientKeyExchange
    SH->>MH: CertificateVerify
    SH->>MH: ChangeCipherSpec
    SH->>MH: Finished
    
    MH->>MH: validateClientCertificate()
    MH->>CA: verifyCertificateChain(client_cert)
    CA-->>MH: validationResult(VALID)
    
    MH->>SH: ChangeCipherSpec
    MH->>SH: Finished
    
    Note over SH,MH: Secure Channel Established
    
    SH<->>MH: EncryptedApplicationData

Certificate Management:

• Device Certificate: Unique X.509 certificate per device (max 2KB)
• Private Key: RSA-2048 or ECDSA-P256 stored securely in eFuse/NVS
• Certificate Chain: Root CA and intermediate certificates
• Certificate Rotation: Managed on broker/server side
• Revocation: Certificate Revocation Lists (CRL) or broker-side denylists

Key Lifecycle Management:

Phase	Mechanism	Responsibility
Manufacturing	Device certificate and private key injection	Manufacturing process
Provisioning	Certificate validation and registration	Onboarding system
Operation	TLS session key generation and management	Runtime TLS stack
Rotation	Certificate renewal and update	Server-side management
Revocation	Certificate invalidation and replacement	Certificate Authority

2.4 F-SEC-004: Security Violation Handling

Description: Comprehensive security violation detection, classification, and response system to handle security threats and maintain system integrity.

Security Violation Types:

typedef enum {
    SEC_VIOLATION_BOOT_FAILURE = 0x1001,      // Secure boot verification failure
    SEC_VIOLATION_AUTH_FAILURE = 0x1002,      // Authentication failure
    SEC_VIOLATION_CERT_INVALID = 0x1003,      // Certificate validation failure
    SEC_VIOLATION_MESSAGE_TAMPER = 0x1004,    // Message integrity violation
    SEC_VIOLATION_UNAUTHORIZED_ACCESS = 0x1005, // Unauthorized access attempt
    SEC_VIOLATION_ROLLBACK_ATTEMPT = 0x1006,  // Anti-rollback violation
    SEC_VIOLATION_KEY_COMPROMISE = 0x1007,    // Cryptographic key compromise
    SEC_VIOLATION_REPLAY_ATTACK = 0x1008      // Message replay attack
} security_violation_type_t;

typedef struct {
    security_violation_type_t type;   // Violation type
    diagnostic_severity_t severity;   // FATAL, ERROR, WARNING
    uint64_t timestamp;              // Violation timestamp
    char source_component[32];       // Component that detected violation
    char description[128];           // Human-readable description
    uint8_t context_data[64];        // Violation-specific context
    uint32_t occurrence_count;       // Number of occurrences
    bool escalation_triggered;       // Escalation flag
} security_violation_event_t;

Violation Response Matrix:

Violation Type	Severity	Immediate Response	Escalation Action
Boot Failure	FATAL	Enter BOOT_FAILURE state	System halt, manual recovery
Auth Failure	ERROR	Reject connection, log event	Escalate to FATAL after 3 failures
Cert Invalid	ERROR	Reject connection, log event	Escalate to FATAL if persistent
Message Tamper	WARNING	Discard message, log event	Escalate to ERROR if repeated
Unauthorized Access	FATAL	Deny access, log event	System lockdown
Rollback Attempt	FATAL	Prevent rollback, log event	System halt
Key Compromise	FATAL	Revoke keys, log event	System lockdown
Replay Attack	WARNING	Discard message, log event	Escalate to ERROR if persistent

Security Event Flow:

sequenceDiagram
    participant COMP as Security Component
    participant SEC as Security Manager
    participant DIAG as Diagnostics
    participant STM as State Manager
    participant LOG as Security Logger
    
    Note over COMP,LOG: Security Violation Detection and Response
    
    COMP->>SEC: reportSecurityViolation(type, context)
    SEC->>SEC: classifyViolation(type)
    SEC->>SEC: determineResponse(type, severity)
    
    alt Severity == FATAL
        SEC->>STM: triggerStateTransition(FAULT)
        SEC->>LOG: logSecurityEvent(FATAL, details)
        SEC->>DIAG: reportDiagnosticEvent(FATAL, violation)
    else Severity == ERROR
        SEC->>SEC: checkEscalationCriteria()
        alt Escalation Required
            SEC->>STM: triggerStateTransition(WARNING)
        end
        SEC->>LOG: logSecurityEvent(ERROR, details)
        SEC->>DIAG: reportDiagnosticEvent(ERROR, violation)
    else Severity == WARNING
        SEC->>LOG: logSecurityEvent(WARNING, details)
        SEC->>DIAG: reportDiagnosticEvent(WARNING, violation)
    end
    
    SEC->>SEC: updateViolationStatistics()
    SEC->>SEC: checkPatterns()

Escalation Criteria:

• Authentication Failures: 3 consecutive failures within 5 minutes
• Message Tampering: 5 tampered messages within 1 minute
• Certificate Violations: Persistent certificate validation failures
• Pattern Detection: Coordinated attack patterns across multiple violation types

3. Requirements Coverage

3.1 System Requirements (SR-XXX)

Feature	System Requirements	Description
F-SEC-001	SR-SEC-001, SR-SEC-002, SR-SEC-003, SR-SEC-004	Secure boot verification and root-of-trust protection
F-SEC-002	SR-SEC-005, SR-SEC-006, SR-SEC-007, SR-SEC-008	Flash encryption and secure storage
F-SEC-003	SR-SEC-009, SR-SEC-010, SR-SEC-011, SR-SEC-012	Encrypted communication and mTLS
F-SEC-004	SR-SEC-013, SR-SEC-014, SR-SEC-015	Security violation handling and response

3.2 Software Requirements (SWR-XXX)

Feature	Software Requirements	Implementation Details
F-SEC-001	SWR-SEC-001, SWR-SEC-002, SWR-SEC-003	Boot verification, signature validation, anti-rollback
F-SEC-002	SWR-SEC-004, SWR-SEC-005, SWR-SEC-006	AES-256 encryption, key management, storage protection
F-SEC-003	SWR-SEC-007, SWR-SEC-008, SWR-SEC-009	mTLS implementation, certificate management, session security
F-SEC-004	SWR-SEC-010, SWR-SEC-011, SWR-SEC-012	Violation detection, response coordination, escalation logic

4. Component Implementation Mapping

4.1 Primary Components

Component	Responsibility	Location
Security Manager	Security policy enforcement, violation handling	application_layer/security/
Secure Boot	Boot-time firmware verification	bootloader/secure_boot/
Encryption Engine	Cryptographic operations, key management	application_layer/security/crypto/
Certificate Manager	Certificate validation, lifecycle management	application_layer/security/cert_mgr/

4.2 Supporting Components

Component	Support Role	Interface
Network Stack	TLS/DTLS transport layer	drivers/network_stack/
NVM Driver	Secure storage access	drivers/nvm/
Diagnostics	Security event logging	application_layer/diag_task/
State Manager	Security-triggered state transitions	application_layer/business_stack/STM/

4.3 Component Interaction Diagram

graph TB
    subgraph "Security & Safety Feature"
        SEC[Security Manager]
        BOOT[Secure Boot]
        CRYPTO[Encryption Engine]
        CERT[Certificate Manager]
    end
    
    subgraph "System Components"
        STM[State Manager]
        DIAG[Diagnostics]
        NET[Network Stack]
        NVM[NVM Driver]
    end
    
    subgraph "Hardware Security"
        EFUSE[eFuse Storage]
        HWCRYPTO[Hardware Crypto]
        FLASH[Flash Memory]
    end
    
    subgraph "External Interfaces"
        MH[Main Hub]
        CA[Certificate Authority]
    end
    
    BOOT --> EFUSE
    BOOT --> HWCRYPTO
    BOOT --> SEC
    
    SEC <--> STM
    SEC <--> DIAG
    SEC --> CRYPTO
    SEC --> CERT
    
    CRYPTO --> HWCRYPTO
    CRYPTO --> NVM
    
    CERT --> NET
    CERT --> CA
    
    NET <-->|mTLS| MH
    
    SEC -.->|Security Events| DIAG
    STM -.->|State Changes| SEC

4.4 Security Enforcement Flow

sequenceDiagram
    participant BOOT as Secure Boot
    participant SEC as Security Manager
    participant CRYPTO as Encryption Engine
    participant CERT as Certificate Manager
    participant NET as Network Stack
    participant MH as Main Hub
    
    Note over BOOT,MH: Security Enforcement Flow
    
    BOOT->>BOOT: verifyFirmwareSignature()
    BOOT->>SEC: secureBootComplete(SUCCESS)
    SEC->>SEC: initializeSecurityPolicies()
    
    SEC->>CRYPTO: initializeEncryption()
    CRYPTO->>CRYPTO: loadEncryptionKeys()
    
    SEC->>CERT: initializeCertificates()
    CERT->>CERT: validateDeviceCertificate()
    
    NET->>CERT: establishTLSConnection(main_hub)
    CERT->>CERT: performMutualAuthentication()
    CERT-->>NET: tlsConnectionEstablished()
    
    NET<->>MH: secureDataExchange()
    
    alt Security Violation Detected
        SEC->>SEC: handleSecurityViolation(type)
        SEC->>DIAG: logSecurityEvent(violation)
        SEC->>STM: triggerSecurityResponse(action)
    end

5. Feature Behavior

5.1 Normal Operation Flow

1. Boot-Time Security:

   • Secure Boot V2 verifies firmware signature using root-of-trust
   • Anti-rollback mechanism prevents firmware downgrade attacks
   • Flash encryption automatically decrypts application code
   • Security Manager initializes and loads security policies

2. Runtime Security:

   • All communication channels use mTLS with mutual authentication
   • Sensitive data encrypted before storage using AES-256
   • Certificate validation performed for all external connections
   • Security violations monitored and logged continuously

3. Communication Security:

   • Device certificate presented during TLS handshake
   • Server certificate validated against trusted CA chain
   • Encrypted data exchange using negotiated cipher suite
   • Session keys rotated according to security policy

4. Violation Response:

   • Security violations detected and classified by severity
   • Immediate response actions taken based on violation type
   • Escalation logic applied for repeated or coordinated attacks
   • Security events logged for audit and analysis

5.2 Error Handling

Error Condition	Detection Method	Response Action
Boot Verification Failure	Signature validation failure	Enter BOOT_FAILURE state, halt system
Certificate Validation Failure	X.509 validation error	Reject connection, log security event
Encryption Key Failure	Key derivation/access error	Enter FAULT state, disable encryption
TLS Handshake Failure	Protocol negotiation failure	Retry with fallback, log failure
Message Integrity Failure	MAC/signature verification failure	Discard message, log tampering event
Anti-Rollback Violation	Version check failure	Prevent boot, log violation

5.3 State-Dependent Behavior

System State	Feature Behavior
INIT	Initialize security components, load certificates and keys
RUNNING	Full security enforcement, continuous violation monitoring
WARNING	Enhanced security monitoring, stricter validation
FAULT	Critical security functions only, preserve security logs
OTA_UPDATE	Secure OTA validation, maintain security during update
TEARDOWN	Secure data flush, maintain encryption during shutdown
SERVICE	Limited security access for diagnostics
BOOT_FAILURE	Security violation state, no application execution

6. Feature Constraints

6.1 Timing Constraints

• Boot Verification: Maximum 5 seconds for secure boot completion
• TLS Handshake: Maximum 10 seconds for mTLS establishment
• Certificate Validation: Maximum 2 seconds per certificate
• Violation Response: Maximum 100ms for immediate response actions

6.2 Resource Constraints

• Certificate Storage: Maximum 2KB per certificate (device, CA)
• Key Storage: Secure storage in eFuse or encrypted NVS
• Memory Usage: Maximum 64KB for security buffers and state
• CPU Usage: Maximum 10% for cryptographic operations

6.3 Security Constraints

• Root-of-Trust: eFuse-based, one-time programmable
• Key Protection: Hardware-protected keys, no plaintext exposure
• Certificate Validation: Full chain validation required
• Encryption Strength: AES-256 minimum for all encryption

7. Interface Specifications

7.1 Security Manager Public API

// Security initialization and control
bool secMgr_initialize(void);
bool secMgr_isSecurityEnabled(void);
security_status_t secMgr_getSecurityStatus(void);

// Violation handling
bool secMgr_reportViolation(security_violation_type_t type, 
                           const char* source, const uint8_t* context);
bool secMgr_getViolationHistory(security_violation_event_t* events, size_t* count);
bool secMgr_clearViolationHistory(void);

// Security policy management
bool secMgr_setSecurityPolicy(const security_policy_t* policy);
bool secMgr_getSecurityPolicy(security_policy_t* policy);
bool secMgr_enforceSecurityPolicy(void);

7.2 Encryption Engine API

// Encryption operations
bool crypto_encrypt(const uint8_t* plaintext, size_t plaintext_len,
                   const uint8_t* key, uint8_t* ciphertext, size_t* ciphertext_len);
bool crypto_decrypt(const uint8_t* ciphertext, size_t ciphertext_len,
                   const uint8_t* key, uint8_t* plaintext, size_t* plaintext_len);

// Hash operations
bool crypto_sha256(const uint8_t* data, size_t data_len, uint8_t* hash);
bool crypto_hmac_sha256(const uint8_t* data, size_t data_len,
                       const uint8_t* key, size_t key_len, uint8_t* hmac);

// Key management
bool crypto_generateKey(key_type_t type, uint8_t* key, size_t key_len);
bool crypto_deriveKey(const uint8_t* master_key, const char* context,
                     uint8_t* derived_key, size_t key_len);

7.3 Certificate Manager API

// Certificate operations
bool certMgr_loadDeviceCertificate(const uint8_t* cert_data, size_t cert_len);
bool certMgr_validateCertificate(const uint8_t* cert_data, size_t cert_len);
bool certMgr_getCertificateInfo(certificate_info_t* info);

// TLS integration
bool certMgr_setupTLSContext(tls_context_t* ctx);
bool certMgr_validatePeerCertificate(const uint8_t* peer_cert, size_t cert_len);
bool certMgr_getTLSCredentials(tls_credentials_t* credentials);

8. Testing and Validation

8.1 Unit Testing

• Secure Boot: Firmware signature validation with valid/invalid signatures
• Encryption: AES-256 encryption/decryption with known test vectors
• Certificate Validation: X.509 certificate parsing and validation
• Violation Handling: All violation types and response actions

8.2 Integration Testing

• End-to-End Security: Complete security flow from boot to communication
• mTLS Integration: Full TLS handshake with certificate validation
• State Integration: Security behavior across all system states
• Cross-Component Security: Security enforcement across all components

8.3 System Testing

• Security Penetration Testing: Simulated attacks and vulnerability assessment
• Performance Testing: Cryptographic operations under load
• Fault Injection: Security behavior under hardware/software faults
• Long-Duration Testing: Security stability over extended operation

8.4 Acceptance Criteria

• Secure boot prevents execution of unsigned firmware
• All sensitive data encrypted at rest and in transit
• mTLS successfully established with valid certificates
• Security violations properly detected and responded to
• No security vulnerabilities identified in penetration testing
• Performance impact of security features within acceptable limits
• Complete audit trail of all security events

9. Dependencies

9.1 Internal Dependencies

• State Manager: Security-triggered state transitions
• Diagnostics: Security event logging and audit trail
• Network Stack: TLS/DTLS transport implementation
• NVM Driver: Secure storage for keys and certificates

9.2 External Dependencies

• ESP-IDF Security Features: Secure Boot V2, Flash Encryption, eFuse
• Hardware Security Module: Hardware-accelerated cryptography
• Certificate Authority: Certificate validation and management
• Cryptographic Libraries: mbedTLS or equivalent for TLS implementation

10. Future Enhancements

10.1 Planned Improvements

• Hardware Security Module: Dedicated HSM for key management
• Physical Tamper Detection: Hardware-based tamper detection
• Advanced Threat Detection: Machine learning-based anomaly detection
• Quantum-Resistant Cryptography: Post-quantum cryptographic algorithms

10.2 Scalability Considerations

• Fleet Security Management: Centralized security policy management
• Certificate Automation: Automated certificate lifecycle management
• Security Analytics: Advanced security event correlation and analysis
• Zero-Trust Architecture: Comprehensive zero-trust security model

---

Document Status: Final for Implementation Phase
Component Dependencies: Verified against architecture
Requirements Traceability: Complete (SR-SEC, SWR-SEC)
Next Review: After component implementation