Crypto Utils Component

ASF Sensor Hub (Sub-Hub) Embedded System

Component ID: C-CRYPTO-001
Version: 1.0
Date: 2025-02-01
Location: application_layer/utils/crypto_utils/
Platform: ESP32-S3, ESP-IDF v5.4

1. Component Overview

The Crypto Utils component provides cryptographic utility functions including hash computation, encryption/decryption, digital signatures, secure random number generation, and key derivation. This component supports Security Manager and other security-critical components.

Primary Purpose: Provide cryptographic primitives for system security.

2. Responsibilities

2.1 In-Scope

Hash function computation (SHA-256, SHA-512)
Symmetric encryption/decryption (AES-128, AES-256)
Digital signature verification (RSA, ECDSA)
Secure random number generation
Key derivation functions (PBKDF2, HKDF)
Message authentication codes (HMAC)

2.2 Out-of-Scope

Key storage (handled by Security Manager)
Certificate management (handled by Security Manager)
Secure boot (handled by ESP-IDF)

3. Provided Interfaces

3.1 Hash Functions

/**
 * @brief Compute SHA-256 hash
 * @param data Input data
 * @param data_len Data length
 * @param hash Output hash (32 bytes)
 * @return true on success
 */
bool crypto_hash_sha256(const uint8_t* data, size_t data_len, uint8_t* hash);

/**
 * @brief Compute SHA-512 hash
 * @param data Input data
 * @param data_len Data length
 * @param hash Output hash (64 bytes)
 * @return true on success
 */
bool crypto_hash_sha512(const uint8_t* data, size_t data_len, uint8_t* hash);

3.2 Encryption Functions

/**
 * @brief Encrypt data using AES-256
 * @param plaintext Input plaintext
 * @param plaintext_len Plaintext length
 * @param key Encryption key (32 bytes)
 * @param iv Initialization vector (16 bytes)
 * @param ciphertext Output ciphertext
 * @return true on success
 */
bool crypto_encrypt_aes256(const uint8_t* plaintext, size_t plaintext_len,
                           const uint8_t* key, const uint8_t* iv,
                           uint8_t* ciphertext, size_t* ciphertext_len);

3.3 Random Number Generation

/**
 * @brief Generate secure random bytes
 * @param buffer Output buffer
 * @param length Number of bytes to generate
 * @return true on success
 */
bool crypto_random_bytes(uint8_t* buffer, size_t length);

4. ESP-IDF Integration

4.1 ESP-IDF Services Used

mbedtls/sha256.h - SHA-256 computation
mbedtls/aes.h - AES encryption
mbedtls/rsa.h - RSA operations
esp_random.h - Secure random number generation
Hardware acceleration (ESP32-S3 crypto peripherals)

4.2 Hardware Acceleration

AES encryption/decryption (hardware-accelerated)
SHA computation (hardware-accelerated)
Random number generation (hardware RNG)

5. Traceability

11.1 Software Requirements

SWR-SEC-022: Secure random number generation
SWR-SEC-023: Key derivation functions
SWR-OTA-007: Firmware integrity validation (SHA-256)

Document Status: Complete
Next Review: Before implementation

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