text: #ifndef __ESP_CRYPTO_H__
  #define __ESP_CRYPTO_H__
  #include <Arduino.h>
  
  // Length in bytes of SHA256 hash
  #define SHA256_LENGTH 32
  
  void sha256_hash(const uint8_t *payload, size_t payload_length, uint8_t *result);
  void sha256_hmac(const uint8_t *payload, size_t payload_length, const uint8_t *key, size_t key_length, uint8_t *result);
  
  #endif
  