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Access Logs

Access logs are cryptographically-signed logs designed to be tamper-proof.

That doesn’t sound crazy at all—it’s actually a brilliant security measure! 🔒 Cryptographically signing access logs would ensure integrity and authenticity, preventing attackers (or even internal users) from tampering with access records.

How to Implement Log Signing​

To ensure logs are tamper-proof, we can use public-key cryptography (asymmetric encryption) or hash-based integrity checks.

1. Digital Signatures (Best for Strong Security)​

  • Generate a public-private key pair (e.g., using RSA or ECDSA).
  • The microcontroller signs each log entry using the private key.
  • If someone modifies the log, the signature verification (done later) will fail.
  • Later, you (or a verification system) can use the public key to verify that logs were not altered.

2. HMAC (Hash-based Message Authentication Code) (Lighter but Secure)​

  • Instead of asymmetric encryption, use a secret key to generate an HMAC (e.g., HMAC-SHA256) for each log entry.
  • This prevents tampering unless someone gets the secret key.
  • Lighter on microcontrollers but not as strong as digital signatures.

3. Blockchain-style Hash Chaining (Forensic-Proof)​

  • Each log entry contains a hash of the previous log, creating a chain.
  • If someone modifies an entry, the entire chain breaks, making tampering detectable.
  • Can be combined with digital signatures for ultimate security.

Example Log Entry (Using RSA Signatures)​

{
    "timestamp": "2025-03-08T12:34:56Z",
    "user": "RFID_12345",
    "event": "Access Granted",
    "signature": "MEUCIQDx...XEXzA=="  // RSA signature
}

A separate tool (or your future house’s monitoring system 😉) can verify logs using the public key.

Next Steps​

  1. Do you prefer RSA (asymmetric, highly secure) or HMAC (lighter, but secret key-based)?
  2. Would you like me to update your documentation with log signing implementation?
  3. Would you like an Arduino/ESP32 code snippet for signing logs? 🚀