Design and implement encrypted data storage for node uptime/downtime #1
Description
Implement a system where each node encrypts its uptime/downtime records so that only the owner node can decrypt and modify them. Use asymmetric keypairs per node (e.g., Ed25519/X25519) and hybrid encryption (symmetric per record, key encrypted with owner's public key). Records should be signed for integrity.
- Generate and manage node keypairs securely.
- Define JSON schema for encrypted records (ciphertext, encrypted_key, nonce, signature).
- Implement encryption, signing, decryption, and verification routines.
- Add tests to ensure only owner can access their data.