API Documentation for the NezertronixPro Crypto Platform: Cryptographic Protocols for External Database Synchronization

Core Cipher Specifications for Sync Sessions

The NezertronixPro Crypto Platform mandates a hybrid encryption scheme for all external database synchronization. The protocol uses X25519 for key agreement and AES-256-GCM for symmetric bulk data encryption. Every sync session begins with an ephemeral X25519 key exchange; the server generates a new key pair per connection, signs its public key with Ed25519, and transmits the signature along with the public key. The client must verify this signature using the platform’s pre-distributed root certificate. Once the shared secret is derived, both sides derive separate encryption and authentication keys using HKDF-SHA256 with a domain-specific salt.

Data blocks are encrypted with AES-256-GCM using a 12-byte nonce. Nonces are sequential per session, starting from a random offset, to prevent replay attacks. The authentication tag is 16 bytes. If decryption or tag verification fails, the entire sync batch is rejected and the connection is terminated. The platform logs the failure event with a unique error code, but does not expose plaintext reasons to the client to avoid side-channel leakage.

Integrity Verification via Merkle Trees

Beyond per-record authentication tags, the protocol requires a Merkle tree hash of the entire dataset being synchronized. The root hash is computed by the server and sent as part of the session handshake. The client recalculates the root hash after receiving all records and compares it. Mismatch triggers a full resync. This prevents partial data corruption or malicious insertion of records without detection.

Key Rotation and Revocation Mechanisms

External databases must rotate their signing keys every 90 days. The NezertronixPro API provides a dedicated endpoint (`/v2/keys/rotate`) that accepts a new Ed25519 public key signed by the previous private key. If the previous key is compromised, a revocation request must be submitted through the admin console with a hardware-backed attestation. The platform maintains a public key pinning list; any key not on this list is rejected within 5 seconds.

For session keys, the protocol enforces a maximum lifetime of 15 minutes. After that, a new X25519 handshake is required. This limits the blast radius of a compromised session key. The client must implement timer-based rekeying; the server sends a `RekeyRequired` signal 30 seconds before expiry.

Network-Level Protections and Error Handling

All sync traffic must use TLS 1.3 with a minimum cipher suite of TLS_AES_256_GCM_SHA384. The platform blocks any connection using TLS 1.2 or earlier. Additionally, the API enforces IP whitelisting for external database endpoints. Each request must include a timestamp and a nonce, hashed with HMAC-SHA256 using the derived session key. This prevents replay attacks at the transport layer.

Error responses are standardized: a JSON object with fields `error_code` (integer), `error_message` (short string), and `retry_after` (seconds). Common codes include 1001 (signature verification failed), 1002 (key rotation overdue), and 1003 (Merkle root mismatch). Clients must implement exponential backoff for retries, starting at 1 second and doubling up to 64 seconds.

FAQ:

What happens if the Merkle root hash mismatches?

The client must discard all received data and initiate a full resync from the last known good checkpoint. No partial records are accepted.

Can I use a static key pair for multiple sync sessions?

No. Each session requires an ephemeral X25519 key pair. Only the signing keys (Ed25519) for authentication can be reused within their 90-day validity window.

How are nonces generated for AES-256-GCM?

Nonces are sequential, starting from a random 12-byte value chosen by the server at session start. The client tracks the counter and rejects nonces out of order.

Is TLS 1.2 supported for backwards compatibility?

No. Only TLS 1.3 with TLS_AES_256_GCM_SHA384 is permitted. Connections using older TLS versions are immediately terminated with error code 2001.

What is the maximum size of a single sync batch?

The API allows up to 10,000 records per batch. Larger datasets must be split into multiple batches, each with its own Merkle tree root.

Reviews

Marcus V.

Implemented the API for our PostgreSQL replica. The X25519 handshake is fast, and the Merkle tree check caught a corrupted row immediately. Saved us hours of debugging.

Linda K.

The key rotation endpoint is straightforward. We automated it with a cron job that rotates our Ed25519 keys every 80 days. No downtime so far.

Raj P.

We had a TLS misconfiguration that blocked sync. The error codes were precise, and the retry logic worked perfectly after we fixed the cipher suite. Solid documentation.