Ocean Node is the core infrastructure component within the Ocean Protocol ecosystem, designed to facilitate decentralized data exchange and management. It operates by leveraging a multi-layered architecture that includes network, components, and modules layers. 
Key features include secure peer-to-peer communication via libp2p, flexible and secure encryption solutions, and support for various Compute-to-Data (C2D) operations. 
Ocean Node's modular design allows for customization and scalability, enabling seamless integration of its core services—such as the Indexer for metadata management and the Provider for secure data transactions—ensuring robust and efficient decentralized data operations.
### Architecture Overview
The Node stack is divided into the following layers:
* libp2p supports ECDSA key pairs, and node identity should be defined as a public key.
* Multiple ways of storing URLs:
* Choose one node and use that private key to encrypt URLs (enterprise approach).
* Choose several nodes, so your files can be accessed even if one node goes down (given at least one node is still alive).
* Use MPC to divide the key among multiple nodes (so no one node has the entire key).
* Protecting URLs during download: use a TEE enclave to decrypt the key (makes sense only for the MPC approach) and read content in the enclave.
* Supports multiple C2D types:
* Light Docker only (for edge nodes).
* Ocean C2D (Kubernetes).
* Each component can be enabled/disabled on startup (e.g., start node without Indexer).
### Nodes and Network Model
Nodes can receive user requests in two ways:
* HTTP API
* libp2p from another node
They are merged into a common object and passed to the appropriate component.
Nodes should be able to forward requests between them if the local database is missing objects. (Example: Alice wants to get DDO id #123 from Node A. Node A checks its local database. If the DDO is found, it is sent back to Alice. If not, Node A can query the network and retrieve the DDO from another node that has it.)
Nodes' libp2p implementation:
* Should support core protocols (ping, identify, kad-dht for peering, circuit relay for connections).
* For peer discovery, we should support both mDNS & Kademlia DHT.
* All Ocean Nodes should subscribe to the topic: OceanProtocol. If any interesting messages are received, each node is going to reply.
### Components & Modules
#### Indexer
An off-chain, multi-chain metadata & chain events cache. It continually monitors the chains for well-known events and caches them (V4 equivalence: Aquarius).
Features:
* Monitors MetadataCreated & MetadataUpdated and stores DDOs.
* Validates DDOs according to multiple SHACL schemas.
* Provides proof for valid DDOs.
* Monitors data token contracts & stores orders.
* Allows queries for all the above.
#### Provider
* Performs checks on-chain for buyer permissions and payments.
* Encrypts the URL and metadata during publishing.
* Decrypts the URL when the dataset is downloaded or a compute job is started.
* Encrypts/decrypts files before storage/while accessing.
* Provides access to data assets by streaming data (and never the URL).
* Provides compute services (connects to multiple C2D engines: light, Ocean C2D, third parties).
### Modules
#### MPC
Instead of encrypting with a private key, we can leverage MPC to construct the key, which is used for encrypting & decrypting URL and file contents.
#### TEE
Once a URL is decrypted (based on a consume request), the node operator can log that URL, and thus the asset is compromised.
We can move the entire encryption/decryption/MPC process to TEE, giving us full security regarding plain data.
A node that supports TEE should expose its proof in the status endpoint.
With MPC encryption (both assets & files), other nodes should refuse to reassemble the private key if the node does not expose & pass the proof check.
#### Light Docker C2D
Ocean C2D is flexible and scalable but has one major drawback: it requires Kubernetes.
For edge nodes (e.g., installed in a car, or a weather station running on Raspberry Pi), we can have a light engine that only uses the Docker system installed on the host. All orchestration (creating & provisioning input volumes, publishing results) can be handled by this module, while only the actual algorithm job is leveraged to Docker, with locally provisioned folders mounted.
