besu/docs/Privacy/Privacy.md

Privacy

Private Transaction

A transaction conforming to the definition of a restricted transaction as defined in the EEA Client Specification v2. The private payload is only stored within the nodes participating in the transaction and not in any other node. Private transactions are kept private between related parties, so unrelated parties have no access to the content of the transaction, the sending party, or the list of participating addresses. The sending actor is specified in the privateFrom attribute of the transaction. The receiving parties are specified in the privateFor attribute of the transaction. See eea_sendrawtransaction for implementation details.

Important Concepts

• Precompiled Contract: A smart contract compiled from its source language to EVM bytecode and stored by an Ethereum node for later execution.
• Privacy: It is “The right of individuals to control or influence what information related to them may be collected and stored and by whom and to whom that information may be disclosed.” For the purposes of this Specification, this right of privacy also applies to organizations to the extent permitted by law.
• Private State: Data that is not shared in the clear in the globally replicated state tree. This data can represent bilateral or multilateral arrangements between counterparties, for example in private transactions.
• Private Transaction: A transaction where some information about the transaction, such as the payload data, or the sender and recipient, is only available to the subset of network actors who are parties to that transaction.
• Private Transaction Manager: A subsystem of an Enterprise Ethereum system for implementing privacy known as an Enclave. e.g. Orion.
• Actor: The public key of someone involved in the private transaction (e.g. a privateFor actor).
• Privacy group id: A unique identifier associated with the set of actors that are involved in private transaction.

How Private Transaction is Processed

1. A private transaction is sent to the eea_sendrawtransaction endpoint, using the privateFor attribute to specify the list of actors, The privateFrom attribute specifies the sending actor, and restriction attribute is set to restricted.

2. The JSON RPC endpoint hands off the private transaction to a Private Transaction Handler.

3. The Private Transaction Handler sends the private transaction to an Enclave (Private Transaction Manager)

4. The Enclave will store the private transaction in map. The transaction will be associated with a random key (Enclave-key) identifying that transaction in the enclave and a privacy group id.

5. The Enclave distributes the private transaction point-to-point directly to the enclaves of actors specified in the privateFor attribute. All enclaves storing this transaction will associate it with the same key and privacy group id.

6. The Enclave returns the Enclave-key back to the Private Transaction Handler (as a response to the synchronous HTTP call).

7. The Private Transaction Handler will create a Privacy Marker Transaction (PMT). A PMT is a standard public Ethereum transaction. The payload of the PMT is the Enclave-key of the private transaction. The to attribute of the PMT the privacy precompile contract. The PMT is signed with the nodes default key. The PMT is sent to the transaction pool. Once the PMT has been mined in a block it is distributed to all nodes in the network.

8. The Transaction Processor of every node in the network will process the PMT as per any other public transaction. The PMT will be passed to the privacy precompile contract on those nodes that contain that precompile contract specified in the to attribute of the PMT.

9. The Privacy Precompile Contract queries the Enclave for the Private Transaction and Privacy Group Id based on the Enclave-key.

10. The Privacy Precompile Contract executes the Private Transaction using the Private Transaction Processor, specifying the private world state to use based on the Privacy Group Id. The Private Transaction Processor can read and write to the private world state, and read from the public world state.

Privacy JSON-RPC API method

The EEA methods created to provide and support privacy.

!!!note EEA methods are for privacy features. Privacy features are under development and will be available in v1.1.