Software Architecture

Overview

The Enigma Network offloads private computation tasks from Ethereum. These tasks are initiated by the end users of Ethereum dAppDapps. A JS client library gives dAppDapp developers the tools to: 1) safely encrypt sensitive data in-memory for immediate use or storage; 2) obtain an authoritative proof that the target worker is securely running trusted hardware (SGX) prior to sending data and paying fees.

Upon receiving a computation task, the Enigma Contract deployed on-chain broadcasts the task in the Enigma network. Then, each registered worker runs a random sampling lottery to determine whether they should execute the task. This lottery is seeded with a random number generated using the trusted hardware’s true randomness module. Each network participant may independently run a pseudo-random algorithm to derive the selected worker. This is how the dApp knows which worker to verify.

Giving Out Computation Task Overview

The selected worker then instructs its trusted hardware to unpack the task, decrypt its arguments and delegate execution to its internal EVM. After execution, a hash of the task attributes (i.e. inputs, code and outputs) is signed with a private key that exists only in the trusted hardware. This data is then committed on-chain where its provenance and integrity are cryptographically verified. This on-chain verification guarantees: 1) integrity of the task attributes; 2) safe execution within trusted hardware; 3) execution by the selected worker. Finally, the results are relayed to the dApp contract and the worker collects its fee.

Executing Computation Task Overview

Subsystem Decomposition

The system is comprised of the following subsystems. A subsystem is a service provider that performs one function or many functions, but does nothing until it is requested.

  1. Registration:

    When a new node joins the network, it must register as a worker. The registration protocol ensures that the node runs on SGX hardware. It includes the node in a registry on-chain.

  2. Encryption / Storage:

    Data flows privately between the dApp and the Enigma Network using an Elliptic-curve Diffie–Hellman (ECDH) key agreement protocol. Encrypted data may be stored in the dApp contract state for future computation.

  3. Worker Selection:

    Multiple nodes participate in the network with the incentive of earning rewards by executing computation tasks as a worker. Worker selection happens for each computation tasks. Each node determines whether it is the selected worker by running an algorithm that relies upon a shared random seed.

  4. Computation:

    A computation task flows from the dApp users to the secure enclave through multiple components. It executes a function of the dApp smart contract with encrypted inputs.

  5. On-chain Verification:

    The Enigma Contract verifies signed data submitted by a node in the Enigma Network.

  6. Attestation:

    A dApp may verify the authenticity of the selected worker through a remote attestation protocol prior to requesting or a computation task.

Logical Components

The Enigma Network is not a standalone program. Its decentralized nature and tight coupling with Ethereum increase complexity by requiring the architecture to be molded according to highly opinionated existing components. Here are the key components that compose the system.

  1. Enigma Library (EnigmaP.js):

    A JavaScript library that performs the Enigma functions, to be included inside of dApps.

  2. dApp Contract:

    A smart contract created by the dApp author that stores encrypted data, the business logic of computation tasks and handles the callback.

  3. Enigma Contract:

    A smart contract deployed on the Ethereum Network that orchestrates on-chain operations of the Enigma Network.

  4. Surface:

    The untrusted component of an Enigma node whose primary function is to coordinate computation tasks between the Enigma Contract and Core.

  5. Core:

    The trusted component of an Enigma node that executes computation tasks. Core runs inside an SGX enclave.

  6. Principal Node:

    A temporary centralized node that propagates random numbers to the rest of the network.

  7. Attestation Service:

    A standalone service (not packaged in the local network) that verifies quotes with Intel.

The diagram below presents a composite view of the logical components of the system.

Composite Structure of the System

Composite Structure of the System

Mapping Between Subsystems and Logical Components

Given the complexity factor alluded to above, there is not a one-to-one mapping between the subsystems and logical components, this table illustrates in which component the core business logic of each subsystem is implemented.

  Eng Lib dApp Contract Eng Contract Surface Core
Registration     X   X
Encryption / Storage X X     X
Computation     X X X
Worker Selection     X X  
On-Chain Validation     X   X
Attestation X   X