Appendix

ContributorsPermalink

The Obscuro project is decentralised in nature, and this whitepaper has benefited enormously with feedback from the following contributors:

• Richard Gendal Brown

• Mike Hearn

• Moritz Platt

• Tim Brinded

• Fred Dalibard

• Stefan Iliev

• Zbigniew Czapran

Additional feedback is welcome, and all reviewers will be credited.

GlossaryPermalink

Aggregator A node that participates in an L2 network and collaborates with other Aggregator nodes to manage the L2 contracts and confirm correctness of transactions. Specifically, it participates in transaction gossip, and may propose transaction rollups to be registered with the L1 blockchain.

Attestation Constraints Means of controlling which software is allowed to run inside the Trusted Execution Environment.

Automated Market Maker / AMM Uses liquidity pools to allow digital assets to be traded automatically and without permissions.

Block Reward An amount of OBX which is given to node operators to cover their costs to validate and publish blocks.

Enclave Key / EK Collection of one or more cryptographic keys used for encrypting and decrypting data unique to a specific enclave, digitally signing data and identifying a Trusted Execution Environment.

ERC-20 Ethereum Request for Comments 20, proposed by Fabian Vogelsteller in November 2015, is a token standard that implements an API for tokens within Smart Contracts.

Ethereum Virtual Machine / EVM A virtual computer whose existence is maintained by thousands of connected real-world computers running an Ethereum client.

Gas The unit that measures the amount of computational effort required to execute specific operations on the Ethereum network.

Gas Price The levy imposed for every computation executed on the Ethereum network to encourage good behaviour, e.g. prevent bad actors from spamming the network.

Genesis Enclave The first Trusted Execution Environment to join a new network. The Genesis enclave propagates the master seed to the other attested nodes by encrypting it with specific Trusted Execution Environment keys.

Host The party controlling the physical server that runs the Trusted Execution Environment. In the threat model of typical confidential computing applications, including Obscuro, the host is an adversary of the system.

L1 Management Contract The smart contract that runs on Ethereum and handles all L1 concerns.

Layer 1 / L1 The public Ethereum blockchain and network.

Layer 2 / L2 A second network built on top of an L1 network and dependent on it. An L2 network expands on the capabilities of the L1 network by increasing capacity or enhancing functionality.

Maximal Extractable Value / MEV Participants in the network may extract value by observing user transactions and then preempting them by inserting their own transaction ahead in the processing queue and influencing the price of an asset in order to extract a profit.

Non-Fungible Token / NFT A unique and non-interchangeable unit of data stored on a digital ledger.

Obscuro Public Events Special events emitted by L2 contracts that are included in the rollups in plaintext, and are exposed to L1 contracts once rollups reach finality. It is a mechanism by which Obscuro can publish information.

OBX The utility token used by Obscuro.

Off-Chain Activity happening away from the Layer 1 blockchain.

Optimistic Rollup Optimistic rollups assume that all transactions are valid and submit batches without performing any computation. They include a challenge period during which anyone can dispute the legitimacy of the data contained in a batch. If a fraudulent transaction is detected, the rollup executes a so-called fraud proof and runs the correct transaction computation using the data available on Layer 1.

Over-the-counter / OTC A venue to provide bespoke financial agreements or options negotiated between counterparties as opposed to being listed on an exchange.

Patricia Tree Root A Patricia Tree (or Trie), is a data structure used in the Ethereum model to represent the receipt trie, the world state trie, the account storage trie, and the transaction trie. Only the root node of the trie is stored in the ethereum block, and it represents a single cryptographic proof for the entire state.

Proof Of Block Inclusion / POBI Obscuro’s novel decentralised round-based consensus protocol based on a fair lottery and on synchronisation with the L1 designed for L2 rollups.

Rollup L2 solutions that perform transaction execution outside the main L1 chain, but post transaction data on L1. A rollup is a batch of transactions that were executed by the L2 Verifiers.

Root Provisioning Key / RPK A cryptographic key randomly created and retained by Intel. It is the basis for how the processor demonstrates that it is a genuine Intel SGX CPU at a specific trusted computing base.

Root Sealing Key / RSK A cryptographic key that is unique to an enclave which that enclave uses to encrypt and decrypt data stored outside the enclave boundary.

Sequencer A sequencer is the selected Aggregator which builds a rollup in a round.

SGX Software Guard Extensions, a technology provided by Intel, a major CPU manufacturer. An SGX CPU has an area for encrypted computation, which the operator cannot access, secured by a private key burnt into the CPU during manufacture.

Smart Contract / Contract A user application running on a blockchain network which holds data or state, responds to user commands, and may store and manage assets or money.

Stake A non-negligible amount of value which is given over to an activity or process to demonstrate commitment to follow the rules for that activity or process.

Trusted Execution Environment / TEE An environment where contracts may be managed in a deterministic, repeatable and auditable way, based on a set of trust dependencies.

Trusted computing base / TCB The set of computing technologies that must be working correctly and not be malicious or compromised for a security system to operate.

Utility Token Tokens which are intended to provide digital access to an application or service.

Verifier A light L2 node which observes transaction rollups published to the L1 blockchain, and can participate in possible disputes. Any Verifier can become an Aggregator by registering on the L1 contract and pledging some stake.

ZK-rollups Zero knowledge rollups generate cryptographic proofs that can be used to prove the validity of transactions.