Azimuth

Azimuth is a general-purpose public-key infrastructure (PKI) on the Ethereum blockchain, used as a platform for Urbit identities. You need such an identity to use the Arvo network.

The primary way to interact with Azimuth is through our Bridge application and the node libraries that it depends on, azimuth-js and urbit-key-generation. Take a look at the source and play around, or see Getting Started.

Arvo vs. Azimuth

Urbit is a project, not a single computer system. It has multiple components: Arvo, the operating system; and Azimuth, the identity system. Let's compare them.

Arvo is an operating system that provides the software for a personal server. These personal servers together constitute the peer-to-peer Arvo network. To make this network work on the social level, Arvo is built to work with a system of scarce and immutable identities.

Azimuth is the public-key infrastructure built to be such a system. A suite of smart-contracts on the Ethereum blockchain, Azimuth determines which Ethereum addresses own which Azimuth identities, called Urbit identities, or just identities. All identity-related operations, such as transfers, are governed at this layer. But Azimuth isn't built strictly for Arvo -- it could be used as a generalized identity system for other projects.

These otherwise-parallel systems meet when you want to connect to the Arvo network. Your Arvo personal server, called your ship, needs to be able to prove cryptographically that it is who it says it is. This proof comes in the form of a keyfile, derived from your identity, that you use to start your ship.

A metaphor might help illustrate the relationship between these two systems: the Arvo network is the neighborhood that you live in; Azimuth is the bank vault that stores the deed to your house.

The Urbit HD Wallet

Owners of Urbit identities need safeguards that allow for the use of Urbit without jeopardizing cryptographic ownership of their assets. Toward this end, we created the Urbit Hierarchical Deterministic (HD) Wallet for the storage of identities. The Urbit HD Wallet is not one key-pair, but a system of related key-pairs that each have distinct powers, from setting networking keys for communicating in the Arvo network to transferring ownership of identities.

The Urbit HD Wallet's derivation paths have a hierarchical structure, so that keys with different powers can be physically separated. A "master ticket" can re-derive the entire wallet in case of loss. The encryption and authentication keys that identities ships use to sign messages within the network are also derived from the wallet.

Urbit HD wallets are composed of the following items, which are each assigned to their own individual Ethereum key-pairs.

Master Ticket

Think of your master ticket like a very high-value password. The master ticket is the secret code from which all of your other keys are derived. Technically, your master ticket is seed entropy. You should never share it with anyone, and store it very securely. This ticket can derive all of your other keys: your ownership key and all of the related proxies.

Ownership Address

An ownership address has all rights over the assets deeded to it. These rights are on-chain actions described and implemented in the Ecliptic, Azimuth's suite of governing smart-contracts.

Proxies

Proxy addresses allow you to execute non-ownership related actions like spawning child identities, voting, and setting networking keys without jeopardizing the keys you've designated with ownership rights. Setting proxy rights is optional, but it is recommended for on-chain actions you will execute more frequently.

Most Ethereum tokens use the ERC-20 standard for smart contracts. Urbit identities are, however, essentially different from most Ethereum tokens, due to identities not being fungible. Since any two stars will handle social-networking realities in a different way, they will carry a different reputation. identities are to houses as tokens are to gold.

The ERC-721 standard, having been made specifically to provide a smart-contract interface for non-fungible assets, serves our needs well. This is the standard that we use for deeding Urbit identities.

identities, and all of their blockchain operations, are governed by the Ecliptic. The Ecliptic is an Ethereum smart-contract that governs identity state and the ownership, spawn, management, and voting rights affiliated with your identities.

For the technical implementation details, take a look at Azimuth's Github repository.