## Synopsis

Alphabetical list of terms commonly use in a NOCUST system with brief explanation.

### Motivation

Quick reference for researcher, implementers and people learning about the protocol.

### Desired Properties

(desired characteristics / properties of protocol, effects if properties are violated)

Clear and concise explanation of the terms specific to NOCUST. For additional details, refer to the appropriate spec document.

## Technical Specification

#### Account

A user account in NOCUST is unique for a given parent-chain address and asset token address. The owner of the account is the person knowing the private key behind the parent-chain-address. The account can have several accounts for a given address for each asset token.

#### Asset token

Fungible token that comply with a token standard. The token should implement a standard interface for transfer function, transfer allowance function and balance function (ERC20 in Ethereum).

#### Eon

Period in number of blocks between each NOCUST commitment. Also called round.

#### Epoch

Quarter of an eon.

Third of an eon.

#### Era

Block number of the current eon.

#### Finalization (Swap)

A fully matched swap can be finalized. After the finalization the balances of the accounts involved are effectively credited and debited. The account is unlocked and the balances can be spent.

#### Finalization (Transfer)

A finalized transfer has its passive marker set to its actual value in the active tree. Previous to the finalization the passive marker is equal to $2^{256} - 1$. The finalization is required when the user wants to make a followup transfer or swap. This means that only the last transaction in the set of the active tree is no finalized.

#### Native asset token

Native token of the parent-chain used to pay transaction fees (Ether in Ethereum).

#### Offset

In the context of an interval tree, the offset of a leaf element is its left value. See specification of interval trees for a more detailed explanation.

#### Operator

Operator of the NOCUST system. Runs a dedicated server to facilitate off-chain transactions, process registrations, deposits and withdrawals. Has access to special method on the NOCUST smart-contract (contract owner). Submits checkpoints and is responsible to answer challenges.

#### Operator endpoint

Operator API used by the user to interact with the operator.

#### Passive Marker

The passive marker of a transfer is the left value or (offset)[#offset] of the last outgoing transfer in the passive interval tree of its recipient.

#### Recovery

Frozen state of the commit-chain when the operator fails to reply a challenge or misses a checkpoint submission. No more operations are possible beside the user withdrawing their funds. Once in recovery, the commit-chain stays in this state indefinitely.

#### Registration

Required procedure in order to open an account at the commit chain.

#### Swap

Swap refers to a type of transaction involving 2 accounts of the same owner but of different asset token. One account is debited a certain amount and the other is credited a certain amount.

#### Transfer

Unless specified otherwise, a transfer refers to a type of transaction involving a sender and a recipient (i.e simple money transfer across accounts).

#### Transaction

Unless specified otherwise, transaction refers to a NOCUST transaction of type transfer or swap.

## History

03.08.19 - Initial writeup