Glossary

A

account

A ledger account is a set of entries in the ledger canister, which is a smart contract that mimics the guise and behavior of a regular banking account, whose unit of measure is ICP (Internet Computer Protocol) utility tokens. Ledger accounts are owned by principals, and their ownerships do not change over time. Every account on the ledger has a positive balance measured in ICP with a precision of eight decimals.

address

In the context of transactions on the ledger, address is synonymous with account.

B

balance

The balance of an account on the ledger is the sum of all deposits minus the sum of all withdrawals. As a degenerate case, it is sometimes useful to say that an account which is not present in the ledger has a balance of zero.

The balance of a ledger account is denominated in ICP and is represented with eight decimals. Thus, the minimum positive balance of an account is 0.00000001 or 10^-8 ICP; this amount is sometimes referred to as one e8.

batch

A batch is a collection of messages whose order is agreed upon by consensus.

beneficiary

The beneficiary of an account is the principal who owns the balance of the account. The beneficiary of an account cannot be changed. The beneficiary of an account may or may not be allowed to make transactions on the account (see fiduciary).

blockchain

A blockchain is a growing list of cryptographically linked blocks, agreed upon by consensus. On the Internet Computer every subnet is a blockchain and these blockchains interact using chain key cryptography.

burning transaction

A burning transaction is the process of "burning" ICP, whereby a certain amount of ICP are destroyed. The main use case is that of purchasing cycles, through which ICP are destroyed while at the same time a corresponding amount of cycles is created, using the current exchange rate between ICP and ( SDR), in such a way that one SDR corresponds to one trillion (10E12) cycles. It is represented as a transaction from the source account to the ICP supply account.

C

canister

A canister is a computational unit that bundles code and state. A canister can be deployed as a smart contract on the Internet Computer and accessed over the Internet.

canister account

A canister account is a ledger account owned by a canister (i.e. whose fiduciary is a canister). A non-canister account is a ledger account whose fiduciary is a non-canister principal.

canister identifier

The canister identifier or canister ID is a globally-unique identifier that identifies a canister and can be used to interact with it.

canister signature

A canister signature uses a signature scheme based on certified variables. Public “keys” include a canister id plus a seed (so that every canister has many public keys); signatures are certificates that prove that the canister has put the signed message at a specific place in its state tree. Details in the The Internet Computer Interface Specification.

canister state

A canister state is the entire state of a canister at a given point in time. A canister’s state is divided into user state and system state. The user state is a WebAssembly module instance and the system state is the auxiliary state maintained by the Internet Computer on behalf of the canister, such as its compute allocation, balance of cycles, input and output queues, and other metadata. A canister interacts with its own system state either implicitly, such as when consuming cycles, or through the System API, such as when sending messages.

catch-up package (CUP)

A catch-up package is a data bundle that contains everything needed to bootstrap a subnet replica.

certified query

A certified query is a query call for which the response is certified.

certified variable

A piece of data that a canister can store in its subnet’s canonical state in the processing of an update call (or inter-canister call), so that during the handling of a query call, the canister can return a certificate to the user that proves that it really committed to that value.

chain key

Chain key cryptography consists of a set of cryptographic protocols that orchestrate the nodes that make up the Internet Computer. The most visible innovation of chain key cryptography is that the Internet Computer has a single public key. This is a huge advantage as it allows any device, including smart watches and mobile phones, to verify the authenticity of artifacts from the Internet Computer.

consensus

In distributed computing, consensus is a fault tolerant mechanism by means of which a number of nodes can reach agreement about a value or state.

Consensus is a core component of the replica software. The consensus layer selects messages from the peer-to-peer artifact pool and pulls messages from the cross-network streams of other subnets and organizes them into a batch, which is delivered to the message routing layer.

controller

A controller of a canister is a person, organization, or other canister that has administrative rights over the canister. Controllers are identified by their principals. For example, a controller of a canister can upgrade the WebAssembly code of the canister or delete the canister.

D

dapp

A dapp, or decentralised application is a canister smart contract running on the Internet Computer.

R

replica

The replica is a collection of protocol components that are necessary for a node to participate in a subnet.