Avalanche is a
decentralized,
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
proof of stake blockchain
A blockchain is a type of distributed ledger technology (DLT) that consists of growing lists of records, called ''blocks'', that are securely linked together using cryptography. Each block contains a cryptographic hash of the previous block, ...
with
smart contract
A smart contract is a computer program or a transaction protocol that is intended to automatically execute, control or document events and actions according to the terms of a contract or an agreement. The objectives of smart contracts are the re ...
functionality. AVAX is the native
cryptocurrency
A cryptocurrency, crypto-currency, or crypto is a digital currency designed to work as a medium of exchange through a computer network that is not reliant on any central authority, such as a government or bank, to uphold or maintain it. It i ...
of the platform.
History
Avalanche began as a protocol for solving for
consensus in a network of unreliable machines, where failures may be crash-fault or
Byzantine
The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...
. The protocol's fundamentals were first shared on the
InterPlanetary File System (IPFS) in May 2018 by a pseudonymous group of enthusiasts going by the name "Team Rocket".
Avalanche was later developed by researchers from
Cornell University
Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to teac ...
led by
Emin Gün Sirer
Emin Gün Sirer is a Turkish-American computer scientist. Sirer developed the Avalanche Consensus protocol underlying the Avalanche blockchain platform, and is currently the CEO and co-founder of Ava Labs. He was an associate professor of comput ...
and doctoral students Maofan "Ted" Yin and Kevin Sekniqi.
Following the research stage, a startup technology company was founded to develop a blockchain network that would meet finance industry requirements.
In March, 2020, the AVA codebase (Developer Accelerator Program or AVA DAP) for the Avalanche consensus protocol was released as
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
and became available to the public.
In September, 2020, the company also issued its native token Avax.
Design
AVAX
Avalanche (AVAX) is the native token of Avalanche, traded on the X-Chain.
Protocol
The protocol has four basic interrelated mechanisms that compose structural support of the consensus tool. These four mechanisms are Slush, Snowflake, Snowball, and Avalanche. By using randomized sampling and metastability to ascertain and persist transactions, It represents a new protocol family. Although the original paper focused on a single protocol, namely Avalanche, it implicitly introduced a broad spectrum of voting-based, or
quorum-based consensus protocols, called the Snow family.
While Avalanche is a single instantiation, the Snow family seems to be able to generalize all quorum-based voting protocols for replica control. Unlike prior quorum-based work, the Snow family enables arbitrarily parametrizable failure probability at the quorum intersection level. Standard quorum-based protocols define this failure probability to be precisely zero, but by introducing errors in the quorum intersection, a larger set of consensus protocol design is available.
Background
Consensus protocols are the basis for the
state machine replication problem, which aims to enable a set of machines to achieve agreement over a network even when a subset of the machines are corrupted. There are two major families of consensus protocols to date - classical consensus and Nakamoto consensus protocols. The first achieves consensus through
quorums, thus requires voting. Famous instantiations of this are
Paxos
Paxos ( gr, Παξός) is a Greek island in the Ionian Sea, lying just south of Corfu. As a group with the nearby island of Antipaxos and adjoining islets, it is also called by the plural form Paxi or Paxoi ( gr, Παξοί, pronounced in Engli ...
(in the crash-fault-tolerant environment) and PBFT
in the Byzantine-fault tolerant case. These protocols achieve agreement in a similar operation to a parliament: a proposal (transaction) is proposed and voted on to be accepted or rejected. If sufficient votes cast by the various replicas are accumulated (typically collected through elected leader replica), then a quorum is achieved, and thus agreement.
The second family, pioneered by
Satoshi Nakamoto
Satoshi Nakamoto is the name used by the presumed pseudonymous person or persons who developed bitcoin, authored the bitcoin white paper, and created and deployed bitcoin's original reference implementation. As part of the implementation, Nakam ...
and
Bitcoin
Bitcoin (abbreviation: BTC; sign: ₿) is a decentralized digital currency that can be transferred on the peer-to-peer bitcoin network. Bitcoin transactions are verified by network nodes through cryptography and recorded in a public distr ...
is that of Nakamoto consensus. Unlike quorum-based protocols, machines operating an instance of Nakamoto consensus achieve agreement on transactions by downloading the longest chain (typically called a
fork
In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tine (structural), tines with which one ...
). In
Bitcoin
Bitcoin (abbreviation: BTC; sign: ₿) is a decentralized digital currency that can be transferred on the peer-to-peer bitcoin network. Bitcoin transactions are verified by network nodes through cryptography and recorded in a public distr ...
, the longest chain is verified by ensuring that it is the one with the highest degree of work (or
proof of work
Proof of work (PoW) is a form of cryptographic proof in which one party (the ''prover'') proves to others (the ''verifiers'') that a certain amount of a specific computational effort has been expended. Verifiers can subsequently confirm this expe ...
).
Snow, while quorum-based, seems to be a universal generalization of all quorum-based protocols. Unlike prior work which requires that quorums be deterministic, i.e. the failure probability is precisely zero, Avalanche loosens this requirement, thus enabling quorum-based protocols to estimate global network state ''with errors''.
Assumptions
While the Snow family can be theoretically generalized to all classes of assumptions that quorum-based protocols have previously made, the formalization paper analyzes Avalanche under an asynchronous network in the Byzantine setting.
The assumptions are as follows:
Processors
* Processors operate at arbitrary speed.
* Processors may experience arbitrary failures, even Byzantine ones.
* Processors with stable storage may re-join the protocol after failures.
* Processors can collude, lie, or otherwise attempt to subvert the protocol. (That is,
Byzantine failures are permissible.)
Network
* Processors can send messages to any other processor.
* Messages are sent asynchronously and may take arbitrarily long to deliver.
* Messages may be lost, reordered, or duplicated.
* Messages are delivered without corruption, i.e. an adversary cannot forge digital signatures.
Safety and liveness properties
The Snow family generalizes the typical definitions of safety and liveness encountered in quorum-based protocols. For Avalanche specifically, these properties are:
; Agreement (or ''consistency'', or ''safety'')
: If any node (or machine) finalizes a value *v*, no other node will finalize another value *u* that conflicts with *v* with probability higher than $\epsilon$.
; Termination (or liveness)
: If network resumes synchronous operation, then all nodes will achieve agreement.
Avalanche, like other asynchronous networks, is not guaranteed to terminate and thus does not have the liveness property, during asynchrony. Like Paxos, Avalanche's goal is to ensure fault tolerance and it guarantees safety under asynchrony, but not liveness. This is in contrast to Nakamoto consensus, which guarantees liveness, and not safety under asynchrony.
See also
*
Fault-tolerant computer system
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
*
Replication (computing)
Replication in computing involves sharing information so as to ensure consistency between redundant resources, such as software or hardware components, to improve reliability, fault-tolerance, or accessibility.
Terminology
Replication in com ...
*
Paxos
Paxos ( gr, Παξός) is a Greek island in the Ionian Sea, lying just south of Corfu. As a group with the nearby island of Antipaxos and adjoining islets, it is also called by the plural form Paxi or Paxoi ( gr, Παξοί, pronounced in Engli ...
*
Virtual synchrony
*
Raft
A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barrels ...
*
Chandra–Toueg consensus algorithm The Chandra–Toueg consensus algorithm, published by Tushar Deepak Chandra and Sam Toueg in 1996, is an algorithm for solving consensus in a network of unreliable processes equipped with an ''eventually strong'' failure detector. The failure det ...
References
{{DEFAULTSORT:Avalanche Algorithm
Distributed algorithms
Fault-tolerant computer systems
Data synchronization
Network protocols
Internet properties established in 2018
2018 software
Currencies introduced in 2018