Aion is a smart contract blockchain emphasizing interoperability with existing blockchains and its own purpose-built sidechains. Aion smart contracts are written in the Java programming language, which allows developers to use related languages, such as Kotlin and Scala, ecosystem tools, and the extensive history of JVM relative to the EVM or WASM; this primer provides further detail on the technical differences between each approach. Like Ethereum, Aion’s architecture supports a virtual machine, the Aion Virtual Machine (AVM). The AVM features a JIT compiler that allows multi-threading of concurrent transactions to increase speed. Aion supports dApp development with Java toolkits such as Maven. Aion completed a token sale in October 2017, raising over $23 million. Aion is led by Matthew Spoke, the CEO of Nuco and board member of the Enterprise Ethereum Alliance (EEA). Aion development is managed by the Aion Foundation, a Cayman Islands-based non-profit.
In tandem with being a general-purpose smart contract platform, Aion also aims to enable interoperability with other public and private blockchains. Aion is a multi-chain network that allows developers to utilize sidechains that optimize desired features (i.e., scalability or privacy) without the network lock-in that may occur by choosing a purpose-built network. Other blockchains can connect to the primary Aion chain, Aion-1, provided they meet functionality and communication specifications including support for atomic swaps and facilitating an escrow period for cross-chain token transfers. Aion-1 will connect both to Aion sidechains designed for particular use cases and independent blockchain networks; blockchains such as Ethereum could connect to Aion in this manner. Cross-chain communication is facilitated by third parties in a ‘connecting network’, which will provide an interface for developers and users to route messages and transactions between networks. Nodes in this connecting network must stake AION tokens to participate. These networks must adhere to Aion’s specifications regarding valid inter-chain communication detailed above.
The first version of the Aion network used Proof of Work (PoW) mining for consensus but switched to a hybrid model, called Unity in November 2019 that uses both PoW and Proof of Stake (PoS), with PoW mining continuing to use the Equihash2109 algorithm. The AION token is used as ‘gas’ to pay computational fees to execute smart contracts and cross-chain transactions, with a gas fee market similar to Ethereum. Interchain validators must stake AION, which can be slashed if the node attempts to confirm invalid transactions. Since the upgrade to Unity, Aion's inflation rate is no longer fixed with issuance running at 3.01% in Year 1, falling to 2.69% by Year 5. Aion has a ten-second block time. The initial mainnet, Kilimanjaro, was released in April 2018, after a mainnet swap process to convert ERC20 Aion tokens. The Aion project split into two separate but collaborative projects in November 2019, the Aion blockchain and the Open Application Network (OAN) with the latter now focused on the development of open applications built atop Aion.