Cryptoworld: AION MULTI-TIER BLOCKCHAIN NETWORK

The Protocol

The Aion protocol enables the development of a federated blockchain network, making it possible to seamlessly integrate dissimilar blockchain systems in a multi-tier hub-and-spoke model, similar to the internet.

Aion the third-generation blockchain

In the future, blockchains will federate data and value in a hub and spoke model similar to the internet. The future of mainstream blockchain adoption will be achieved by the development of a networked, federated blockchain to integrate these separate spokes.
That integrated blockchain network is Aion.

Aion is a third-generation blockchain network that will enable any private or public sector organization to:

• Federate: Send data and value between any Aion-compliant blockchain and Ethereum.

• Scale: Provide fast transaction processing and increased data capacity to all Aion blockchains.

• Spoke: Allow the creation of customized public or private blockchains that maintain interoperability with other blockchains, but allow publishers to choose governance, consensus mechanisms, issuance, and participation.

At the root of the Aion network is a purpose-built, public, third-generation blockchain called Aion-1. Designed to connect other blockchains and manage its own robust applications, Aion-1 also provides the economic system that incentivizes interoperability in the ecosystem.

AION tokens are the fuel used to create new blockchains, monetize inter-chain bridges, and secure the overall network.

AION MULTI-TIER BLOCKCHAIN NETWORK

The Aion multi-tier blockchain network is like a computer network, providing a protocol and standard for dissimilar systems to communicate.
However, in addition to information, the Aion network will pass logic and value among participating blockchains to create a contiguous value chain where every transaction occurs on-chain, with logic and value passing among chains as freely as liquid assets.

Figure 1:Example of a simple Multi-Tier Blockchain Network network, consisting of all the major actors

These infrastructures, protocols, and concepts will work together to guarantee transmission from an origin to its destination through interchain communication.

The value of these technologies is that they enable one blockchain to transact with another blockchain, as well as one blockchain to transact with every connected blockchain.

Connecting Networks

Connecting networks are networks that facilitate interchain communication and interchain transactions between multiple private or public blockchain networks. Connecting networks are defined by requirements that specify their role within the context of the Aion network.

Connecting networks and interchain transactions provide a universal interface that enables blockchain developers and users to route messages from one network to another.

Specifically, a connecting network should provide the following core functionalities:

• Route messages between different blockchain networks through a common bridging protocol that involves translation and propagation of the message, which must be considered final.

• Provide decentralized accountability.

• Provide a bridging protocol.

Aion network protocols specify standards for the external components. While the actual functionality and internal components of each connecting network might vary by vendor and intended purpose, these core functionalities should be implemented.

Point-to-point connections such as inter-blockchain relays or purpose-specific networks such as BTC Relay exist as central hubs. Such protocols, while simple and efficient, often result in complicated state channels that can give rise to contentious situations and are often at the mercy of one or a select group of individuals that run the relaying networks.

A connecting network instead uses bridges and a trust-free blockchain network to validate and ensure the correctness of flowing transactions. By introducing a third party that routes messages from point A to point B, the networks themselves do not have to manage difficult or unclear situations.

Format

Ideally, the interchain transaction format would include three parts:

• Payload data that is specific to the creator and is typically regular transaction data, but potentially could be extended to arbitrary data, at the discretion of the creator and the source network.

• Metadata about the interchain transaction that contains routing information and fees.

• Merkle proof that is only used when the sender wants to bypass the bridge.

The bridge and connecting network validators shall not interpret the data, but do check the integrity of the transaction as a whole. Privacysensitive information applications could choose to encrypt the data if necessary.

Routing

The routing of interchain transactions is a multi-phase process. In each phase, the validators verify the transaction and reach consensus on whether the transaction should be forwarded or rejected.

If a transaction gets rejected at any point, any state change as a result of the interchain transaction will be reverted, at least in the connecting network.

The routing path can be divided into two subpaths: the forward path and backward path. In the forward path, an interchain transaction flows from the source chain all the way to the target chain. In the backward path, a confirmation of the interchain transaction is passed back.

Participating Networks

One of the core concepts in the Aion network design is that it is dedicated to the federation of compatible blockchains or blockchainrelated networks. These can be purpose-specific blockchains, private networks, or consortium blockchains representing collections of entities.

Regardless of the context, the interconnectedness and the ability to interoperate in an efficient, secure, and transparent manner increases the value of each network individually and also provides stability to the blockchain ecosystem in general.

A participating network is any network that has successfully implemented requirements to integrate with the connecting network. Participating networks should be blockchains, but are not necessarily limited to such. Some useful participants could be oracles, cryptlets [3], or database clusters in need of verifiable information. The only limitation is the flexibility of the participating network to integrate with the connecting network.

Once integrated with the Aion network, participating networks gain access to the communication protocol (interchain transaction) specified earlier, enabling numerous possible use cases.

Participating networks have the full flexibility to customize different modules of their blockchain infrastructure including the consensus algorithm, hashing algorithm, virtual machine (VM), and scripting languages.

AION Compliant Blockchains

Aion-compliant blockchains refer to the participating blockchains that comply with the Aion protocol and on which bridges can be established easily to forward interchain transactions through Aion-1.

To be Aion-compliant, a blockchain must meet certain requirements including:

• Be decentralized in some fashion and support procedures commonly found in blockchains such as atomic broadcast and transactions. The exact implementation is left to the discretion of the bridging protocol and the network itself.

• Be able to recognize interchain transactions as distinct from regular transactions.

• Be aware of the consensus protocol used by the bridge and store a transaction deemed valid.

• Implement locktime or a similar feature that allows tokens to be held by the network for a period of time. Blockchain vendors will be able to adapt their offerings to be Aion-compliant. The Nuco blockchain infrastructure will be among the first Aion-compliant networks. More specific details on the requirements will be published as the project progresses.

Existing network compatibility

Unlike Aion-compliant blockchains, existing blockchains are not designed to be interoperable. To enable interchain transaction routing between the Aion network and existing blockchains, additional assumptions and/or compromises are required. In this section, we discuss the possibility of connecting the Ethereum blockchain to the Aion network.

AION to Ethereum

As part of the bridge protocol, a lightweight BFT-based consensus algorithm is used by the bridge validators. In Aion connecting networks, these BFT votes are natively aggregated and processed by the blockchain validators. The Ethereum blockchain does not have this built-in functionality, so it needs an interchain transaction contract.

In this model, the interchain transaction contract will synchronize the public keys of bridge validators periodically, depending on the Aion network specification. When an interchain transaction is requested, the bridge validators sign for it with their private key and send the signature to the interchain transaction contract.

The interchain transaction contract will collect all the votes (signatures) and provide a provable record of the event that contains the interchain transaction data and voting information. If at least two thirds of votes have been received, the bridge validators will use the record as evidence when confirming the interchain transaction.

Because the computation cost of multi-signature verification is high in the Ethereum blockchain (3,000 gas for a single ECDSA), a higher bridge fee is expected. To reduce this cost, a blockchain with full BFT functionality may be used in the bridge and only the outcome of voting will be stored on the Ethereum blockchain.

Ethereum to AION

Sending interchain transactions from the Ethereum blockchain to the Aion network is easier because of Ethereum’s programmable transaction size. Transactions intended for other blockchains will need to incorporate routing information in the data field.

There are two possible scenarios that can occur from an Ethereum interchain transaction (interchain transaction from the Ethereum blockchain to the Aion network), depending on the receiving address. If the transaction is sent to an externally-owned account, the data field can be used without modification.

If the transaction is sent to a contract account, a workaround will be needed as the data is also interpreted by the Ethereum VM. One approach for this would be appending the interchain transaction magic tag and routing information to original call data, as long as the contract logic does not rely on the CALLDATASIZE op code.

To ensure transaction finality, the bridge may require additional block confirmations; typically major exchanges use 120 (half an hour) for transaction confidence.

AION-1 BLOCKCHAIN

The Aion-1 blockchain is the genesis implementation of the connecting network. It is designed to be a fair, distributed, open blockchain architecture that is capable of fulfilling the requirements specified in the multi-tier blockchain network architecture. As an open blockchain, Aion-1 was designed with the following goals:

• Connecting blockchains and external services (e.g., oracles and databases) together through the contiguous network and providing accountable communication maintained through a decentralized network.

• Providing the necessary infrastructure to develop high-performance, decentralized, inter-blockchain applications.

• Creating a maintainable network through a robust and sustainable economic model.

Users will be able to deploy adjacent participating networks suitable for their own use cases and communicate with other networks through an accountable routing architecture.

Users ranging from large enterprises hosting consortium networks to community-oriented open networks are all welcome to participate. In the future, decentralized applications could sit on top of the connecting network with logic driven by integrating data from a multitude of blockchain networks.

In addition, the Aion-1 blockchain is equipped with a full-functioning economic system intended to drive the continued maintenance and integrity of the network.

Consensus

We first explore the consensus algorithm featured in Aion-1 to solve the requirements introduced by the connecting network concept. The consensus algorithm selected needs to maintain consensus of the blockchain for both on-chain transactions, and interchain transactions.

To fulfill these requirements in an efficient and immutable manner, Aion-1 uses a consensus algorithm based on a Byzantine Fault Tolerant

Defensive programming

Defensive programming will be supported by the Aion language. According to past research [10], mistakes made by chain-logic developers result from unexpected input data, runtime exceptions, and unexpected state change after reentrance. The Aion language will provide mechanisms to decrease the possibility of these common errors. The mechanisms include:

• Aion verifies the input data before passing it to a chain logic and validates the output data after the execution

• The scripting language introduces precondition, postcondition, and assertion to help programmers clearly organize their thoughts into a defensive pattern.

• Try/catch exceptions are fully supported by chain logic, emphasizing the handling of application state post exception rather than state rollbacks.

• Bounds of array access are checked at runtime.

Security

The security of the Aion language is derived from the defensive nature of the language and the AVM where time, space, and resource usage are strictly gauged and constrained.

Additionally, security should be emphasized through the tooling provided for the scripting language. For example, the logical correctness of Aion chain code can be provided by existing bytecode analysis, verification, and model checking tools.

Roadmap

Aion-1 will be rolled out in an iterative manner, starting from existing technologies and gradually moving towards the intended objectives. Aion-1 will be executed in three separate phases, with each phase focusing on different aspects of the technology and assembling the building blocks while progressing towards the finalization of the network (phase 3).

The exact deadlines for each phase and plans are subject to change as options for each phase are investigated more thoroughly.

The First Cross Blockchain Token

The AION token is initially being offered on the Ethereum blockchain as an ERC-20 token. As soon as the Aion network is operational, these ERC-20 tokens can be seamlessly converted to AION network tokens, and will continue to be able to flow freely back and forth between these two blockchains.

The Power and Utility of AION Token

The AION token is the fundamental method of interaction within the Aion network and its primary currency, powering:

AION-1 OPERATIONS

Mechanics of the Aion-1 blockchain are powered by the AION token, including the ability for users to stake tokens to back validators of Aion’s consensus process.

BLOCKCHAIN SOFTWARE APPLICATIONS

Developing applications on Aion-1 requires the use of AION tokens to access the resources of Aion Virtual Machine. Based on the complexity of the application, the AVM consumes tokens as fuel.

INTER-CHAIN BRIDGES

In order to instantiate a bridge from Aion-1 to any participating blockchain, AION tokens must be staked into a bridge registry contract. Once built, other nodes can join the bridge by also staking AION tokens. Fees for inter-chain transactions are set by bridges, and distributed to the validators on those bridges.

PARTICIPATING BLOCKCHAINS

AION tokens can be used to access and create customized Aion-compatible participating blockchains.

Conclusion

The team behind Aion has been particularly close to several large-scale enterprise projects, where the challenges outlined previously are significantly pronounced.

The Aion network is designed to overcome these challenges, and to propose a solution that will enable blockchain applications to achieve their full intended potential.

Team Member