A transaction refers to an action initiated by an account which changes the state of the blockchain. To effectively perform the state change, every transaction is broadcasted to the whole network. Any node can broadcast a request for a transaction to be executed on the blockchain state machine; after this happens, a validator will validate, execute the transaction and propagate the resulting state change to the rest of the network.

To process every transaction, computation resources on the network are consumed. Thus, the concept of "gas" arises as a reference to the computation required to process the transaction by a validator. Users have to pay a fee for this computation, all transactions require an associated fee. This fee is calculated based on the gas required to execute the transaction and the gas price.

Additionally, a transaction needs to be signed using the sender's private key. This proves that the transaction could only have come from the sender and was not sent fraudulently.

In a nutshell, the transaction lifecycle once a signed transaction is submitted to the network is the following:

  • A transaction hash is cryptographically generated.

  • The transaction is broadcasted to the network and added to a transaction pool consisting of all other pending network transactions.

  • A validator must pick your transaction and include it in a block in order to verify the transaction and consider it "successful".

For a more detailed explanation of the transaction lifecycle, see the Cosmos docs' corresponding section.

The transaction hash is a unique identifier and can be used to check transaction information, for example, the events emitted, if was successful or not.

Transactions can fail for various reasons. For example, the provided gas or fees may be insufficient. Also, the transaction validation may fail. Each transaction has specific conditions that must be fulfilled to be considered valid. A widespread validation is that the sender is the transaction signer. In such a case, if you send a transaction where the sender address is different than the signer's address, the transation will fail, even if the fees are sufficient.

Nowadays, transactions can not only perform state transitions on the chain in which are submitted, but also can execute transactions on another blockchains. Interchain transactions are possible through the Inter-Blockchain Communication protocol (IBC). Find a more detailed explanation on the section below.

Transaction Types

Neura supports two transaction types:

  1. Cosmos transactions

  2. Ethereum transactions

This is possible because Neura uses the Cosmos-SDK and implements the Ethereum Virtual Machine as a module. In this way, Neura provides the features and functionalities of Ethereum and Cosmos chains combined, and more.

Although most of the information included on both of these transaction types is similar, there are differences among them. An important difference, is that Cosmos transactions allow multiple messages on the same transaction. Conversely, Ethereum transactions don't have this possibility. To bring these two types together, Neura implements Ethereum transactions as a single sdk.Msg contained in an auth.StdTx. All relevant Ethereum transaction information is contained in this message. This includes the signature, gas, payload, etc.

Find more information about these two types on the following sections.

Cosmos Transactions

On Cosmos chains, transactions are comprised of metadata held in contexts and sdk.Msgs that trigger state changes within a module through the module's Protobuf Msg service.

When users want to interact with an application and make state changes (e.g. sending coins), they create transactions. Cosmos transactions can have multiple sdk.Msgs. Each of these must be signed using the private key associated with the appropriate account(s), before the transaction is broadcasted to the network.

A Cosmos transaction includes the following information:

  • Msgs: an array of msgs (sdk.Msg)

  • GasLimit: option chosen by the users for how to calculate how much gas they will need to pay

  • FeeAmount: max amount user is willing to pay in fees

  • TimeoutHeight: block height until which the transaction is valid

  • Signatures: array of signatures from all signers of the tx

  • Memo: a note or comment to send with the transaction

To submit a Cosmos transaction, users must use one of the provided clients.

Ethereum Transactions

Ethereum transactions refer to actions initiated by EOAs (externally-owned accounts, managed by humans), rather than internal smart contract calls. Ethereum transactions transform the state of the EVM and therefore must be broadcasted to the entire network.

Ethereum transactions also require a fee, known as gas. (EIP-1559) introduced the idea of a base fee, along with a priority fee which serves as an incentive for miners to include specific transactions in blocks.

There are several categories of Ethereum transactions:

  • regular transactions: transactions from one account to another

  • contract deployment transactions: transactions without a to address, where the contract code is sent in the data field

  • execution of a contract: transactions that interact with a deployed smart contract, where the to address is the smart contract address

An Ethereum transaction includes the following information:

  • recipient: receiving address

  • signature: sender's signature

  • nonce: counter of tx number from account

  • value: amount of ETH to transfer (in wei)

  • data: include arbitrary data. Used when deploying a smart contract or making a smart contract method call

  • gasLimit: max amount of gas to be consumed

  • maxPriorityFeePerGas: mas gas to be included as tip to validators

  • maxFeePerGas: max amount of gas to be paid for tx

For more information on Ethereum transactions and the transaction lifecycle, go here.

Neura supports the following Ethereum transactions.

:::tip Note: Unprotected legacy transactions are not supported by default. :::

Neura is capable of processing Ethereum transactions by wrapping them on a sdk.Msg. Neura achieves this by using the MsgEthereumTx. This message encapsulates an Ethereum transaction as an SDK message and contains the necessary transaction data fields.

One remark about the MsgEthereumTx is that it implements both the sdk.Msg and sdk.Tx interfaces (generally SDK messages only implement the former, while the latter is a group of messages bundled together). The reason of this, is because the MsgEthereumTx must not be included in a auth.StdTx (SDK's standard transaction type) as it performs gas and fee checks using the Ethereum logic from Geth instead of the Cosmos SDK checks done on the auth module AnteHandler.

Ethereum Tx Type

There are three types of transaction types used in Neura's Go Ethereum implementation that came from Ethereum Improvement Proposals (EIPs):

  1. LegacyTxType (EIP-155): The LegacyTxType represents the original transaction format that existed before Ethereum Improvement Proposal (EIP) 155. These transactions do not include a chain ID, which makes them vulnerable to replay attacks. EIP-155 was introduced to solve this problem by incorporating a chain ID, which uniquely identifies a specific Ethereum chain to prevent cross-chain replay attacks.

  2. AccessListTxType (EIP-2930): AccessListTxType was introduced with EIP-2930 as part of the Berlin upgrade. This new transaction type allows users to specify an access list – a list of addresses and storage keys that the transaction plans to access. The primary goal of access lists is to mitigate some of the gas cost increases introduced with EIP-2929, which increased gas costs for state access operations to improve denial-of-service (DoS) attack resistance. By specifying an access list, users can avoid paying higher gas costs for subsequent accesses to the same addresses and storage keys within the same transaction.

  3. DynamicFeeTxType (EIP-1559): DynamicFeeTxType was introduced with EIP-1559 as part of the London upgrade. This transaction type brought significant changes to Ethereum's fee market, with the aim of making gas fees more predictable and improving user experience. EIP-1559 transactions include two main components: a base fee and a priority fee (or tip). The base fee is algorithmically determined by the network, while the priority fee is set by users to incentivize miners to include their transaction. The base fee is burned, effectively reducing the overall ETH supply, while the priority fee goes to miners as a reward for their work. DynamicFeeTxType transactions allow for more predictable and efficient gas fee management.

These transaction types represent Ethereum's continuous evolution and improvements to its network, helping address challenges related to scalability, security, and user experience.

Interchain Transactions

Interchain transactions refer to the transfer of digital assets or data between two or more different blockchain networks.

Each blockchain network has its own unique protocol and data structure, making it difficult to directly transfer assets or data from one blockchain to another. Interchain transactions allow for the transfer of assets and data between different blockchains by using intermediary mechanisms or protocols.

One such mechanism is a cross-chain bridge, which acts as a connector between different blockchains, enabling the transfer of assets or data. Cross-chain bridges typically require some form of trust or consensus mechanism to ensure the security and integrity of the transaction.

Another possibility is to use the IBC (Inter-Blockchain Communication) protocol. To make an interchain transaction using IBC a user needs to:

  • Choose the source and destination blockchain networks that the user wants to transfer assets or data between.

  • Ensure that both blockchain networks have implemented the IBC protocol

  • Ensure there's a connection and channel established between the two blockchain networks using IBC

  • Initiate the transfer of assets or data: this is done by sending a transaction from the source blockchain to the destination blockchain through the IBC channel

Interchain transactions are becoming increasingly important as the number of different blockchain networks and applications continues to grow. They enable the interoperability of different blockchain networks, allowing for greater flexibility and efficiency in the transfer of digital assets and data.

Transaction Receipts

A transaction receipt shows data returned by an Ethereum client to represent the result of a particular transaction, including a hash of the transaction, its block number, the amount of gas used, and, in case of deployment of a smart contract, the address of the contract. Additionally, it includes custom information from the events emitted in the smart contract.

A receipt contains the following information:

  • transactionHash : hash of the transaction.

  • transactionIndex: integer of the transactions index position in the block.

  • blockHash: hash of the block where this transaction was in.

  • blockNumber: block number where this transaction was in.

  • from: address of the sender.

  • to: address of the receiver. null when its a contract creation transaction.

  • cumulativeGasUsed : The total amount of gas used when this transaction was executed in the block.

  • effectiveGasPrice : The sum of the base fee and tip paid per unit of gas.

  • gasUsed : The amount of gas used by this specific transaction alone.

  • contractAddress : The contract address created, if the transaction was a contract creation, otherwise null.

  • logs: Array of log objects, which this transaction generated.

  • logsBloom: Bloom filter for light clients to quickly retrieve related logs.

  • type: integer of the transaction type, 0x00 for legacy transactions, 0x01 for access list types, 0x02 for dynamic fees. It also returns either.

  • root : transaction stateroot (pre Byzantium)

  • status: either 1 (success) or 0 (failure)

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