# Transactions Transactions are cryptographically signed instructions from accounts. An account will initiate a transaction to update the state of the Electroneum network. The simplest transaction is transferring ETN from one account to another. ## Prerequisites To help you better understand this page, we recommend you first read [Accounts](https://developer.electroneum.com/foundational-topics/accounts) and our [Introduction to the Electroneum Smart Chain](https://developer.electroneum.com/foundational-topics/intro-to-the-electroneum-smart-chain). ## What's a transaction? An Electroneum transaction refers to an action initiated by an externally-owned account, in other words an account managed by a human, not a contract. For example, if Bob sends Alice 1 ETN, Bob's account must be debited and Alice's must be credited. This state-changing action takes place within a transaction.

Diagram adapted from Ethereum EVM illustrated↗

Transactions, which change the state of the EVM, need to be broadcast to the whole network. Any node can broadcast a request for a transaction to be executed on the EVM; after this happens, a validator will execute the transaction and propagate the resulting state change to the rest of the network. Transactions require a fee and must be included in a validated block. To make this overview simpler we'll cover gas fees and validation elsewhere. A submitted transaction includes the following information: * `from` – the address of the sender, that will be signing the transaction. This will be an externally-owned account as contract accounts cannot send transactions. * `recipient` – the receiving address (if an externally-owned account, the transaction will transfer value. If a contract account, the transaction will execute the contract code) * `signature` – the identifier of the sender. This is generated when the sender's private key signs the transaction and confirms the sender has authorized this transaction * `nonce` - a sequentially incrementing counter which indicates the transaction number from the account * `value` – amount of ETN to transfer from sender to recipient (denominated in WEI, where 1ETN equals 1e+18wei) * `input data` – optional field to include arbitrary data * `gasLimit` – the maximum amount of gas units that can be consumed by the transaction. The [EVM](https://developer.electroneum.com/foundational-topics/electroneum-virtual-machine-evm) specifies the units of gas required by each computational step * `maxPriorityFeePerGas` - the maximum price of the consumed gas to be included as a tip to the validator * `maxFeePerGas` - the maximum fee per unit of gas willing to be paid for the transaction (inclusive of `baseFeePerGas` and `maxPriorityFeePerGas`) Gas is a reference to the computation required to process the transaction by a validator. Users have to pay a fee for this computation. The `gasLimit`, and `maxPriorityFeePerGas` determine the maximum transaction fee paid to the validator. [More on Gas](https://developer.electroneum.com/foundational-topics/gas-and-fees). The transaction object will look a little like this: {% code lineNumbers="true" %} ```json { from: "0xEA674fdDe714fd979de3EdF0F56AA9716B898ec8", to: "0xac03bb73b6a9e108530aff4df5077c2b3d481e5a", gasLimit: "21000", maxFeePerGas: "300", maxPriorityFeePerGas: "10", nonce: "0", value: "10000000000" } ``` {% endcode %} But a transaction object 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. An Electroneum client like etn-sc will handle this signing process. Example [JSON-RPC](https://ethereum.org/en/developers/docs/apis/json-rpc/) call: {% code lineNumbers="true" %} ```json { "id": 2, "jsonrpc": "2.0", "method": "account_signTransaction", "params": [ { "from": "0x1923f626bb8dc025849e00f99c25fe2b2f7fb0db", "gas": "0x55555", "maxFeePerGas": "0x1234", "maxPriorityFeePerGas": "0x1234", "input": "0xabcd", "nonce": "0x0", "to": "0x07a565b7ed7d7a678680a4c162885bedbb695fe0", "value": "0x1234" } ] } ``` {% endcode %} Example response: {% code lineNumbers="true" %} ```json { "jsonrpc": "2.0", "id": 2, "result": { "raw": "0xf88380018203339407a565b7ed7d7a678680a4c162885bedbb695fe080a44401a6e4000000000000000000000000000000000000000000000000000000000000001226a0223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20ea02aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663", "tx": { "nonce": "0x0", "maxFeePerGas": "0x1234", "maxPriorityFeePerGas": "0x1234", "gas": "0x55555", "to": "0x07a565b7ed7d7a678680a4c162885bedbb695fe0", "value": "0x1234", "input": "0xabcd", "v": "0x26", "r": "0x223a7c9bcf5531c99be5ea7082183816eb20cfe0bbc322e97cc5c7f71ab8b20e", "s": "0x2aadee6b34b45bb15bc42d9c09de4a6754e7000908da72d48cc7704971491663", "hash": "0xeba2df809e7a612a0a0d444ccfa5c839624bdc00dd29e3340d46df3870f8a30e" } } } ``` {% endcode %} * the `raw` is the signed transaction in [Recursive Length Prefix (RLP)](https://developer.electroneum.com/advanced/data-structures-and-encoding/recursive-length-prefix-rlp) encoded form * the `tx` is the signed transaction in JSON form With the signature hash, the transaction can be cryptographically proven that it came from the sender and submitted to the network. ### The data field The vast majority of transactions access a contract from an externally-owned account. Most contracts are written in Solidity and interpret their data field in accordance with the [application binary interface (ABI)](https://ethereum.org/en/glossary/#abi). The first four bytes specify which function to call, using the hash of the function's name and arguments. The rest of the calldata is the arguments, [encoded as specified in the ABI specs↗](https://docs.soliditylang.org/en/latest/abi-spec.html#formal-specification-of-the-encoding). For example, lets look at [this transaction↗](https://etherscan.io/tx/0xd0dcbe007569fcfa1902dae0ab8b4e078efe42e231786312289b1eee5590f6a1). Use **Click to see More** to see the calldata. The function selector is `0xa9059cbb`. There are several [known functions with this signature↗](https://www.4byte.directory/signatures/?bytes4_signature=0xa9059cbb). In this case [the contract source code↗](https://etherscan.io/address/0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48#code) has been uploaded to Etherscan, so we know the function is `transfer(address,uint256)`. The rest of the data is: {% code lineNumbers="true" %} ``` 0000000000000000000000004f6742badb049791cd9a37ea913f2bac38d01279 000000000000000000000000000000000000000000000000000000003b0559f4 ``` {% endcode %} According to the ABI specifications, integer values (such as addresses, which are 20-byte integers) appear in the ABI as 32-byte words, padded with zeros in the front. So we know that the `to` address is [`4f6742badb049791cd9a37ea913f2bac38d01279`↗](https://etherscan.io/address/0x4f6742badb049791cd9a37ea913f2bac38d01279). The `value` is 0x3b0559f4 = 990206452. ## Types of transactions On Electroneum Smart Chain there are a few different types of transactions: * Regular transactions: a transaction from one account to another. * Contract deployment transactions: a transaction without a 'to' address, where the data field is used for the contract code. * Execution of a contract: a transaction that interacts with a deployed smart contract. In this case, 'to' address is the smart contract address. ### On gas As mentioned, transactions cost [gas](https://developer.electroneum.com/foundational-topics/gas-and-fees) to execute. Simple transfer transactions require 21000 units of Gas. So for Bob to send Alice 1 ETN at a `baseFeePerGas` of 190 gwei and `maxPriorityFeePerGas` of 10 gwei, Bob will need to pay the following fee:
{% code lineNumbers="true" %} ``` (190 + 10) * 21000 = 4,200,000 gwei --or-- 0.0042 ETH ``` {% endcode %} Bob's account will be debited **-1.0042 ETN** (1 ETN for Alice + 0.0042 ETN in gas fees) Alice's account will be credited **+1.0 ETN** The base fee will be burned **-0.00399 ETN** Validator keeps the tip **+0.000210 ETN** Gas is required for any smart contract interaction too.

Diagram adapted from Ethereum EVM illustrated↗

Any gas not used in a transaction is refunded to the user account. ## Transaction lifecycle Once the transaction has been submitted the following happens: 1. A transaction hash is cryptographically generated: `0x97d99bc7729211111a21b12c933c949d4f31684f1d6954ff477d0477538ff017` 2. The transaction is then broadcasted to the network and added to a transaction pool consisting of all other pending network transactions. 3. A validator must pick your transaction and include it in a block in order to verify the transaction and consider it "successful". 4. On Electroneum, the IBFT consensus mechanism provides 1-block finality for transactions, meaning that once your transaction is added into a block it is considered "final" and can never be changed or reversed. ## TYPED TRANSACTION ENVELOPE Ethereum originally had one format for transactions. Each transaction contained a nonce, gas price, gas limit, to address, value, data, v, r, and s. These fields are [RLP-encoded](https://developer.electroneum.com/advanced/data-structures-and-encoding/recursive-length-prefix-rlp), to look something like this: `RLP([nonce, gasPrice, gasLimit, to, value, data, v, r, s])` Ethereum has evolved to support multiple types of transactions to allow for new features such as access lists and [EIP-1559↗](https://eips.ethereum.org/EIPS/eip-1559) to be implemented without affecting legacy transaction formats. [EIP-2718↗](https://eips.ethereum.org/EIPS/eip-2718) is what allows for this behavior. Transactions are interpreted as: `TransactionType || TransactionPayload` Where the fields are defined as: * `TransactionType` - a number between 0 and 0x7f, for a total of 128 possible transaction types. * `TransactionPayload` - an arbitrary byte array defined by the transaction type. The Electroneum Smart Chain has introduced a new typed transaction in ETNIP-1, called Priority Transactions. This new transaction type follows the [EIP-2718](https://eips.ethereum.org/EIPS/eip-2718) envelope, where: * `TransactionType` = 0x40. * `TransactionPayload` = `RLP([nonce, gasPrice, gasLimit, to, value, data, v, r, s, priorityV, priorityR, priorityS])` ETNIP-1 transactions are prioritised by the validators. ## Further reading * [EIP-2718: Typed Transaction Envelope↗](https://eips.ethereum.org/EIPS/eip-2718) ## Related topics * [Accounts](https://developer.electroneum.com/foundational-topics/accounts) * [Electroneum Virtual Machine (EVM)](https://developer.electroneum.com/foundational-topics/electroneum-virtual-machine-evm) * [Gas and fees](https://developer.electroneum.com/foundational-topics/gas-and-fees)