Table of Contents
As blockchain networks, Ethereum and Solana possess unique data structures, functioning as global public world computers that store and share data on their networks. In this chapter, we aim to explore how these chains structure their data sets.
'Account' in Ethereum
In Ethereum, an 'account' refers to an entity that owns Ether and can send transactions. It includes addresses necessary for deposits and withdrawals and is categorized as follows:
- EOA (Externally Owned Account): An account owned externally, possessing a private key. Think of it as an account for an individual's wallet.
- CA (Contract Account): An account for contracts, holding smart contract code.
A key difference between EOA and CA in Ethereum is that EOA, not being a smart contract, typically does not have its own storage. Therefore, the code hash of an EOA is set to a 'null' hash, indicating that the account does not have storage.
An Externally Owned Account (EOA) is an account with a private key, and possessing a private key means controlling access to funds or contracts. The private key implies control over access to funds or contracts.
The following data are included in an EOA:
| Field | Description |
address | An Account's address |
balance | The amount of ETH (in wei) an address owns. |
nonce | A counter that shows the number of transactions sent from the account to ensure transactions are processed only once. With smart contracts, it reflects the number of contracts created by the account. |
code hash | The code of an account on the EVM. |
storage hash (storage root) | A 256-bit hash of the root node of a Merkle Patricia Tree that encodes the storage contents of the account. This tree encodes the hash of the storage contents of this account, and is empty by default. |
A Contract Account contains smart contract code that simply cannot be held by an EOA. Additionally, a Contract Account does not have a private key. Instead, it is controlled by the logic of the smart contract code. This smart contract code, recorded on the Ethereum blockchain when the Contract Account is created, is a software program executed by the EVM.
Like an EOA, a Contract Account has an address and can send and receive Ether. However, when a transaction's destination is a Contract Account address, the transaction and transaction data are used as input for the contract to be executed in the EVM. In addition to Ether, the transaction can include data indicating a specific function of the contract to execute and parameters to pass to that function. Thus, a transaction can call functions within a contract. If requested by an EOA, contracts can also call other contracts. However, since a Contract Account does not have a private key, it cannot sign for transactions and cannot initiate transactions on its own. The relationships are summarized as follows:
- EOA -> EOA (OK)
- EOA -> CA (OK)
- EOA -> CA -> CA (OK)
- CA -> CA (Impossible)
'Account' in Solana
The concept of an Account in Solana is somewhat broader than in Ethereum. In Solana, all data is stored and executed based on Accounts. This means that in every case where state needs to be stored between transactions, it is saved using accounts. Similar to files in operating systems like Linux, accounts can store arbitrary data that persists beyond the lifespan of a program. Additionally, like a file, an account contains metadata that informs the runtime about who can access the data and how.
In Solana's Sealevel VM, all accounts are capable of storing data. So, where can smart contract developers store their data? They can store data in non-executable accounts (PDAs) owned by an executable account. Developers can create new accounts by assigning an owner identical to the address of their executable account to store data.
| Field | Description |
lamports | The number of lamports owned by this account. The equivalent of balance. |
owner | The program owner of this account. |
executable | Whether this account can process instructions. |
data | The raw data byte array stored by this account. |
rent_epoch | The next epoch that this account will owe rent. |
However, 'accounts' on the Solana network, which store data, require the payment of a fee. These accounts include metadata about the lifespan of the data they contain, represented in terms of a native token called 'Lamports'. Accounts are stored in validators' memory and pay 'Rent' to remain there. Validators periodically scan all accounts and collect rent. Accounts whose Lamports fall to zero are automatically deleted since they cannot pay for their rent. If an account contains a sufficient quantity of Lamports, it becomes exempt from rent, and no rent fees are deducted separately.
Solana's accounts are divided into the following two types, similar to Ethereum:
- Executable account (program account): These are smart contracts that store code, often referred to more simply as "programs".
- Non-executable account (data account): These can receive tokens or data but cannot execute code, as the executable variable is set to 'false'.
(*Unlike Ethereum, Solana uses the term 'Program' instead of 'Contract'.)
A comparison of the account structures in each chain reveals the following differences.
| Ethereum's Account | Solana's Account |
Account | owner |
balance | lamports |
nonce | [no equivalent] |
code hash | executable && data |
storage hash | data |
| [no equivalent] | rent_epoch |
| EOA (Externally Owned Account, Wallet) | -> non-executable, data accounts | However, individual wallets on Solana are composed of a collection of data accounts, which are a broader concept than EOA. |
| CA (Contract Account) | -> executable, program accounts | While sharing the same concept, Ethereum's CA cannot execute transactions on their own; they must be executed by EOA. |
Account abstraction
Ethereum has long been exploring the concept of account abstraction. There are two types of accounts in Ethereum: EOAs and CAs, each with distinctly different functions. Notably, contract accounts (CAs) cannot generate or sign transactions, leading to significant limitations. Transactions must be initiated and signed through an EOA, which implies the use of a base fee of 21,000 gas and adds to the complexity of account management. Account abstraction aims to eliminate these constraints, allowing a single account to perform the functions of both EOAs and contract accounts.
Consequently, the following adjustments can be made to the chart:
- EOA -> EOA (OK)
- EOA -> CA (OK)
- EOA -> CA -> CA (OK)
- EOA + CA (AA) -> CA (now, OK!)
For example, multisig wallets or smart contract wallets need to store a small amount of Ethereum in a separate EOA to pay for transaction fees, leading to the inconvenience of having to replenish it over time. Account abstraction allows a single account to execute contracts and issue transactions, improving this inconvenience.
Through ERC-4337, Vitalik proposed this concept to the community, and it was adopted in 2021, now implemented in the Ethereum network.
In summary, account abstraction offers the following benefits:
- Others paying my transaction fees, or me paying for others.
- Paying fees with ERC-20 tokens
- Setting custom security rules.
- Account recovery in case of key loss.
- Sharing account security among trusted devices or individuals.
- Batch transactions (e.g., authorizing and executing a swap in one go).
- More opportunities for dapp and wallet developers to innovate the user experience.
Is account abstraction implemented in Solana?
솔라나는 출시 이후부터 계정 추상화(AA)를 구현해 왔습니다. 앞서 논의한 바와 같이, 솔라나는 모든 데이터를 '계정'이라는 단위로 저장하며, 이는 실행 가능한 계정(program account)과 실행 불가능한 계정(데이터 계정)으로 나뉩니다. 솔라나는 처음부터 프로그램이 특정 계정을 생성하고 관리할 수 있는 기능(즉, 트랜잭션을 직접 시작하는 기능)을 지원했습니다. 솔라나에서 계정 추상화 기능을 확장하는 이 기능은 Program Derived Address(PDA)로 알려져 있습니다. 솔라나 프로그램은 데이터 계정과 달리 실행 가능한 코드를 포함하는 실행 가능 계정입니다. PDA를 통해 개발자는 트랜잭션 서명에 대한 규칙과 메커니즘을 설정할 수 있으며, 이를 통해 솔라나 네트워크에서 인식되고 승인된 제어 계정(PDA)을 대신하여 다양한 온체인 작업을 자율적으로 승인할 수 있습니다. 따라서 이더리움과 달리 솔라나는 번거로운 계층화 없이 솔라나 프로그램을 기반으로 다른 프로그램을 직접 제어할 수 있습니다.
Summary
- Solana's Account concept structures all data on the chain, with all data being based on Accounts.
- Solana natively supports AA, enabling self-calling between programs.
