Gli account su Solana funzionano in modo diverso da Ethereum
Account su Ethereum
Il modello di account di Ethereum
- 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 su 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. |
Accounts that store data pay for the space they use. Every account holds a balance in lamports (the smallest unit of SOL) and must keep a minimum balance proportional to its data size, known as the rent-exempt threshold. Ongoing rent collection is disabled on Solana, so this minimum works as a refundable deposit rather than a recurring fee: you deposit it when you create the account and get it back when you close the account. An account whose balance drops to zero is removed from the ledger.
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.
| 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
Introduzione all'account abstraction
Confronto
- 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.
Vitalik Buterin and others proposed ERC-4337 in 2021, and its EntryPoint contract went live on Ethereum mainnet in March 2023.
Vantaggi
- 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.
Account Abstraction su Solana
Solana ha implementato l'Account Abstraction (AA) sin dal suo lancio. Come discusso in precedenza, Solana memorizza tutti i dati in unità chiamate 'account', suddivise in eseguibili (program account) e non eseguibili (account di dati). Fin dall'inizio, Solana ha supportato la capacità per i programmi di creare e gestire account specifici (ovvero avviare direttamente transazioni). Questa funzionalità, che estende le capacità di astrazione degli account in Solana, è nota come Program Derived Address (PDA). I programmi Solana, a differenza degli account di dati, sono account eseguibili contenenti codice eseguibile. Con i PDA, gli sviluppatori possono impostare regole e meccanismi per le firme delle transazioni, permettendo a varie azioni onchain di essere autonomamente autorizzate per conto di un account controllato (PDA) riconosciuto e approvato dalla rete Solana. Pertanto, a differenza di Ethereum, Solana consente il controllo diretto di un altro programma basato su un programma Solana senza una stratificazione complessa.
Riepilogo
- Solana's Account concept structures all data on the chain, with all data being based on Accounts.
- Solana covers the goals of account abstraction natively: any account can pay fees, transactions carry several instructions and signers, and programs sign for PDAs through cross-program invocation.