Ethereum, smart contracts: you should know

History of emergence and motivation

With the advent of the concept of PoW in the bitcoin blockchain, secure decentralized exchange of tokens became possible. Each transaction goes through the following stages of verification, performed by some script:

• the amount of UTXO is unchanged (UTXO – Unspent transaction output in other words tokens)
• sender’s digital signature is valid Ethereum

To perform more complex transaction validation logic, you need to change the script, however, the Bitcoin platform provides an inconvenient, non-Turing complete language for writing such scripts.

Ethereum’s goal is to combine and improve the concepts of cryptocurrencies, altcoins and create an on-blockchain protocol that will allow developers to create distributed applications based on an infrastructure that provides scalability, Turing completeness, ease of development, and interoperability.

Accounts

The role of states on the air is performed by accounts. Each account has a 20-byte address. Changing the status of accounts occurs due to the transmission of messages Ethereum

Account fields:

• nonce– a counter that serves to ensure that each transaction is processed only 1 time
• ether balance— internal currency, used to pay for transactions
• contract code(if present)
• storage– data array, initially empty Ethereum

Account types:

Externally owned accounts– externally owned accounts do not contain executable code. The user can send a message from an externally owned account by signing the transaction

Contract accounts– when a message is received, the contract account is activated and executes the contract script code. The executable process can read and write from the internal storage, send messages, create other contracts

Messages

Ethereum messages are analogous to bitcoin transactions with three main differences:

1. An Ether message can be created by both an externally owned account and a contract account, while a bitcoin transaction can only be created by an externally owned account (user)
2. On-air messages explicitly support data transmission
3. The recipient of the message (if it is a contract account) has the option to return a response

Message Structure

• nonce
• GAS PRICE
• GAS LIMIT
• recipient
• Ether value
• Data
• sender’s signature: r,s,v (ECDSA)