Introduction to Ethereum Technology Architecture

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One 、Ethereum Overall framework

Ethereum The overall architecture includes the underlying services 、 Core layer 、 There are three layers of top-level applications .

• Underlying services ： Include P2P The Internet 、LevelDB、 Basic services such as cryptographic algorithms and sharding optimization ;
• Core layer ： Blockchain 、 Core components such as consensus algorithms and virtual machines ;
• Top level application ：API Interface 、 Smart contracts and decentralized applications （DApp）.
  

Two 、 block

So called blocks , In fact, it can be defined as a data structure that records transactions and status results that occur over a period of time , It is a consensus on the current ledger status .
block = Block head + Deal list + Uncle block , The block structure is shown in the figure below .

1、 Block head

Block head = Parent block hash value （Prev Hash） + Block hash value （Uncles Hash）+ Status tree root hash value （state Root）+ Transaction tree root hash value （Transaction Root）+ Receipt tree root hash value （Receipt Root）+ Time stamp （Timestamp）+ random number （Nonce）
Ethereum The important change of blockchain block data structure is Add three to the block Merkle Trees , State tree 、 Transaction tree and receipt tree .

* 2、 Deal list

The transaction list is a series of transactions in the revenue block selected by the miner from the transaction pool .

* 3、 Shu block

Blocks that are not on the main chain and are passed by the main chain Uncles The orphan block of the field contained in the blockchain is called “ Shu block ” .

3、 ... and 、 Account

The account is indexed by address , The address is derived from the public key （ After taking the public key 20 byte ）, Divided into external accounts （EOA） And the contract account , Both accounts are collectively referred to as “ State object ”（ Storage status ）, The external account stores the status of the etheric balance , Besides the balance, the contract account also has the status of smart contracts and their variables .
An account consists of four parts ：

• Number of transactions at this address （ Resist heavy defense attacks ）
• balance
• The binary code of the contract （ Only contract accounts have ）
• Account storage （ The default is empty. ）

1、 External accounts

• Created by the user , It can store ether currency , Controlled by public and private keys , Is the account actually controlled by the user .
• Three steps to generate an external account ：
  ① Set the account private key , Common user password ;
  ② Use encryption algorithm to generate corresponding public key from private key （secp256k1 Elliptic algorithm ）;
  ③ Get the address according to the public key （ After the public key 20 byte ）.
• The private key is the only basis for the user to control the account , Need to back up frequently .

* 2、 Contract account

• Created by an external account , Is the account that contains the contract code , Not directly controlled by the private key file , Controlled by contract code ;
• The address of the contract account is the address of the contract creator when the contract is created , And transactions sent from this address ;
• Ethereum All operations on the blockchain are performed according to the transactions sent by the account , When the contract account receives a transaction message , The contract code will be executed as the transaction input , It will also be executed by each node , And the execution results as part of the new block validation .

* 3、 Public and private keys

At present, there are three forms of private keys ：

• Private key： Randomly generated 256 Bit binary number ;
• Keystore & Password：Ethereum In the official wallet , Public and private key encryption is saved as JSON file , Store in keystore In the folder ;
• Memonic Code：BIP39 Put forward , Random generation 12~24 A word that is easy to remember , Create a random seed according to the function , And then generate a deterministic wallet in some way （Metamask Use ）.

* 4、 wallet

Wallet includes Mist、Parity and Etherwall Other types .

Four 、 Data structure and storage

1、 Data organization form

Ethereum Use Merkle Parircia Trie Trees （MPT）, Encrypted authentication data structure , The fusion Merkle Trees and Trie Trees are two data structures .

* 1.1 Merkle

• Tree data structure , But binary , Multi fork . Consists of a set of leaf nodes 、 A group of intermediate nodes and a root node ;
• The bottom leaf node contains basic data , Each intermediate node is a hash of its child nodes , The root node is a hash of its child nodes ;
• If there is malicious tampering and addition at the bottom of the tree , Will cause changes to the top and even the root of the tree .

* 1.2 Trie

• key It represents from the root to the corresponding value A real path ;
• If I have two value, They have the same prefix based key, The greater the proportion of the length of their same prefix , It represents these two value The closer you are in the tree , also Trie There will be no hash table like conflicts in the tree , One key Always correspond to one value.

* 1.3 MPT

• Ethereum be based on Merkle、Trie, Use MPT
• Each node is referenced by its hash value , be used for LevelDB Query in
• For storage in LevelDB Non leaf nodes in , Its representation in the database is ：key The RLP Coded SHA3 Hash value ,value It's nodal RLP code , namely k-v：Hash(RLP( node ))-RLP( node )

MPT 4 Types of nodes ：
① Blank nodes
② Leaf nodes ： A list of key value pairs ,key Is a special hexadecimal code ,value yes RLP code
③ Expansion nodes ： List of key value pairs , But here it is. value Is the hash value of other nodes , Connect to other nodes through this hash value
④ Branch nodes ： A length of 17 A list of . It can be the end of the search path , It can also be the intermediate node of the path

The following figure takes the state tree as an example

* 1.4 State tree

• Each node has 16 A child node , Each leaf node represents an account ;
• key Is the account address ,value Is the content of the account , Include 「nonce、balance、codeHash、storageRoot」.

* 1.5 The trading tree

• Each block has its own transaction tree ;
• key Is the transaction number ,value Is the content of the transaction .

* 1.6 The receipt tree

• Each block has a separate receipt tree , No need to update , Represents the corresponding receipt for each transaction ;
• key It's the index number , Used to guide the position of transactions related to this receipt ,value It is the contents of the receipt .

* 1.7 database LevelDB

Ethereum Three in total LevelDB database ：

• BlockDB： The main content of the block is the block header + transaction ;
• StateDB： Status data of the account ;
• ExtrasDB： Receipts and other supporting information .

5、 ... and 、 Consensus mechanism

1、Ethash

• boycott ASIC;
• Let miners get random data from blockchain status , Calculate some from the end of the blockchain N Randomly selected transactions in blocks , Returns its hash . In fact, it is from a search space generated according to historical information , Select the qualified hash value through hash calculation , So it is no longer a simple hash operation , You also need to have enough memory space ;
• The transition to PoS.

* 2、Casper

Based on the number and time of digital currencies held by network participants, the benefits are distributed , Introduce the concept of currency age , Valid address 51% The attack can reach the consensus of seconds , A block in a few seconds
Added a punishment mechanism , By paying a deposit , A good piece yields , Bad pieces lose the deposit .

6、 ... and 、 transaction

Transaction refers to the signature packet of a message sent from an external account to another account on the blockchain , Include the sender's signature 、 The address of the receiver and the amount of etheric money transferred by the sender to the receiver .

1、 transaction cost

• Prevent users from sending too many meaningless transactions in the public chain , Waste computing resources ;
• Gas It is the basic unit used to measure the computing resources consumed by a transaction ;
• Gas Price yes Gas The unit of , At present, it is relatively stable , But it can float freely according to the demand ,Gas Price*Gas The higher the , The faster the transaction is processed ;
• Gas Limit Indicates the maximum amount that the sender is willing to pay for the execution of this transaction Gas Number , Protect users from the impact of error codes, resulting in excessive transaction costs .

* 2、 Transaction content

The transaction can be a simple Ethereum transfer , It can also be a message containing smart contract code

It includes the following ：

• from
• to
• value
• data： Existing data fields , A delegate transaction is a transaction that creates or invokes a smart contract
• Gas Limit
• Gas Price
• nonce
• hash
• r、s、v： Three parts of transaction signature , The sender's private key pairs the transaction hash Make signature generation

* 3、 Type of transaction

• Transfer transaction ;
• Create transactions for smart contracts ;
• Execute transactions for smart contracts .

7、 ... and 、 Data encoding and compression

RLP Used to encode arbitrary binary data with nested structure , yes Ethereum Main method block of data serialization 、 Data structures such as transactions go through RLP Encoding processing , Then store it in the database .

8、 ... and 、API

• JSON-RPC API
• Web3.JavaScript API

Nine 、 Domain name service （ENS）

• Three main components ： The registry 、 Parser 、 Registration service ;
• Get the name through auction ;
• There will be no revenue , All funds are deposited or destroyed .