A blockchain implementation in Python only for study.
The Blockchain-python implements simple blockchain and transactions. Currently, the implementation already has mining, transaction, communication between nodes, and file persistence of blocks and transactions.
The communication between nodes is via rpc based on http, rather than p2p network. Because the implementation of P2p is more complicated, it is too complicated to understand the framework of blockchain.
The verification based on cryptography has not yet been realized, and the verification of blocks between nodes and the verification of transactions have not yet been realized.
$ git clone https://github.com/Carlos-Zen/blockchain.git
$ cd blockchain$ python console account create$ python console miner start 3008$ python console tx transfer from_address to_address amount$ python console tx list$ python console blockchain listCopy the code resource to a new directory.While the miner before was running then:
$ cd {another_blockchain_directory}
$ python console node add 3008
$ python console node run 3009When a new block mined , block and transactions will broadcast to other nodes.
Use like this:
$ python console [module] [action] params...Such as:
$ python console tx list| Module | Action | Params | Desc |
|---|---|---|---|
| account | create | NONEED | Create new account |
| account | get | NONEED | Show all account |
| account | current | NONEED | The miner reward account |
| miner | start | ip:port/port | Such as 3008 or 127.0.0.1:3008 |
| node | run | ip:port/port | Such as 3008 or 127.0.0.1:3008 |
| node | list | NONEED | Show all node that will broadcast to |
| node | add | ip:port | Add a node that will broadcast to |
| tx | transfer | from_address to_address amount | Transfer coin from from_address to to_address |
| tx | list | NONEED | Show all transactions |
The blockchain is a data structure that is linked sequentially from back to forward by blocks containing transaction information. SHA256 cryptographic hashing is performed on each block header to generate a hash value. A bitcoin block is as follows:
{
"size":43560,
"version":2,
"previousblockhash":"00000000000000027e7ba6fe7bad39faf3b5a83daed765f05f7d1b71a1632249",
"merkleroot":"5e049f4030e0ab2debb92378f53c0a6e09548aea083f3ab25e1d94ea1155e29d",
"time":1388185038,
"difficulty":1180923195.25802612,
"nonce":4215469401,
"tx":["257e7497fb8bc68421eb2c7b699dbab234831600e7352f0d9e6522c7cf3f6c77",
#[...many more transactions omitted...]
"05cfd38f6ae6aa83674cc99e4d75a1458c165b7ab84725eda41d018a09176634"
]
}A blockchain is a linked list structure of blocks. The essence of mining is a new block, based on existing information such as parent block hash, timestamp, transaction merkle hash, plus a nonce (number from 0)
A sha256 representation string is generated after the connection. If the preceding digits start with several zeroes, the number of zeros is the difficulty of mining, and half is dynamically adjusted based on the remaining number and the generation speed of the previous block, such as:
00000000000000027e7ba6fe7bad39faf3b5a83daed765f05f7d1b71a1632249Successful mining, block generation
Blockchain-python simplified block structure, a blockchain-python block data is as follows:
{
"index": 7,
"timestamp": 1528972070,
"tx": [
"b959b3d2099ca304c67087edbf05b79d1f2501b1f407df5e51a1a8c22bb3334d",
"613e4af7266e01ea338d30681ef606bad26e4cdfa4ec7a6f431e22420c8291fd",
"be7095a764cb241606a67c9064bc8dbc2da2370d49459bd492473ea5ce304cb3"
],
"previous_block": "00003e17e04d9c9d2c2f5629de20bda58f59af36417a7e50eb77a74a028b026a",
"nouce": 11063,
"hash": "00006805c75d0db1685616d9ea5730f6203eda744a16fcc78ef1f3c244083ea4"
}The calculation of block hash is roughly the same as that of Bitcoin. Our difficulty setting is relatively low, so the hash in front of this block has only 4 zeros.
This is for easier mining to understand the principle and generally can be produced in a few seconds. One block. In addition, Bitcoin's tx field represents the root node hash of the merkle tree that consists of the transaction hash.
For simplicity, we put it directly into the array of transaction hash.
The sha256 used by the mining algorithm, Bitcoin's algorithm is based on the block header +Nouce (a number) as a string. Simple blockchain simplifies the header information, but the mechanism and Bitcoin are constant. The blockchain is stored locally in the file in json format. The generation of a block is related to the transaction information, so the block information is also stored when the block is stored. There will be rewards for mining, and the reward will be recorded as the first transaction in the blockchain.
We simplified the implementation and only implemented rewards. The reward will be awarded to the current account. If the current account does not exist, please generate an account through the following command line:
$ python console account createThe blockchain network is a P2P (Peer-to-Peer, end-to-end) network. We use Python's own RPC mechanism for simplification.
Bitcoin uses the UTXO model and does not directly exist in the concept of “balance”. The balance needs to be obtained by traversing the entire transaction history. We also implement this mechanism. A transaction is a combination of some input and output. In our transaction, we accept multiple inputs and generate multiple outputs.
The correctness check of the transaction is under development.
Contributions are welcome! Please feel free to submit a Pull Request.