A cryptocurrency implementation in less than 1500 lines of code
A cryptocurrency implementation in less than 1500 lines of code
Cryptocurrencies and smart-contracts on top of a blockchain aren't the most trivial concepts to understand, things like wallets, addresses, block proof-of-work, transactions and their signatures, make more sense when they are in a broad context. Inspired by naivechain, this project is an attempt to provide as concise and simple an implementation of a cryptocurrency as possible.
From Wikipedia : A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange using cryptography to secure the transactions and to control the creation of additional units of the currency.
Naivechain uses websocket for p2p communication, but it was dropped to simplify the understanding of message exchange. It is relying only on REST communication.
Not all components in this implementation follow the complete list of requirements for a secure and scalable cryptocurrency. Inside the source-code, you can find comments with INFO: that describes what parts could be improved (and how) and what techniques were used to solve that specific challenge.
Provides an API to manage the blockchain, wallets, addresses, transaction creation, mining request and peer connectivity.
It's the starting point to interact with the naivecoin, and every node provides a swagger API to make this interaction easier. Available endpoints:
| Method | URL | Description |
|---|---|---|
| GET | /blockchain/blocks | Get all blocks |
| GET | /blockchain/blocks/{index} | Get block by index |
| GET | /blockchain/blocks/{hash} | Get block by hash |
| GET | /blockchain/blocks/latest | Get the latest block |
| PUT | /blockchain/blocks/latest | Update the latest block |
| GET | /blockchain/blocks/transactions/{transactionId} | Get a transaction from some block |
| GET | /blockchain/transactions | Get unconfirmed transactions |
| POST | /blockchain/transactions | Create a transaction |
| GET | /blockchain/transactions/unspent | Get unspent transactions |
| Method | URL | Description |
|---|---|---|
| GET | /operator/wallets | Get all wallets |
| POST | /operator/wallets | Create a wallet from a password |
| GET | /operator/wallets/{walletId} | Get wallet by id |
| GET | /operator/wallets/{walletId}/addresses | Get all addresses of a wallet |
| POST | /operator/wallets/{walletId}/transactions | Create a new transaction |
| POST | /operator/wallets/{walletId}/addresses | Create a new address |
| GET | /operator/{addressId}/balance | Get the balance of a given address |
| Method | URL | Description |
|---|---|---|
| GET | /node/peers | Get all peers connected to node |
| POST | /node/peers | Connects a new peer to node |
| GET | /node/transactions/{transactionId}/confirmations | Get how many confirmations a block has |
| Method | URL | Description |
|---|---|---|
| POST | /miner/mine | Mine a new block |
From the Swagger UI is possible to access a simple UI to visualize the blockchain and the unconfirmed transactions.
The blockchain holds two pieces of information, the block list (a linked list), and the transaction list (a hash map).
It's responsible for:
The blockchain is a linked list where the hash of the next block is calculated based on the hash of the previous block plus the data inside the block itself:
A block is added to the block list if:
…sh
$ node bin/naivecoin.js
$ node bin/naivecoin.js -p 3001 --name 1 $ node bin/naivecoin.js -p 3002 --name 2 --peers http://localhost:3001
http://localhost:3001/api-docs/
#### Example (wallet, address, transaction and mining)
```sh
# Create a wallet using password 't t t t t' (5 words)
$ curl -X POST --header 'Content-Type: application/json' -d '{ "password": "t t t t t" }' 'http://localhost:3001/operator/wallets'
{"id":"a2fb4d3f93ea3d4624243c03f507295c0c7cb5b78291a651e5575dcd03dfeeeb","addresses":[]}
# Create two addresses for the wallet created (replace walletId)
$ curl -X POST --header 'Content-Type: application/json' --header 'password: t t t t t' 'http://localhost:3001/operator/wallets/a2fb4d3f93ea3d4624243c03f507295c0c7cb5b78291a651e5575dcd03dfeeeb/addresses'
{"address":"e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"}
$ curl -X POST --header 'Content-Type: application/json' --header 'password: t t t t t' 'http://localhost:3001/operator/wallets/a2fb4d3f93ea3d4624243c03f507295c0c7cb5b78291a651e5575dcd03dfeeeb/addresses'
{"address":"c3c96504e432e35caa94c30034e70994663988ab80f94e4b526829c99958afa8"}
# Mine a block to the address 1 so we can have some coins
$ curl -X POST --header 'Content-Type: application/json' -d '{ "rewardAddress": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c" }' 'http://localhost:3001/miner/mine'
{
"index": 1,
"nonce": 1,
"previousHash": "c4e0b8df46ce5cb2bcb0379ab0840228536cf4cd489783532a7c9d199754d1ed",
"timestamp": 1493475731.692,
"transactions": [
{
"id": "ab872b412afe62a087f3a8c354a27377f5fda33d7c98a1db3b1b0985801a6784",
"hash": "423bae0bd2f4782f34c770df5be21f856b468a45bf88bb146da8ec2fe0fd3d21",
"type": "reward",
"data": {
"inputs": [],
"outputs": [
{
"amount": 5000000000,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
}
]
}
}
],
"hash": "0311a3a89198ccf888c76337cc190e2db238b67a7db0d5062aac97d14fb679b4"
}
# Create a transaction that transfer 1000000000 satoshis from address 1 to address 2
$ curl -X POST --header 'Content-Type: application/json' --header 'password: t t t t t' -d '{ "fromAddress": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c", "toAddress": "c3c96504e432e35caa94c30034e70994663988ab80f94e4b526829c99958afa8", "amount": 1000000000, "changeAddress": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c" }' 'http://localhost:3001/operator/wallets/a2fb4d3f93ea3d4624243c03f507295c0c7cb5b78291a651e5575dcd03dfeeeb/transactions'
{
"id": "c3c1e6fbff949042b065dc9e22d065a54ab826595fd8877d2be8ddb8cbb0e27f",
"hash": "3b5bbf698031e437787fe7b31f098e214a1eeff01fee9b95c22bccf20146982c",
"type": "regular",
"data": {
"inputs": [
{
"transaction": "ab872b412afe62a087f3a8c354a27377f5fda33d7c98a1db3b1b0985801a6784",
"index": "0",
"amount": 5000000000,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c",
"signature": "4500f432d6b400811d83364224ce62bccd042ad92299118c0672bc5bc1390ffdfdbef135f36927d8bd77843f3a0b868d9ed3a5346dcbeda6c06f33876cfae00d"
}
],
"outputs": [
{
"amount": 1000000000,
"address": "c3c96504e432e35caa94c30034e70994663988ab80f94e4b526829c99958afa8"
},
{
"amount": 3999999999,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
}
]
}
}
# Mine a new block containing that transaction
$ curl -X POST --header 'Content-Type: application/json' -d '{ "rewardAddress": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c" }' 'http://localhost:3001/miner/mine'
{
"index": 2,
"nonce": 6,
"previousHash": "0311a3a89198ccf888c76337cc190e2db238b67a7db0d5062aac97d14fb679b4",
"timestamp": 1493475953.226,
"transactions": [
{
"id": "c3c1e6fbff949042b065dc9e22d065a54ab826595fd8877d2be8ddb8cbb0e27f",
"hash": "3b5bbf698031e437787fe7b31f098e214a1eeff01fee9b95c22bccf20146982c",
"type": "regular",
"data": {
"inputs": [
{
"transaction": "ab872b412afe62a087f3a8c354a27377f5fda33d7c98a1db3b1b0985801a6784",
"index": "0",
"amount": 5000000000,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c",
"signature": "4500f432d6b400811d83364224ce62bccd042ad92299118c0672bc5bc1390ffdfdbef135f36927d8bd77843f3a0b868d9ed3a5346dcbeda6c06f33876cfae00d"
}
],
"outputs": [
{
"amount": 1000000000,
"address": "c3c96504e432e35caa94c30034e70994663988ab80f94e4b526829c99958afa8"
},
{
"amount": 3999999999,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
}
]
}
},
{
"id": "6b55b1e85369743f360edd5bedc3467eba81b35c2b88490686eee90946231dd6",
"hash": "86f5b4a40c027e1ef7e060dd9b9ab7ae48258f3a43dfc19d9d8111c396463b8c",
"type": "fee",
"data": {
"inputs": [],
"outputs": [
{
"amount": 1,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
}
]
}
},
{
"id": "0f6f6c04602ac1bea15157a1a86978d46488a7865fa3db3bfc581a1407950599",
"hash": "f9fa281fbf9ffd3d63dd0c3503588fe3010dd6740a4a960b98d1be4aa1fa7a05",
"type": "reward",
"data": {
"inputs": [],
"outputs": [
{
"amount": 5000000000,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
}
]
}
}
],
"hash": "08861fc4864ba0bf7a899db9ffaaa39376ad3857b1115951db074e3d06f93a5f"
}
# Check how many confirmations that transaction has.
$ curl -X GET --header 'Content-Type: application/json' 'http://localhost:3001/node/transactions/c3c1e6fbff949042b065dc9e22d065a54ab826595fd8877d2be8ddb8cbb0e27f/confirmations'
{"confirmations":1}
# Get address 1 balance
$ curl -X GET --header 'Content-Type: application/json' 'http://localhost:3001/operator/e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c/balance'
{"balance":9000000000}
# Get address 2 balance
$ curl -X GET --header 'Content-Type: application/json' 'http://localhost:3001/operator/c574de33acfd82f2146d2f45f37ce95b7bdca133b8ad310adbd46938c75992c8/balance'
{"balance":1000000000}
# Get unspent transactions for address 1
$ curl -X GET --header 'Content-Type: application/json' 'http://localhost:3001/blockchain/transactions/unspent?address=e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c'
[
{
"transaction": "c3c1e6fbff949042b065dc9e22d065a54ab826595fd8877d2be8ddb8cbb0e27f",
"index": "1",
"amount": 3999999999,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
},
{
"transaction": "6b55b1e85369743f360edd5bedc3467eba81b35c2b88490686eee90946231dd6",
"index": "0",
"amount": 1,
"address": "e155df3a1bac05f88321b73931b48b54ea4300be9d1225e0b62638f537e5544c"
},
{
"transaction": "0f6f6c04602ac1bea15157a1a86978d46488a7865fa3db3bfc581a1407950599",
"index": "0",
"amount": 5000000000,
"address": "e155df3No open issues yet, or sync has not completed.