---
layout: simple
---
## A toy chain

### The chain should have these properties:

   - Running on at least 2 pre-defined [nodes][7] (IP addresses given in a [config file][8] / no additional discovery necessary)-
   - [PoW][9], with every node a miner-
   - The [difficulty][10] is fixed (i.e., block time is not), each [block rewards][12] 100 coins-
   - [ECDSA][13] cryptography; addresses may be pure public keys-
   - Protect against [double][14] spending
   - [Transactions][11] can have additional data payload, signed by the sender (and there needs to be a way to [set it][5])
   - Blocks can have additional data payload (and there needs to be a way to set it)
   - Implement a simple REST-like [web service][1] [API](/api/) which implements the following services and returns JSON data:
     * Query the [block count][2].
     * Query a [single block][3] and return all its transaction data.
     * Query a [single transaction][4] and return all its data.
     * Create a [transaction][5] from JSON [data][11] and accept it for [mining][6].

### Example of curl commands

   ```sh
   # getting block count
   curl http://127.0.0.1:8089/api/0.0/getheight
   # getting 4th block
   curl http://127.0.0.1:8089/api/0.0/getblock?n=4
   # getting transaction Ztxrms5c5oKqb9Zof3xeC5Q2ZQjSaWv7FU4rAxe2s3sP
   curl http://127.0.0.1:8089/api/0.0/gettx?txaddr=Ztxrms5c5oKqb9Zof3xeC5Q2ZQjSaWv7FU4rAxe2s3sP
   # posting a transaction
   cat txpool/tx.yml | sed -e "s/$/%0a/g" | curl -s -X POST http://127.0.0.1:8089/api/0.0/settx -d @-
   # processing the txpool (mining)
   curl http://127.0.0.1:8089/api/0.0/minepool
   
   ```

### Security Warning

 Blockchains are transparent and public so we encrypt private keys and other sensitive data,
 however as it is just a toy, we expose **all the files** for educational purpose.

>> ** PLEASE DO NOT USE IN A PRODUCTION ENVIRONMENT **

 note:
   sensitive data are encrypted w/ git-crypt;
   please send us your public key if you need access
   or ask for a shared DH secret

   decrypt can be done with the command :

   ```sh
   export GPG_ASKPASS=ssh-askpass
   git-crypt unlock
   #gpg --decrypt local.key.asc | git-crypt unlock -

   ```


[1]: webservice.html
[2]: http://127.0.0.1:8089/api/0.0/getheight
[3]: http://127.0.0.1:8089/api/0.0/getblock
[4]: http://127.0.0.1:8089/api/0.0/gettx?encode=json&addr=txcoin
[5]: http://127.0.0.1:8089/api/settx.html
[6]: http://127.0.0.1:8089/api/0.0/minepool
[7]: http://127.0.0.1:8089/docs/nodes.html
[7a]: http://127.0.0.1:8089/api/0.0/getnodes
[8]: http://127.0.0.1:8089/api/0.0/config
[9]: http://127.0.0.1:8089/docs/pow.html
[10]: http://127.0.0.1:8089/docs/difficulties.html
[11]: http://127.0.0.1:8089/api/transaction.html
[12]: http://127.0.0.1:8089/docs/bkreward.html
[13]: http://127.0.0.1:8089/admin/keygen.html
[14]: http://127.0.0.1:8089/docs/UTXO.html