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Overview

API utlizes blockchain and off-blockchain data storage. Blockchain side enables users to ensure the authenticity of information related to Aircrafts, in particular its' current ownership and all the historical transactions. In addition, not encrypted metadata regarding transactions, among others contents of all the formulars, are stored in a centralized database.

Stucture of the database intentionally doesn't make use of relations to enable easy switch to decentalized storage (such as BitTorrent network, StorJ, FileCoin etc.), in case it will be recommended in the future.

Blockchain contract storage

Fingerprints of all the fields from particular formulars are stored in Ethereum blockchain using smart contract writen in Solidity language. They are generated using SHA-224 cryptographic hash function, thus even a small change in the message will result in a mostly different hash, due to the avalanche effect. Example static content of contract stored in blockchain is presented below.

{
   "transferee_name":"1123c599095afde714bd13b6457c482f77fa64a4fe988e2b3eb57750",
   "transferee_address":"78d8045d684abd2eece923758f3cd781489df3a48e1278982466017f",
   "transferee_nationality":"076d364250f10e230a3a28b2a4175d7431b24bc290a8fe4f76f7c054",
   "transferor_name":"bd1a1bdf6eae5ee14c3fee371cca975a5e052009bc67ce8f11cb7271",
   "transferor_address":"78d8045d684abd2eece923758f3cd781489df3a48e1278982466017f",
   "transferor_nationality":"78d8045d684abd2eece923758f3cd781489df3a48e1278982466017f",
   "manufacturer_and_model":"78d8045d684abd2eece923758f3cd781489df3a48e1278982466017f",
   "manufactured":"86665612b0b232cb14f8605473d3a7e0d2f303ff7003c6f8916fdc4f",
   "last_maintenance":"0298f0bd0619d34fbe508628cef38adc827fcf4d93c700588f607adc",
   "serial_number":"83dd3a4315c03a802c7ab4bf6b61b2bd847976c1295e8e7284ec59b7",
   "registration_number":"4cfc3a1811fe40afa401b25ef7fa0379f1f7c1930a04f8755d678474",
   "transfered":"86665612b0b232cb14f8605473d3a7e0d2f303ff7003c6f8916fdc4f"
}

Data are stored in custom contract, in its only sttic field, as serialized JSON string (in order to make contract elastic, in sense no ingerention in solidity is required to store additional data – all the required changes can be done by performing quite standard changes in model and serializer).

It is possible to switch to ERC721 tokens with ease, but they seem to be a way too complex as it comes to the current needs.

Prerequirements and technology

API was developed in Python programing language, utilizing Django REST framework, as well as web3.py interface for interacting with the Ethereum blockchain and ecosystem. Apart from these and other python-related requirements (cf. requirements.txt file) two additional application have two be installed in target system, namely:

• the solc Solidity compiler (used to compile smart contract before they are signed and send),
• geth or equivalent interface for running a full ethereum node (since contract has to be signed using private key, for security purposes external services such as Infura do not provide this functionality).

After installing geth type geth account new in order to create an account that will be used for sending contract-related transactions to network. Account's keyfile and password should be provided in configuration file for proper system functioning (type geth account list to find out where is the relevant keystore file located).

Running, testing, API documentation

In order to install python requirements type pip install -r requirements.txt.

Make sure geth is running and all the required settings are provided in the configuration file. System can be tested eg. using Rinkeby Ethereum Testnet. In this case geth has to be run with an --rinkeby option.

Then type simply run server using python manage.py runserver command in the main project directory. It will be available at 127.0.0.1:8000 by default, where the detailed API documentation should appear.

Setup from scratch

Assuming you have ubuntu 18.04, run commands:

sudo apt update
sudo apt install python3-pip
sudo apt install build-essential libssl-dev
sudo apt install autoconf
sudo apt install libtool
sudo apt install libffi-dev
sudo apt install libgmp-dev
sudo apt install libsecp256k1-dev
sudo apt install pkg-config
sudo pip3 install -r requirements.txt

The last step - make sure that you are in the directory with code, and the requirements.txt is the right path.

After that run:

python manage.py migrate
python manage.py runserver 0:8080

This will run a development instance of your application.

Geth setup

Do a geth installation:

sudo add-apt-repository -y ppa:ethereum/ethereum
sudo apt-get update
sudo apt-get install ethereum
sudo apt-get install solc

Create a new geth account:

geth account new

Remember the password - it is the PASSWORD setting in settings.py You should also see something like this: 2ee833f885a517d557c204b78a2654f1e5020239

This is ACCOUNT setting in settings.py, but prepend '0x' to it, so:

ACCOUNT = '0x2ee833f885a517d557c204b78a2654f1e5020239'

Run:

geth account list

and pick a key file path from there:

keystore:///home/vagrant/.ethereum/keystore/UTC--2018-08-31T11-38-42.406701178Z--2ee833f885a517d557c204b78a2654f1e5020239

Then the KEYFILE setting in settings.py is:

/home/vagrant/.ethereum/keystore/UTC--2018-08-31T11-38-42.406701178Z--2ee833f885a517d557c204b78a2654f1e5020239

As metnioned earlier in the README - it is good to use test network for testing, this can be achieved by using --rinkeby attribute in the get run.

Also - in infura change api to rinkeby, eg.: rinkeby.infura.io/v3/909xxxxxxxxxxxxxxxxx

In the end your settings should look like this:

PRODUCTION

INFURA_URL = 'https://mainnet.infura.io/v3/909xxxxxxxxxxxxxxxxx' KEYFILE = '/home/vagrant/.ethereum/keystore/UTC--2018-08-31T11-38-42.406701178Z--2ee833f885a517d557c204b78a2654f1e5020239' PASSWORD = 'XXXXXXXXX' CHAIN_ID = 1 ACCOUNT = '0x2eexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'

TEST

INFURA_URL = 'https://rinkeby.infura.io/v3/909xxxxxxxxxxxxxxxxx' KEYFILE = '/home/vagrant/.ethereum/keystore/UTC--2018-08-31T11-38-42.406701178Z--2ee833f885a517d557c204b78a2654f1e5020239' PASSWORD = 'XXXXXXXXX' CHAIN_ID = 4 ACCOUNT = '0x2eexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'

with

geth --rinkeby

running.

As for CHAIN_ID:

0: Olympic, Ethereum public pre-release testnet
1: Frontier, Homestead, Metropolis, the Ethereum public main network
1: Classic, the (un)forked public Ethereum Classic main network, chain ID 61
1: Expanse, an alternative Ethereum implementation, chain ID 2
2: Morden, the public Ethereum testnet, now Ethereum Classic testnet
3: Ropsten, the public cross-client Ethereum testnet
4: Rinkeby, the public Geth PoA testnet
8: Ubiq, the public Gubiq main network with flux difficulty chain ID 8
42: Kovan, the public Parity PoA testnet
77: Sokol, the public POA Network testnet
99: Core, the public POA Network main network
7762959: Musicoin, the music blockchain
61717561: Aquachain, ASIC resistant chain
[Other]: Could indicate that your connected to a local development test network.

So in case of testing - you should have 4 set up, in case of production 1.

File Upload

1. Make sure you run the migrations:

   python3 manage.py migrate

2. Install paramiko (SSH connection handling):

   sudo -H pip3 install paramiko

File Upload is done in two steps:

• first you need to upload file under POST /files/
• in the response you will get the needed file_hash
• at this stage there will be an ssh connection triggered and the file metadata will reach the ubitquit.io servers
• you can use file_hash now in your contracts

3. Setup SSH credentials, as we do not want to store SSH credentials in the repository, do:

• create a file in the project root dir: ssh-credentials (touch ssh-credentials)

• place there a json with credentials (you can use nano editor -> nano ssh-credentials):

  {
      "username": "{username}",
      "password": "{password}"
  }
  

• ask Nathan or Sam for the credentials

4. After all of it is done - run:

   python manage.py runserver 0:8080