As we pointed out in part I of this series, the days when hardware and software were separate entities are long gone. Along with the ongoing worldwide digitization and digitalization, the integration between the virtual and physical worlds is getting stronger – making the Internet of Things (IoT) a real thing. Going further, we can leverage blockchain features like data immutability, distributed character, and exploit the smart contracts it offers to connect it with IoT applications to build a trusted and all-inclusive solution. We’ve created a two-part tutorial to showcase how to deploy and connect all the pieces. In part I of our tutorial, we set up a private Hyperledger Besu network and configured a Raspberry Pi to sign transactions with its own keys. We used this to write a Python program, hosted on Raspberry, sending Ether to other participants of the network. The final solution used quite a broad technological stack: Terraform, Amazon Web Services, MetaMask, and, finally, Raspberry Pi. In part II, we don’t want to lower the bar, so here we add some extra technological stack on the top of what we had.
Scenario
Let us consider a contract between a supplier and a buyer. They both agree on some delivery time, conditions, pick up and drop off locations, and, of course, the price the buyer is willing to pay. Among the conditions, they can agree on some penalty for delayed delivery or that the parcel couldn’t be exposed to a temperature higher than some threshold longer than X minutes. While the delivery time can be verified, the monitoring of the second condition is not that easy to verify. Even if we suspect that the temperature threshold has been exceeded (because, for example, the delivered food is spoiled), how can we prove that transport conditions were inappropriate?
In part II, Ratified Smart Contract for Constrained Delivery with Oraclized Data, we created an automated solution covering the entire supply process, including:
- publishing the delivery offer with specified conditions,
- acceptance of the conditions by contractor,
- starting the delivery by an authorized person (using personalized hardware signature),
- monitoring the delivery temperature and contract voiding conditions, confirming the delivery, and
- calculating the final payment for the supplier.
To achieve this, we take advantage of the Hyperledger Besu network that was deployed in part I and now write a smart contract on the top of it that handles the delivery operations.
Overview
In the full tutorial, we detail all the steps to designing a smart contract for the presented delivery use case. To do this, we use web-based Remix IDE as an environment for contract development while the contract itself is written in the Vyper language. We opted for this pythonic language for the simplicity and readability of its code. Once the contract is developed, we show how to test the deployment to verify that all the functionalities are working correctly.
Further, we go through the steps required to use the hardware signature (contained in the smart card) to sign the transaction, to configure the temperature sensor and measure the current value of the temperature, and, finally, to integrate all the parts into one program that will serve as “delivery starter” and “temperature measurement provider.”
Our tutorial covers a very concrete use case, and it is only the tip of the iceberg. There’s much more, and the possibilities are endless. We hope that this tutorial will give you the thrill to build your own blockchain application. If you have any questions, feel free to contact us!