Building a Blockchain Application with Simplicity

Introduction

Blockchain has come a long way from being a niche concept to a game-changer reshaping industries across the globe and its impossible to ignore its impact!!!

Blockchain technology and its distributed ledger have revolutionized the transactions allowing consumers to have in a trustless manner where there is no central authority. Blockchain has different principles to safeguard the currencies like public and primary keys, digital signatures, and consensus mechanisms.

So, with all the buzz around blockchain development, let’s take a step back and understand – what exactly is blockchain?

Blockchain is the link of blocks where the blocks have data and information about the transactions this is a distributed ledger with security as the vital.

In this article, we’ll walk you through every step of building your own blockchain application using the Simplicity programming language.

Simplicity in Blockchain:

Let’s have a look at this new programming language.

Simplicity is the new programming language in the blockchain domain specially designed for smart contracts. Simplicity is the solution to the existing issues in languages like Bitcoin script and Ethereum’s EVM. Simplicity is a combinator-based and typed language.

What is a typed language?

A typed language follows rules about the types of values you can use in different operations. In simpler terms, every element, like a variable, expression, or function, has a specific type, and the system ensures that the types used together are compatible.

What is a combinator-based language?

A combinator-based language uses small, predefined operators (combinators) to perform calculations by combining different elements and producing a result.

How Is Simplicity Different from Regular Programming Languages?

Most programming languages focus mainly on how the code runs (operational semantics). Simplicity, however, combines both how the code runs and its mathematical meaning (denotational semantics). Let’s break this down further.

Denotational Semantics in Simplicity

Simplicity has formal rules for its meaning, defined using a tool called Coq. Denotational semantics looks at the mathematical meaning behind the language instead of just how the code executes. Coq helps provide formal proofs in both math and computer science to define Simplicity’s behavior.

Operational Semantics in Simplicity

Simplicity also includes operational semantics, defined using a tool called Bit Machine. Bit Machine measures the computational space, time, and resources needed to run Simplicity programs.

Put simply, Simplicity is built on solid mathematical rules, giving it predictable behavior beyond just running code. When you write in Simplicity, there is a logical foundation behind every line, making it highly reliable for blockchain applications.

Why Choose Simplicity?

• Expressive Language: Offers the tools needed to create smart contracts.
• Static Analysis: Helps determine upper bounds and computational complexities.
• Efficient Use of Resources: Reduces bandwidth and storage requirements.
• Enhanced Privacy: Improves user privacy by removing unused code.
• Secure Design: Maintains Bitcoin’s design principles to safeguard information.
• Formal Semantics: Makes reasoning about code easier.

Setting Up the Development Environment

This step is the foundation of all the development. We know it’s very mundane to do all of it manually but follow the guide below and you are good to go!

Installing Simplicity

• Go to the official repository and download the latest version of Simplicity or
• git clone https://github.com/ElementsProject/simplicity.git
• cd simplicity (you need to type this in your terminal)
• Install dependencies: sudo apt-get install build-essential libtool autoconf 
• Install Simplicity based on the instructions and compatible version to your system and Build.Type the below-given commands in the cmd prompt or terminal:
  • ./autogen.sh
  • ./configure
  • make
  • sudo make install
• Verify installation using:
  simplicity –version

Congratulations!! You have successfully downloaded and setup the programming language.
Choosing an IDE

Choosing an IDE

This is a very important step, as choosing a proper IDE without any configuration discrepancies is the base of all your future projects.

Visual Studio Code: VScode is a free and open-source platform developed by Microsoft. VsCode is the evergreen IDE and most preferred by coders due to its IntelliSense i.e. completing the code and having code recommendations.

• Install and set up extensions for Simplicity:
  • Go to the official website of Vscode
  • Download the installer and follow the instructions in the prompt
  • Open Vscode and navigate to Extensions in the Activity Bar or use the shortcut: Ctrl+Shift+X
  • Then set extensions like
    • Simplicity- for the language
    • IntelliSense-to complete the code and have recommendations
    • Code Runner- to run the code snippets easily
    • Git Lens- for seamless git experience

Simplicity CLI: Simplicity CLI is essential for development tasks like compiling and running Simplicity code.

• Open the terminal or command prompt
• Use a package manager like brew, npm, or apt-get(depending on your OS) and install the SImplicity CLI.
  • For macOS/Linux: brew install simplicity-cli
  • For Windows: npm install -g simplicity-cli
• You can also visit the official CLI repository and follow the instructions provided in the readme

Installing Required Libraries

For Installing the required libraries you will need to use package managers to simplify the process.

If Simplicity has a package manager then use it like: simplicity install

Understanding Blockchain Concepts with Simplicity

Enough with the coding for now! Let’s dive into the core concepts and structure that make blockchain tick.

Blockchain Basics in Simplicity

Blockchain has three basic components Blocks, transactions, and Chains. In this section, we will understand the structure in detail.

• Blocks: Blocks are the basic and primitive cells of this blockchain ecosystem. This is a basic unit that stores a list of particular transactions. Blocks can be created or widely we can say mined using various consensus mechanisms. Each block will have its own set of identifiers which presumably need to be unique called a hash.
• Transaction: Transactions are the transport of data, values, or currencies within the blockchain network along various nodes.  Transaction details are stored in a block in unison with some set of protocols.
• Chains: Blockchain can be compared to a linked list in data structure terms. Just as linked list elements are connected through links, blockchain blocks are connected through hashes. Chains ensure data integrity and security by linking each block with the hash of the previous block.

Key Features of Blockchain: Decentralization, Immutability, and Consensus Mechanisms

• Decentralization: No single entity controls the blockchain database, reducing the risk of system failure or bias. Each participant (node) maintains a copy of the blockchain, ensuring transparency.
• Immutability: Data entered into the blockchain cannot be changed without altering all subsequent blocks, thanks to cryptographic hashing.
• Consensus Mechanism: Protocols that ensure all nodes in the network agree on transactions and maintain a consistent state. This is crucial for the security and integrity of the blockchain.

 All the above attributes are necessary for blockchain as it is the core of the security and integrity principles of blockchain.

Components of a Blockchain Application

Block structure:

• Index: An index is an integer representing the position of the block within the blockchain. Indexing helps in identifying the order of the blockchain. The Genesis block has an index of 0.
• Timestamp: The time stamp stores the instance at which the block was created in the form of a string. This helps in maintaining the record of the block like when the block was mined or added to the blockchain. The main purpose is to maintain the chronological order of the blocks and transactions.
• Transactions:  These are represented as vectors of Transaction objects, where each Transaction represents a transfer of data or value between participants.Stores all transactions included in the block. Transactions are the core data of the blockchain, and each block contains a batch of transactions that need to be processed and verified.
• Previous hash and Hash: Previous hash stores the cryptographic hash of the previous block whereas the hash is a string of cryptographic information but in a jumbled way.

Creating and verifying transactions: 

 In simple terms, a transaction is just an exchange of data between two parties. 

For a transaction to happen, we need a few basic details: the sender, the recipient, and the value or data being transferred. Before a transaction gets added to a block on the blockchain, it must first be verified to ensure it has the correct digital signature and passes several security checks. Once it’s authenticated, the transaction is grouped into a block and then added to the blockchain.

Building a Simple Blockchain with Simplicity

Let’s start with the practical implementation of the blocks and their attributes and methods using Simplicity.

Creating the Block Class

As we have studied in the earlier section about the structure of a block let’s put it into the practical domain:

In the above code snippet we have defined:

• Index of the block that represents the position
• The timestamp that records the time when the block was created
• Data that has all the transaction information
• A previous hash that stores hash of the proceeding block
• Hash which is a unique identifier also known as cryptographic hash function

Also the method calculate_hash takes the input and appends its content and applies the sha256 hashing to generate the block’s hash.

Creating the Blockchain Class

As we are done with defining the basic block structure further we need to define block classes and methods to create new blocks:

n the above code snippet:

• Genesis Block is the first blockchain and has an index of 0. Genesis block is the foundation of all the other blocks
• Get Latest block fetches the most recent block- this method is necessary to add new blocks
• Add block appends the new block to the blockchain it calculates the previous hash and the hash of the current block.

Implementing Consensus Mechanisms in Simplicity

Consensus algorithms are the rules that participants in a blockchain network follow to agree on which blocks get added and how new ones are created. Here are some common mechanisms:

• Proof of Stake: Validators are selected based on the highest number of coins they possess and the stake they are willing to offer in exchange of adding or validating a new block.
• Proof of Work: In this mechanism, the miners need to solve a cryptographic problem or puzzle and they compete on the parameters of time, the first one to solve it gets to add the new block.
• Others: There are also other algorithms like Delegated Proof of Stake (DPoS), where network participants vote for delegates who validate transactions, and Practical Byzantine Fault Tolerance (PBFT), designed to function even if some participants act maliciously or fail.

Proof of Work

Proof of Work (PoW) is one of the most well-known consensus mechanisms in the blockchain world. It’s a protocol designed to protect the integrity of the data, validate new blocks, and ensure they’re securely added to the chain.

In simple terms, miners compete to solve a complex cryptographic puzzle, and the first one to crack it gets the honor of adding the next block to the blockchain. It’s like a race – whoever solves it first wins the prize!

This puzzle is nothing but a mathematical problem of finding out the perfect nonce and hash and validating it fastest. While you solve the problem you need to generate the hash in a unique combination, then check the hash for the difficulty level and repeat until you find the perfect match.

Add proof attribute and proof_of_work method in Block class using Simplicity syntax.

In the above code snippet:

• We have added the proof attribute to store the nonce value for PoW
• In the second part, we have implemented the proof of work by 
• Initializing the nonce and incrementing it with each iteration
• Calculate the hash of the current block
• Keep a check on the difficulty of the block method and if it fits into the criteria
• Keep on iterating till you find out the correct nonce.
• validate the proof by checking if the hash meets the difficulty criteria and return the result

Update the Blockchain class to validate proof before adding new blocks.

• In the above code snippet add_block method is updated to include a proof validation step before adding the block to the blockchain.
• The if else condition checks for the validation and then the block is added.

Creating a Simple Blockchain API with Simplicity

Once you are done with the basic functionalities of the block you can move to the API creation since it will serve as the interface for the users and will allow the new users to add and view the blocks and their states and attributes.

Setting Up the API Environment

Install and configure tools required for creating APIs with Simplicity:

• Firstly you need to have the frameworks hence install the HTTP server libraries as shown in the code above
• Now set up the environment and configure the server to handle all the incoming requests.
• Once you are done with the setup test the environment to ensure your server is running seamlessly

Building the API

Create an API to define endpoints for adding blocks and viewing the blockchain using Simplicity.

Let’s start building our API now:

• ./add_block: POST this request to add a new block 
• ./get_chain: GET requests to fetch the current state of the block
• The /add_block endpoint will accept a JSON payload containing the data for the new block and will add this block to the blockchain.
• In the second part, we perform the request casing with the add block handler
• Adding the new blocks and recalculating the hashes
• Fetching the responses on the server

• Once you are done with building the API set up the routes for server configuration:
• The /add_block and /get_chain are used to add routes
• Now start the server and keep a check on the incoming requests.

Running and Testing the Application

Congratulations! You’ve reached the final module, where you can run your server and interact with the blockchain using APIs. Now, it’s time to test your setup – try sending transactions, retrieving data, and confirming that everything is working as expected. Don’t forget to check for errors and edge cases to ensure your blockchain application runs smoothly!

Running the Application

• Compile the program and run the Simplicity blockchain application:
• ./start-server  # Command to start your server

Testing with Postman

• Install Postman
• Launch postman
• Test the endpoints:
• curl -X POST -H “Content-Type: application/json” -d ‘{“data”: “New block data”}’ http://localhost:PORT/add_block

After this command should output the updated blockchain data, indicating the successful addition of the block.

•  Adding a block and viewing the blockchain using the API created with Simplicity:
• curl -X POST -H “Content-Type: application/json” -d ‘{“data”: “Example data for a new block”}’ http://localhost:PORT/add_block

 Live Example of Building a Blockchain Application with Simplicity

Step-by-Step Execution

• Step 1: Create a Block class with its key attributes (like index, timestamp, data, and previous hash).
• Step 2: Implement a method to calculate the hash for each block, ensuring its uniqueness.
• Step 3: Define a Blockchain class and initialize it with the very first block, known as the genesis block.
• Step 4: Add methods to the Blockchain class to add new blocks and fetch the latest block, using Simplicity.
• Step 5: Introduce the Proof of Work mechanism to the Block class and update the Blockchain class accordingly.
• Step 6: Set up an API environment to handle incoming requests using Simplicity.
• Step 7: Test your application by mining a new block and validating the blockchain through tools like Postman or curl.

This code snippet serves as a comprehensive guide all in one place. Feel free to experiment with it and build new applications on your own.