What is a Blockchain?
A blockchain is a system that records information in a very secure, transparent way, and above all that cannot be modified once registered. Each group of information, called a "block," contains transactions, and each block is linked to the previous block, forming a strong chain — hence the name "blockchain."
This technology allows digital currencies like Bitcoin to operate without the need for a central authority, i.e., without a single bank, government, or company controlling everything. Instead, it's a network of computers around the world that makes sure everything is correct and that no one is cheating.
In blockchain systems, each block contains a cryptographic hash of the previous block, along with its own list of transactions and its own hash. This creates a secure, tamper-evident chain.
How Parallel Chains of Hashes Help Validate Blocks & Prevent Double Spending:
Each block's hash depends on both its own data and the hash of the previous block. This means if someone tries to change a past transaction, the hashes of all following blocks would no longer match, making the tampering obvious.
In blockchain networks like Bitcoin, there isn't just one copy of the blockchain. Thousands of computers (called nodes or miners) maintain independent, parallel copies of the chain. They constantly check and compare hashes across the network.
When a new block is created, all nodes validate it. They check:
- The block's hash is correct.
- All transactions in the block follow the rules (for example, no double spending).
Double spending means trying to use the same digital coin in two places. The blockchain prevents this because:
- Every transaction is recorded in a block and broadcast to the entire network.
- Once included in a block and confirmed by the network, the transaction is considered final.
If someone tries to spend the same coin again, nodes will detect that the coin has already been used and reject the transaction.
The chain with the most accumulated work (usually measured by computational difficulty in proof-of-work systems) is considered the valid chain. Any attempt to create a parallel, fraudulent chain would require immense computing power, making it practically impossible on large blockchains like Bitcoin.
What is Bitcoin?
Bitcoin is a digital currency (or cryptocurrency) created in 2009 by an anonymous person or group under the name Satoshi Nakamoto. Unlike traditional money, it is not controlled by any bank or government. Transactions are recorded on a public blockchain, making the system secure and transparent.
Bitcoin transactions are grouped into blocks, and each new block must be validated by the network through a process called "mining." This process ensures that all transactions are legitimate.
An important concept in Bitcoin is the coinbase transaction. This is the very first transaction in each block, created by the miner who validated that block. This transaction awards a reward in new bitcoins to the miner, which is how new bitcoins are created. It's a bit like a "bonus" for the work done to secure the network.
Why have a Bitcoin node at home?
A Bitcoin node is a computer that downloads and stores a complete copy of the Bitcoin blockchain. This node actively participates in the network by verifying transactions and helping to secure the currency.
Having a Bitcoin node at home has several major advantages:
- Enhanced security : By using your own node, you don't depend on a third-party service to validate transactions. You check their authenticity yourself, which reduces the risk of fraud or errors.
- Privacy : A personal node helps keep your financial data private. This is because you don't reveal your addresses or habits to external servers.
- Support decentralization : Bitcoin works through a distributed network. The more independent nodes there are, the stronger the network, resistant to attack or censorship. By hosting a node, you contribute to the health and freedom of the network.
- Full control : You retain complete control of your funds and can interact directly with the blockchain without intermediaries, ensuring full transparency.
Setting up a Bitcoin node at home requires a computer with a good internet connection and sufficient storage space (around 700 GB or more). Software like Bitcoin Core makes this installation easy and makes it easy to join the network.
Links:
bitcoin.org - Official Bitcoin website
bitcoincore.org - Official Bitcoin Core Wallet (Node Bitcoin)
learnmeabitcoin.com - Explanation of Bitcoin at the Cryptographic Level by Greg Walker
bitfeed.live - Building a block of transactions (nice visual)
What is Polkadot?
Polkadot is a next-generation technology in the blockchain world. Unlike classic blockchains like Bitcoin or Ethereum, Polkadot is not a single blockchain, but a network of interconnected blockchains. Its goal is simple: to allow different blockchains to communicate with each other and work together, in a secure and decentralized way.
Why was Polkadot created?
Most blockchains are isolated: they operate as silos. For example, an app on Ethereum can't easily access data on Bitcoin. This lack of interoperability limits the potential of decentralized technologies.
Polkadot was created to solve this problem. Imagined by Gavin Wood, one of the co-founders of Ethereum, Polkadot allows different blockchain networks – even those with very different structures – to exchange information, assets, or messages seamlessly.
How does it work?
Polkadot is based on a unique architecture consisting of three main elements:
- The Relay Chain : the main chain, which secures the entire network.
- Parachains : independent blockchains that connect to the Relay Chain.
- Bridges : to connect Polkadot to external blockchains (such as Ethereum or Bitcoin).
Why is this important?
Polkadot allows:
- interoperability between blockchains,
- scalability through transaction distribution,
- flexibility with custom blockchains,
- and reduced energy consumption thanks to Proof of Stake.
Links:
polkadot.com - Official website
novawallet.io - Polkadot wallet complete with: SWAPS, Votes, Delegation, Staking, ...
https://polkadot.js.org - All types of official wallets for Polkadot
polkadot.polkassembly.io - Official DAO (Decentralized Autonomous Organization) Portal
web3.foundation - web3 foundation in Zug (Switzerland)
Wallet Generator
NovaWallet-Compatible Polkadot Wallet Generator
Mnemonic (12 words):
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