Key Concepts of Cryptocurrency

Cryptocurrencies use blockchain networks and cryptography to enable digital asset transfers without relying on a single central operator. We'll dive into how cryptocurrencies work, including blockchain, cryptography, and digital wallets. Understanding these concepts can help you follow how blockchain networks record transactions and how wallets control access to assets.

Blockchains record transaction history across a network of computers, and account balances can be derived from that history. Cryptography is used to create key pairs and digital signatures, which help authorise transactions from an address. Consensus mechanisms help distributed participants agree on the order of transactions without needing a single trusted administrator.

As you can see, things are about to get a bit technical. Don't worry, we'll explain it in simple terms before diving deeper. 

A blockchain is a shared ledger used to record transactions in a way that can be independently verified by network participants. It consists of data blocks linked together, forming a ledger where changing past records is difficult because later blocks depend on earlier data. To understand blockchain, it helps to compare it to traditional banking. Banks keep private ledgers with our account balances and transactions. If we want to send money, we ask the bank to debit one account and credit another. We trust banks as the record-keeper and authority. 

Many public blockchains do not rely on a central authority. They use cryptography and consensus mechanisms so participants can verify the ledger without trusting a single intermediary.
 

The blockchain ledger is decentralized across a peer-to-peer network.It works like a distributed database maintained by many nodes, each storing and validating a copy of the ledger. This can reduce reliance on a central authority and may improve transparency and integrity, depending on the network design.

New transactions are grouped into blocks and added to the chain at regular intervals that vary by network (for example, Bitcoin averages about 10 minutes per block). Each block contains key details - the transactions, a unique code called a "hash," timestamps, and more. The hashes link the blocks together in a specific order, forming an ongoing chain.  

Depending on the consensus mechanism, blocks are proposed and validated by miners (proof of work) or validators (proof of stake).  This can make rewriting transaction history difficult without significant cost or control over the network’s consensus. However, no system is immune to attacks or failures.

Instead of a central server, a peer-to-peer network of participants maintains the blockchain. Thousands of nodes store identical copies of the ledger and work together to update new transactions.  

There's no single point of failure, providing high availability, redundancy, and uptime. If some nodes fall offline, the network keeps humming along. This gives blockchain extraordinary resilience.  

The blockchain design enables several key features:  

• Transparency - On many public blockchains, transactions are visible, including the sending and receiving addresses and amounts. Identities are not inherently public, but activity can sometimes be linked to real people through exchanges, analytics, or reuse of addresses.
• Immutability - It's incredibly difficult to modify historical records. Cryptography, like hashing, secures the chronological order.  
• Decentralization - No single entity is intended to control the ledger, though real-world decentralisation depends on node distribution, mining/validator concentration, and governance.
   

Let's walk through what happens when Mike sends Amy 5 coins on the blockchain:  

1. Mike's wallet software initiates a new transaction request to send Amy's address the 5-coin payment amount. This transaction request enters the memory pool.  
2. Miners compile pending transactions from the memory pool into a candidate block for the next chronological position.  
3. Miners race to solve a cryptographic puzzle needed to add the block. The first to solve claims a small reward.  
4. The winning miner announces the solution across the peer-to-peer network for validation. Nodes check the work before accepting the new block.  
5. Consensus is reached when nodes accept the block under the network’s consensus rules. In proof of work networks like Bitcoin, this is typically based on the chain with the most accumulated work, not a “50% of nodes” vote. Once confirmed, the network recognises the transaction as valid, and Amy’s address is credited according to the ledger rules (wallet apps then display updated balances).
    

Everything you just read happens on the blockchain. For Bitcoin’s Network for example, the whole process repeats about every 10 minutes with a new block of transactions. This forms a historical chain providing proof that Mike sent Amy money. (Note that this is only one type of consensus known as “proof of work”; as we'll see later on, there are others.)  

Cryptography makes up the nuts and bolts of cryptocurrency technology. It enables the security framework around blockchain transactions and consensus mechanisms.  

You can think of cryptography as encoded messaging in cryptocurrencies. Most public blockchains do not encrypt transaction details. Instead, users sign transactions with private keys, and anyone can verify signatures using public keys. Cryptographic methods are used to secure transactions and verify access according to protocol rules.

 Hash functions are important cryptographic techniques used extensively in blockchain. They take an input like a digital file or transaction details and run it through a special mathematical algorithm.  

The algorithm transforms the data into a fixed-length alphanumeric output called a "hash value" or just "hash." This hash represents the source data to identify, organize, and verify it.  

Hashes have some useful and desirable qualities:  

• Deterministic - Running the same input through the algorithm always returns the exact same hash output.  
• Quick computation - Hashing can encode large amounts of data very fast.  
• Preimage resistance - It's near-impossible to reverse the hash back into the original input data.  
  For example, Bitcoin uses the SHA-256 algorithm, which generates a 64-character hash. Even the tiniest change to the input data significantly alters the hash. This helps detect any chain modifications.  

Blockchains also use public key cryptography for authenticating transactions. Users share an address (derived from public key data, depending on the blockchain) so others know where to send funds.

The corresponding private keys provide the digital access needed to authorize outgoing payments. Owners store these locally, usually with password protection. In essence, private keys prove "ownership," allowing funds to be transferred out.  

Senders can also digitally "sign" transactions with their private keys. Combined with public keys, recipients can decode and validate the signatures to verify identities.  

Overall, public-private key pairs enable secure peer-to-peer value exchange without overlapping account logins. The cryptographic workflows facilitate transparency and accuracy across the distributed ledger.  

Consensus mechanisms provide the security and governance models for blockchain networks. They allow distributed nodes to reach an agreement while preventing cheating or manipulation. This facilitates community trust and growth.  

There are a variety of methods, each with its own strengths and applications. Let's examine two major ones:  

Proof of Work and Proof of Stake.  

In Proof of Work (PoW) systems, powerful participants called "miners" race to validate blocks of transactions and write them to the blockchain. More computing power gives miners a higher chance of solving quickly. Difficulty auto-adjusts based on the total power to keep block times consistent.  

Bitcoin pioneered PoW, which provides network security commensurate with computing energy spent.  

An alternative called Proof of stake (PoS) uses validators who commit tokens (stake) under protocol rules; selection and rewards depend on the network’s design.

Validators take turns proposing and voting on the next block. Little computing energy gets used in this case. Security is influenced by economic incentives tied to staked assets, depending on the network design. Ethereum is the most well-known network running on PoS.  
 

Many next-gen blockchains also utilize:  

Byzantine Fault Tolerance (BFT)  

Other consensus models include Byzantine fault tolerant (BFT) designs. “Byzantine Generals” is a classic distributed-systems problem; BFT protocols aim to keep the network functioning even if some participants fail or act maliciously. BFT ensures consensus can be achieved as long as the majority of nodes are honest. Some networks use BFT-style consensus designs (or variants) to support faster finality, but implementations vary by protocol.

Proof of Burn  

Proof of burn involves destroying tokens to demonstrate economic commitment, but it is not the same as proof of stake and does not inherently guarantee “deflationary” outcomes.

Delegated Proof of Stake (DPoS)  

In this model, token holders vote to select a fixed number of leaders known as "delegates" to validate blocks and govern the blockchain. Stakeholders vote for candidates based on trust. The delegate nodes each take turns creating blocks in a round-robin fashion. This layered voting approach results in quick transactions and efficiency.  

In conclusion, understanding the key concepts of cryptocurrency, from blockchain technology to cryptography and consensus mechanisms, is crucial in grasping how these digital assets function. As you explore this innovative financial landscape, remember that blockchain can provide transparency and security without relying on a single central authority, depending on the network. Cryptographic techniques are used to secure and verify transactions while various consensus models maintain network integrity. Understanding blockchain, cryptography, and consensus mechanisms can help you follow how cryptocurrencies work and what trade-offs different networks make.

Further Readings

• What is Cryptocurrency?
• A Brief History of Cryptocurrency
• Ethereum Transition: Impact and Significance