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Intermediate Topic 18 of 51 Emerging & Frontier Topics

Blockchain

Append-only ledger shared among distrusting parties.

How it works

A blockchain is an append-only ledger replicated across many computers. Transactions are grouped into blocks, and each block contains a hash of the previous block, so altering old data changes every later hash and is quickly detected. Participants run nodes that validate transactions and agree on the next block through a consensus mechanism, which removes the need for a trusted central party. Digital signatures prove who authorized a transaction, Merkle trees summarize the transactions in a block efficiently and networks may be public and permissionless, as in Bitcoin and Ethereum, or private and permissioned.

Where it is used

It is used for cryptocurrencies, asset tracking, settlement between organizations and tamper-evident records.

Common pitfall

Blockchains are slow and costly compared with databases, immutability makes mistakes permanent and many proposed uses do not need one. Ask whether several untrusting parties really must share a ledger before using one.

Where it fits in the course

Blockchain is topic 18 of 51 in Emerging & Frontier Topics, rated Intermediate. It follows Data Mining. The next topic is Proof of Work and Proof of Stake.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Emerging & Frontier Topics quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Blockchain?
Append-only ledger shared among distrusting parties. It belongs to Emerging & Frontier Topics and is an intermediate-level topic.
Where do people use Blockchain?
It is used for cryptocurrencies, asset tracking, settlement between organizations and tamper-evident records.
What is the most common mistake with Blockchain?
Blockchains are slow and costly compared with databases, immutability makes mistakes permanent and many proposed uses do not need one.
What should I learn before this topic?
Start with Data Mining, the topic just before it in Emerging & Frontier Topics.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Emerging & Frontier Topics quiz.
Is Blockchain hard to learn?
It is an Intermediate topic. Be comfortable with the Beginner topics in this area first, then read the common pitfall carefully, since it is where most mistakes happen.
How long does it take to learn Blockchain?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Blockchain?
Data Mining, Proof of Work and Proof of Stake, Big Data are closely connected. The full list is in the related topics section of this page.
What should I study after Blockchain?
Continue with Proof of Work and Proof of Stake, the next topic in Emerging & Frontier Topics.

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