Blocks, chains, and hashing in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a block in a blockchain?

A block is a container that holds a list of transactions and some metadata like a timestamp and a reference to the previous block.

beginner

Why do blocks form a chain in blockchain?

Blocks form a chain by linking each block to the previous one using a reference called a hash, creating a secure and ordered sequence.

beginner

What is hashing in the context of blockchain?

Hashing is a process that turns data into a fixed-size string of characters, which acts like a digital fingerprint for the block's content.

intermediate

How does hashing help secure the blockchain?

Hashing makes it easy to detect changes because even a tiny change in the block data changes the hash completely, breaking the chain if tampered.

intermediate

What is the role of the previous block's hash in a new block?

It links the new block to the previous one, ensuring the chain's order and integrity by making blocks dependent on each other.

What does a block in a blockchain typically contain?

A A list of transactions and a reference to the previous block

B Only a list of transactions

C Only a timestamp

D User passwords

A block contains transactions and a reference (hash) to the previous block to form the chain.

What is the purpose of hashing in blockchain?

A To encrypt user data

B To create a unique fingerprint of block data

C To speed up transactions

D To store passwords

Hashing creates a unique fingerprint that represents the block's data.

What happens if data in a block changes after hashing?

A The block deletes itself

B Nothing changes

C The previous block changes

D The hash changes, breaking the chain

Any change in block data changes its hash, which breaks the chain's integrity.

How does a blockchain ensure the order of blocks?

A By linking each block to the previous block's hash

B By using timestamps only

C By sorting blocks alphabetically

D By user approval

Each block contains the previous block's hash, linking them in order.

Why is the chain structure important in blockchain?

A It hides data from users

B It makes transactions faster

C It secures data by making blocks dependent on each other

D It stores user passwords

The chain structure ensures security by linking blocks so tampering is obvious.

Explain how blocks are linked together in a blockchain and why this is important.

Think about how a chain is formed by connecting links.

Describe what hashing does in a blockchain and how it helps keep data secure.

Imagine a fingerprint that changes if you change even a small detail.