Transaction confirmation handling in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a transaction confirmation in blockchain?

A transaction confirmation means that a transaction has been included in a block and accepted by the network. Each confirmation increases trust that the transaction is permanent and won't be reversed.

beginner

Why do we wait for multiple confirmations before considering a transaction final?

Waiting for multiple confirmations reduces the risk of a transaction being reversed due to chain reorganizations or forks. More confirmations mean higher security and trust.

beginner

What is a common number of confirmations to wait for in Bitcoin before accepting a transaction as final?

Typically, 6 confirmations are considered safe in Bitcoin to ensure the transaction is permanent and irreversible.

intermediate

How can a program detect when a transaction is confirmed?

A program can listen to blockchain events or query the blockchain to check if the transaction hash appears in a block and count how many blocks have been added after it.

intermediate

What is a chain reorganization and how does it affect transaction confirmations?

A chain reorganization happens when a longer blockchain replaces a shorter one, potentially removing some blocks. This can cause previously confirmed transactions to become unconfirmed temporarily.

What does one confirmation of a blockchain transaction mean?

A The transaction is reversed

B The transaction is sent to the network

C The transaction is rejected

D The transaction is included in a block

One confirmation means the transaction is included in a block on the blockchain.

Why is it safer to wait for multiple confirmations?

A To reduce risk of transaction reversal

B To speed up the transaction

C To increase transaction fees

D To avoid paying taxes

Multiple confirmations reduce the chance that a transaction will be reversed due to chain reorganizations.

How many confirmations are commonly considered safe in Bitcoin?

A 3

B 6

C 1

D 10

6 confirmations are commonly accepted as safe for Bitcoin transactions.

What can cause a confirmed transaction to become unconfirmed?

A Wallet backup

B Transaction fee increase

C Chain reorganization

D Mining difficulty drop

Chain reorganizations can remove blocks, causing transactions to lose confirmations temporarily.

Which method can a program use to check transaction confirmations?

A Query blockchain for transaction block and count subsequent blocks

B Send email to miner

C Check wallet balance only

D Restart the blockchain node

Programs check confirmations by finding the block containing the transaction and counting how many blocks came after it.

Explain what transaction confirmations are and why they matter in blockchain.

Think about how blocks build on each other to secure transactions.

Describe how a program can detect when a blockchain transaction is confirmed.

Consider how the blockchain data can be accessed and monitored.