Top Blockchain Interview Questions You Should Know

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by Satavisa Pati


September 12, 2021

These blockchain questions come up during your interview !!

Blockchain is one of the hottest topics in digital technology. Every aspirant in this field will be faced with blockchain interview questions in one way or another. Here is the list of blockchain questions you need to know.

How are transactions and blocks encrypted in the Bitcoin implementation?

Bitcoin blocks are not encrypted in any way: each block is public. What prevents changes and ensures data integrity is a value called the block hash. The contents of the block are processed using a special hash function – in the case of Bitcoin, this is SHA256 – and the resulting value is included in the blockchain.

Explain why a blockchain needs tokens to function.

Coins / tokens are used to implement changes between states. When someone makes a transaction, it is a change of state and the coins are moved from one address to another. Other than that, transactions can contain additional data, and a state change is used to mutate the data – the only way to do that is in an immutable blockchain by definition. Technically, a blockchain does not need coins for its essential operations, but without them another means must be introduced to manage chain states and verify transactions.

How does peer discovery work in a peer-to-peer (P2P) network?

When a new node starts up, it does not know anything about the network, because there is no central server. Usually, developers provide a list of trusted nodes written directly in code that can be used for initial peer discovery.

How do auditors check if a block is valid?

Each complete node in the network blocks verification. When a new block is announced, each receiving node performs a checklist. The two most important checks are proof of work (whether a block provides enough work to be included in the chain) and the validity of all transactions (every transaction must be valid).

What is a scriptPubKey? Explain how a P2SH address can be spent.

A scriptPubKey is a “locking script”. It is found in the output of the transaction and is the footprint that must be filled to spend the output. P2SH is a special type of address where the complex locking script is replaced with its hash. When a transaction attempting to spend the output is presented later, it must contain the script that corresponds to the hash, in addition to the unlock script.

What is a trap function and why is it necessary in blockchain development?

A trap function is a function that is easy to calculate in one direction but difficult to calculate in the opposite direction unless you have special information. Trap functions are essential for public key encryption, which is why they are commonly used in blockchain development to represent ideas of addresses and private keys.

What is mining?

Mining is the process of reaching consensus in blockchain networks. Mining serves two purposes. First, it creates new parts in a generated block. Second, it includes transactions in a distributed ledger by providing proof of work to the network; ie proof that the generated block is valid.

What is a chain fork?

The blocks in the ledger are included so as to build the longest chain, that is, the chain with the greatest cumulative difficulty. Forking is a situation where there are two candidate blocks competing to form the longest blockchain and two miners discover a solution to the proof of work problem within a short period of time from each other. The network is then divided because some nodes get blocks from miner # 1 and others from miner # 2. A fork is usually resolved in a single block, as the likelihood of this happening again becomes extremely low with the next blocks that arise, so soon there will be a new longer chain that is considered primary.

Is blockchain totally different from traditional bank ledger?

Bank ledgers are used to ensure that transactions can run smoothly. This is why they trace and time stamp transactions. The significant difference between a bank ledger and a blockchain is how they are governed. Blockchain is decentralized in nature; however, the bank ledgers are completely centralized because the banks govern them.

What is the federated blockchain? Give examples

A federated blockchain is a blockchain managed by a group. This makes them faster and more scalable because the group dedicates the validation of transactions. To begin with, the pre-selected nodes are created by the leaders. These nodes dictate both transactions and who can participate in the blockchain. Examples include EWF, R3, etc.

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