# QNA

1. The potential creation of fake nodes to control 51% of the network.

2. The risk of altering blocks within the chain. \
   solution: Hashing algorithm

3. The addition of fraudulent new blocks by malicious miners.\
   Solution: POW , POS

4. Potential vulnerabilities in the SHA-256 algorithm.

5. The issue of double spending, which requires more than 51% node consensus and significant computational power.

6. Uneven distribution of rewards among miners when more than 50% of nodes validate a transaction, potentially leaving others with excess computational power. Additionally, how does this impact the processing of other transactions in the queue?"

7. How do nodes validate transactions in a blockchain?

8. How is a new block added to the blockchain, considering that each block contains multiple transactions?

9. What happens if two blocks attempt to be added to the blockchain at the same time?

10. What is the typical number of transactions stored in a single block?

11. How does the verification process for transactions differ from that of a block? Are they distinct processes, or are they the same?

12. When a block is being verified, does this process also involve verifying the transactions contained within that block?

13. Since multiple miners are mining and selecting transactions or blocks from the mempool, do they end up with different sets of transactions? If so, does this result in the creation of multiple different blockchains? How is this situation managed in the blockchain ecosystem?

14. How do fellow miners authenticate the block produced by the successful miner within the network? How do other nodes confirm the transaction solution provided by the miner? Why is validation often perceived as challenging while verification is relatively straightforward? What sets apart the process of validating transactions from the act of miners verifying transactions?

15. What if a node deliberately provides incorrect information about the successful miner to other miners in an attempt to ban that successful miner from the network? Since this is a peer-to-peer (P2P) network, the successful miner cannot establish direct connections with other nodes.

16. **What determines the unique hash ID for each block in a blockchain, and is it possible to predict this hash ID or the nonce in advance?**\\

    The unique hash ID for each block in a blockchain is determined by the block header, which contains the following information:

    * Version number of the block
    * Hash of the previous block
    * Merkle root hash of all the transactions in the block
    * Timestamp
    * Nonce

    The nonce is a random number that miners use to try to find a hash that meets the target difficulty. It is impossible to predict the hash ID or the nonce in advance because the hash function is designed to be unpredictable.

17. **How do nodes validate transactions in a blockchain?**

    Nodes validate transactions by verifying the following:

    * The digital signatures of the sender and receiver are valid.
    * The sender has sufficient funds to cover the transaction amount.
    * The transaction has not already been spent (double spending).

    Nodes can efficiently verify transactions using a Merkle tree, which is a data structure that allows them to verify the authenticity of a large number of transactions without having to verify each one individually.

18. **What happens if two blocks attempt to be added to the blockchain at the same time?**

    If two blocks attempt to be added to the blockchain at the same time, the network will temporarily split into two chains. This is known as a fork.

    Eventually, one of the two chains will become longer than the other. When this happens, the shorter chain will be abandoned and all of the nodes on the network will switch to the longer chain.\\

19. ### **Blockchain Mining**

    Why blockchain is not fully secure ?\
    1\. Create fake nodes which covers 51 % of the blockchain network.\
    2\. Change the block in middle\
    3\. Add new fake block, if miner is an hacker\
    4\. Hacker the sha256 algorithm\
    5\. Double Spending Problem: In this solution more than 51% node will be correct other will reverted their transaction of added Tx to the block , again additional power need. Kuch jaayda karcha nhi ho rha ?\
    6\. Once a transction happened more than 50% node validate that thing to add into the blockchain, but one will be the miner who will get the rewards , only one person what about others why they have given unncessary computational power.\
    If more than 50% per nodes are working on one transaction then what about other transaction that means they will come one by one ?
