Topic: Some Bitcoin question (Read 542 times)

That solves the problems. Thanks a lot!

Correct.

Someone can publish a replacement for a block that is 10 blocks deep in the blockchain.  However, no peers will accept it unless it is first solved for a SHA256(SHA256(block_header)) result that is lower than the target difficulty.  Then, since the SHA256(SHA256(block_header)) of the block is a field in the block_header of the next block (creating a "chain" of blocks), the value of SHA256(SHA256(block_header)) for the block 9 blocks deep will no longer be lower than the target difficulty.  Therefore the publisher of the replacement block would also have to publish a new block 9 blocks deep after solving for a new SHA256(SHA256(block_header)) for that block.  Of course that hash will need to be included in the block_header of the block that is 8 block deep, which will alter the value of its SHA256(SHA256(block_header)).  This continues until you get all the way up to the most recent block.  Then the publisher of the altered chain still has to solve one more brand new block to create a chain that is "longer" than the chain that all their peers already have.

While the publisher of the altered chain is solving all these previous blocks, the rest of the network is continuing to solve new blocks.  Therefore, the publisher of the altered chain has to be able to solve blocks faster then the rest of the entire network combined, or they will never catch up.  Since the rate at which a miner solves blocks is largely dependent on the amount of hashing power they supply, the publisher of the altered chain would have to spend a lot of money to acquire a significant percentage of the mining equipment in the world, and then they'd have to spend a lot of money on electricity to run that equipment until their altered chain grew longer then the current chain.

Thanks for the response!


Suppose there're 10 blocks, the top most block named 1, the lower one 2 etc....

What you're trying to say here, is that it's always possible to create a fork of the 10th block, i.e. branch the chain from the 10th block, but that would require to solve all blocks above it (10th, 9th, 8th, 7th ...) and it's length should exceed the current longest chain.

Danny is a machine - a living encyclopedia.

I've been here a few months now, and Danny has non-stop answered questions here fully and detailed.

I'll most definitely give you some coins when I make some, lol.

K.

No.


No.


Not exactly, but that's a much better analogy.


The wallet address is computed from the public key.  Many people refer to it as a hash of the public key.  In actuality, it is a hash of a hash of a public key concatenated with a checksum.
https://en.bitcoin.it/wiki/Technical_background_of_Bitcoin_addresses


I'm not sure what you are asking.  A block cannot be modified without modifying ALL the blocks that came after it.  In modifying all of those blocks, you would also have to solve every one of them for a SHA256(SHA256(block_header)) result that was lower than the target difficulty.


Considered how?  Any transactions that were in the orphaned blocks that are not in the current chain would return to the memory pool to be added to other blocks later.


Any block reward from an orphaned block vanishes from existence.

Hello everyone!

This's my first post so in the newbie forum, please tell me if I have to repost this in another forum in order to get proper answers, or please move it to the right forum (mods).

I was learning about Bitcoin, so there are a few question I'ld like to ask.

Firstly, does each Bitcoin have an identity like currency notes? For e.g. can we say that Bitcoin x is held by an address X, and bitcoin y is held by an address Z? Or is it that accountancy is done purely on basis of quantity of Bitcon held by different entities?

Is the wallet address the same as the public key?

Can a block (z) which's under many/one block be 'unlocked'? Or is modifying the block possible by giving an alternative and more difficult solution to the  block previous to z? If so, why is such a feature present?

Suppose there're 2 solutions provided to a block simultaneously, and one of the branches is abandoned cause the other was clearly ahead. Will the blocks of the abandoned chain be considered by the network or will they just be ignored. A related question -- will the miners of the blocks which belong to the shorter branch (which was abandoned) will earn bitcoins?