What is Double Spending

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A short and simple explanation about the nature of Bitcoin double spending and how to avoid it.

What is Double Spending

18 Kommentare

    thanks for the great video,, i have two question that i couldn’t figure out
     how double spending can be bypassed? suppose the attacker has more CPU power than the honest nodes, he will generate a blockchain that is Not the same as the other nodes‘ block-chain; it’s supposed to be easily detected?(for example, the attacker changed the ledger by  generating a block that is 4 blocks before the last block and continued redoing the rest) even though he did a proof-of-work,, the block chain generated and broadcasted will NOT be the same as the block chain stored in honest nodes‘ computers. so how it can double spending be bypassed?? isn’t supposed to lead to inconsistency between the attacker’s generated blockchain and the other’s ones?

    also, how the longest chain is identified?

    1. Well it is harder. You’ll have to get 51% of all of the networks computing power – this means something like a few million computers…

    2. +Ofir Beigel But thats not the point,one of the big perks people are saying is bitcoin „counterfeit proof“ but as you know,if their is a will their is a way. Doubt it would take a million computers given the right intelligence. 

  2. is it not possible to reduce the balance from the account when the first transaction of 1 bitcoin is done on the account until there are further funds to do any more transactions ?

    1. Dialectical Monist the more I learn about it the less I like the idea of a „decentralized“ currency with a perfect track record of every transaction, that’s available to anyone in the network. Add to that the anonymity of its creator(s) and there’s reason for concern. It’s reasonable to assume it’s going to be superseded by better tech, but the concerns remain still.

    2. A node is basically like a small computer connected to the gigantic computer (i.e., Blockchain System). Treat that the bitcoin network (or ethereum etc.,) as a one very big computer and every system or machine that is connected is termed as node connected to that machine. Nodes are responsible for mining (but mind you not all nodes have to be mining) and serve the purpose of security. The more nodes are connected to the network, the more secure that network is. I hope this makes some sense in simple layman terms.

    3. You are only seeing the tip of the huge iceburg. Bitcoin is only one of several blockchain technologies out there. If you want complete anonymity its possible with other coins like Monero, ZCash etc., Anonymity of the creator should not worry you, because he/she doesn’t hold anything for what you hold in the network. Ofcourse, no technology will be there for life time, it only gets better. We ain’t using Java, which is now more or less overtaken by better like NodeJs etc., Bitcoin is only for currency, you have betterment stuff like ethereum, cardano, IOTA etc., now we can neither say these will stay there forever, can easily be overtaken by something that can be quantum resistant and future hack resistant. Sometimes, it takes time to get our head around things that are so complex in nature, the only way for us to overcome it is to have very thorough understanding and it will take a bit of time. Keep hitting the same thing again and again and you will surely understand the stuff around blockchain, it ain’t rocket science either. All the best buddy.

  3. Is it possible you can look a a transaction i did its been pending for 3 days now and has 670 confirmations and says pending in my account but i know for a fact i did not send it 2 times so it doesn’t make sence im wondering if i was hacked or what but if you contact me i will send you the id hash

  4. Great Video! One question though: what if both transactions get into the same block? Is the whole block invalid and doesn’t get added into the Blockchain?

    1. Excellent thinking Jim. If two or more transactions spend the same input to the same block, bitcoin automatically rejects both transactions to prevent one Bitcoin from going toward two separate ends. If its the other case where the double spend is sent to different blocks, as more confirmations are gathered one of the transactions will be rejected, which is covered beautifully in this video already.

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