Cryptocurrency Explained: Understanding Double-spend, Block Re-Organization, & Consensus [Bitcoin] @aantonop
Cryptocurrency Explained: Understanding Double-spend, Block Re-Organization, & Consensus [Bitcoin]  @aantonop
Uploaded January 2021 | Updated September 2026, 1 hour ago
Today there were headlines about a "double-spend" in bitcoin! Many took that to mean that bitcoin has a catastrophic flaw (it doesn't) or the network is not secure (it is) or that bitcoin is somehow broken (it's not). Watch this video to learn the truth about what a double-spend is, what it's not, and how to separate FUD from facts. tl;dw: Nothing abnormal happened.

Chapters
0:00 Did a double spend happen on bitcoin?
1:31 What happened?
5:46 Miners are competing
18:53 2 competing blockchains
20:47 Consensus fork
22:41 How is consensus fork resolved?
26:10 What it means when someone says my transaction has confirmation
27:25 This process ensures that double spends are not successful
28:53 2 miners found 2 blocks simultaneously and broadcast them
29:17 Bitmex research and monitoring
29:58 What happens to transactions in those 2 blocks?
32:33 The Mempool
34:42 Double spend attempt
38:19 This doesn't matter for small amounts
41:47 Risk assessment
43:28 I would sell my house for 0 confirmation
44:56 Miners will take the most fee they can
48:59 How do we move forward? It seems fake news is becoming a major problem within bitcoin.
53:39 Do you think it's easier to "fake articles" about bitcoin than it is about anything else? Given the complexity of the blockchain and how so many people that hold bitcoin don't really understand it
54:23 Was it the same transaction in the two blocks? It seems the amount spent is different. If yes, could it be indicative of someone deliberately trying to spend the same bitcoin twice and testing waters if there was some protocol flaw?
56:59 In my opinion what happened is too unlikely without being premeditated. Maybe someone has been propagating two different transactions like these for a long time until he finally got lucky and they were precisely included in 2 competing blocks
58:22 Would a node continuously propagating competing transactions get banned from connecting to the peer-to-peer network?
1:01:11 I think it would be beneficial to explain how a merchant should treat a bitcoin transaction and how the number of confirmations to wait before accepting a transaction should possibly scale.
1:10:21 Can Proof-of-Work provide immediate block finality like modern Proof-of-Stake algorithms
1:12:29 Why the clickbait title?
1:13:43 Announcement - Open topic Q&A
1:14:16 One of the solutions to confirmations is the lightning network
1:15:55 Conclusion

Are you interested in really understanding bitcoin? In this video, aantonop (one of the most trusted, unbiased sources of crypto info) answered questions bitcoin transactions, network double spends, how consensus works, and much more. Don’t miss Andreas' version of what happens if you let someone drive away with your car after only 1 confirmation.

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Cryptocurrency Explained: Understanding "Double-spend", Block Re-Organization, & Consensus [Bitcoin]

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