The UTXO model

A technical cornerstone of Bitcoin

Martin Thoma
Coinmonks
Published in
6 min readFeb 17, 2021

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Visualization of a transaction. Image by Satoshi Nakamoto (Bitcoin: A Peer-to-Peer Electronic Cash System)

Bitcoin is based on the UTXO (unspent transaction output) model to ensure that nobody is able to spend money they don’t have and prevent money from being spent twice — so-called double-spending. In this article, you will learn how that works. Let’s go!

The Context

Bitcoin transactions are stored in blocks. Verifying the transactions is a crucial part of the security of Bitcoin. Another element of security is to make it computationally hard to add new blocks by adding a mathematical puzzle. In this article, you will learn how the transactions are actually validated.

If you want a longer introduction to Bitcoin / Blockchain, I’ve got you:

How Bitcoins are created

The first block of the blockchain is just defined in the code. All other blocks in bitcoin need to have a “proof of work”. This is a solution to an automatically generated mathematical puzzle that makes clever use of hash functions. Solving this hash puzzle is computationally intensive. This…

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Martin Thoma
Coinmonks

I’m a Software Engineer with over 10 years of Python experience (Backend/ML/AI). Support me via https://martinthoma.medium.com/membership