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Mastering Blockchain, Fourth Edition

You're reading from   Mastering Blockchain, Fourth Edition Inner workings of blockchain, from cryptography and decentralized identities, to DeFi, NFTs and Web3

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Product type Paperback
Published in Mar 2023
Publisher Packt
ISBN-13 9781803241067
Length 818 pages
Edition 4th Edition
Languages
Concepts
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Author (1):
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Imran Bashir Imran Bashir
Author Profile Icon Imran Bashir
Imran Bashir
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Table of Contents (24) Chapters Close

Preface 1. Blockchain 101 FREE CHAPTER 2. Decentralization 3. Symmetric Cryptography 4. Asymmetric Cryptography 5. Consensus Algorithms 6. Bitcoin Architecture 7. Bitcoin in Practice 8. Smart Contracts 9. Ethereum Architecture 10. Ethereum in Practice 11. Tools, Languages, and Frameworks for Ethereum Developers 12. Web3 Development Using Ethereum 13. The Merge and Beyond 14. Hyperledger 15. Tokenization 16. Enterprise Blockchain 17. Scalability 18. Blockchain Privacy 19. Blockchain Security 20. Decentralized Identity 21. Decentralized Finance 22. Blockchain Applications and What’s Next 23. Index

The DAO

The Decentralized Autonomous Organization (DAO), started in April 2016, was a smart contract written to provide a platform for investment. Due to a bug in the code, called the reentrancy bug, it was hacked in June 2016. An equivalent of approximately 3.6 million ether was siphoned out of the DAO into another account.

Even though the term “hacked” is used here, it was not really hacked. The smart contract did what it was asked to do but due to its vulnerabilities, the attacker was able to exploit it. It can be seen as an unintentional behavior (a bug) that the programmers of the DAO did not foresee. This incident resulted in a hard fork on the Ethereum blockchain, which was introduced to recover from the attack.

The DAO attack exploited a vulnerability (reentrancy bug) in the DAO code where it was possible to withdraw tokens from the DAO smart contract repeatedly before giving the DAO contract a chance to update its internal state, indicating how many...

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