Blockchain

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A blockchain is a growing list of records, called blocks, that are linked together using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree). The timestamp proves that the transaction data existed when the block was published in order to get into its hash. As blocks each contain information about the block previous to it, they form a chain, with each additional block reinforcing the ones before it. Therefore, blockchains are resistant to modification of their data because once recorded, the data in any given block cannot be altered retroactively without altering all subsequent blocks. Blockchains are typically managed by a peer-to-peer network for use as a publicly distributed ledger, where nodes collectively adhere to a protocol to communicate and validate new blocks. Although blockchain records are not unalterable as forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.Wikipedia

How Does It Work?

Behind blockchains & cryptocurrencies

A Complete Visual Walkthrough into How Blockchains Work, full episode with Anders Brownworth
Real Vision crypto editor Ash Bennington welcomes Anders Brownworth to walk through a step-by-step of how blockchains work. Brownworth explains the basics of hashing, blocks, and then blockchains, demonstrating how each piece builds upon the other to create the underlying technology of cryptocurrencies. Filmed on May 20, 2021. Key Learnings: Those who are unfamiliar with blockchain technology can experience a steep learning curve when trying to understand how it works—Brownworth breaks it down into a simple, easy-to-digest format with visual aids that allow the viewer to conceptualize blockchain technology. Thanks for watching Real Vision Crypto!

But how does bitcoin actually work?
The math behind cryptocurrencies. Help fund future projects: https://www.patreon.com/3blue1brown An equally valuable form of support is to simply share some of the videos. Special thanks to these supporters: http://3b1b.co/btc-thanks This video was also funded with help from Protocol Labs: https://protocol.ai/join/ Some people have asked if this channel accepts contributions in cryptocurrency form. As a matter of fact, it does: http://3b1b.co/crypto

Blockchain 101 - A Visual Demo
This is a very basic visual introduction to the concepts behind a blockchain. We introduce the idea of an immutable ledger using an interactive web demo.

Blockchain 101 - Part 2 - Public / Private Keys and Signing
This is part two in my basic visual introduction to the concepts behind a blockchain. We build on the concepts from the previous video and introduce public / private key pairs and signing using an interactive web demo.

SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the Merkle–Damgård construction, from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher. ..The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits... .SHA-2 was first published by the National Institute of Standards and Technology (NIST) as a U.S. federal standard (FIPS). The SHA-2 family of algorithms are patented in US patent 6829355. The United States has released the patent under a royalty-free license. | Wikipedia

Introduction

A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution. Digital signatures provide part of the solution, but the main benefits are lost if a trusted third party is still required to prevent double-spending. We propose a solution to the double-spending problem using a peer-to-peer network. The network timestamps transactions by hashing them into an ongoing chain of hash-based proof-of-work, forming a record that cannot be changed without redoing the proof-of-work. The longest chain not only serves as proof of the sequence of events witnessed, but proof that it came from the largest pool of CPU power. As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they'll generate the longest chain and outpace attackers. The network itself requires minimal structure. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will, accepting the longest proof-of-work chain as proof of what happened while they were gone. Bitcoin: A Peer-to-Peer Electronic Cash System | Satoshi Nakamoto - bitcoin.org


Programming

Uses

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Supply Chain

Blockchain use cases for supply chain include immutability into the provenance of goods, the elimination of reconciliation pain across multiple parties and the real-time visibility to perform track and trace analysis, assess risks and accelerate physical and financial supply chains. Blockchain for supply chain management: use cases and applications | r3

Distributed Ledger

A distributed ledger is a database that is consensually shared and synchronized across multiple sites, institutions, or geographies, accessible by multiple people. ... Underlying distributed ledgers is the same technology that is used by blockchain, which is the technology that is used by bitcoin.