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Blockchain Demo

A web-based demonstration of blockchain concepts.

Blockchain 101 - 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 that is available here:


Get the code:

git clone

Install dependencies:

cd blockchain-demo
npm install

Run the server:

npm start



#For windows: if the above command didn't work, use this (make sure you have Node.js installed in your system):

node ./bin/www      

Point a web browser at the demo:


Setup using Docker

Get the code:

git clone

Run the Docker setup:

cd blockchain-demo
docker-compose up -d

Point a web browser at the demo:


Optional Configuration

You can adjust the "number of zeros" required by the demo by editing the first two lines of public/javascripts/blockchain.js.

Because there are 16 possible characters in a hex value, each time you increment the difficulty by one you make the puzzle 16 times harder. In my testing, a difficulty of 6 requires a maximumNonce well over 500,000,000.

If you adjust the difficulty above 4, blocks will show up as not mined because the demo data assumes 4 zeros for a signed block. For example, on the http://localhost:3000/block page with a difficulty of 6, the first nonce that works is 8719932 yielding a hash of 000000669445c22167511857d8f3b822b331c3342f25dfdcb326e35c1a7aa267.

In the production bitcoin blockchain, block 458091 has the hash digest 00000000000000000000011246f099d94f91628d71c9d75ad2f9a06e2beb7e92. That's 21 zeros in a row!

Public Private Key Demo

The 2nd part of the 101 session:

Send Thanks

Bitcoin gratefully accepted: 1K3NvcuZzVTueHW1qhkG2Cm3viRkh2EXJp

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