Intro to Blockchain Technology

Types of Blockchains

Blockchain is a distributed database that maintains a continuously growing list of data records secured from tampering and revision. Blockchain is the main technology behind bitcoin, where it serves as the public ledger for bitcoin transactions. Many altcoins emerged after the rise of bitcoin. Blockchain technology is the backbone of all of them. After people started to understand how a blockchain works, they started using it for other purposes, like to store value, identities, agreements, property rights etc. Ethereum is the biggest innovation after bitcoin. It provides a way to create online markets and programmable transactions known as smart contracts. Three main types of blockchains exist:

# Public blockchains
Anyone in the world can read, anyone in the world can send transactions to and expect to see them included if they are valid, and anyone in the world can participate in the consensus process – the process for determining what blocks get added to the chain and what the current state is. Public blockchains are open-source and everyone can be part of them. Anyone in the world can explore the blockchain, send transactions or contracts, consult them and participate in the consensus process – the process for determining what blocks get added to the chain and what the current state is.
Examples: Bitcoin, Ethereum
Find a list of all publicly listed blockchains and their market cap here.

# Consortium blockchains
Consensus process is controlled by a pre-selected set of nodes; for example, one might imagine a consortium of 15 financial institutions, each of which operates a node and of which 10 must sign every block in order for the block to be valid. The right to read the blockchain may be public, or restricted to the participants.
Example: R3

# Private blockchains
Write permissions are kept centralized to one organization. Read permissions may be public or restricted to an arbitrary extent. Likely applications include database management, auditing, and more that are internal to a single company, and so public readability may not be necessary in many cases at all, though in other cases public auditability is desired.
Examples: Eris Industries, Multichain

Source: Ethereum Blogpost


Source:, chris skinner’s blog



On 31 October 2008 an anonymous person or a group called Satoshi Nakamoto introduced the idea of bitcoin. The system is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain, which uses bitcoin as its unit of account.
Characteristics: consensus mechanism: Proof of Work (PoW); type of blockchain: public blockchain



Ethereum is an open blockchain platform that lets anyone build and use decentralized applications that run on blockchain technology. It was introduced by Vitalik Buterin in late 2013 and was formally announced on January 25, 2014. Since then Ethereum has been used as a platform for decentralized applications (dApps), decentralized autonomous organizations (DAOs) and smart contracts.
Characteristics: consensus mechanism: PoW (future plans include moving to Proof of Stake(PoS) algorithm); type of blockchain: public blockchain.



Dash (DASH) is a privacy-centric digital currency with instant transactions. It is based on the Bitcoin software, but it has a two tier network that improves it. Dash allows you to remain anonymous while you make transactions, similar to cash.
Characteristics: consensus mechanism: PoW; type of blockchain: public blockchain



Lisk is a public blockchain platform that provides decentralized blockchain apps. The idea is that every blockchain app is on its own sidechain, separate from the main blockchain. This should help with scalability issues that many cryptocurrencies were facing, such as bitcoin.
Characteristics: consensus mechanism: delegated proof of stake (DPoS); type of blockchain: public blockchain



Steem is designed around a relatively simple concept: everyone’s meaningful contribution to the community should be recognized for the value it adds . Steem aims to support social media and online communities by returning much of its value to the people who provide valuable contributions by rewarding them with cryptocurrency.
Characteristics: consensus mechanism: PoW; type of blockchain: public blockchain



Ripple is a real-time gross settlement system (RTGS), currency exchange and remittance network based upon the Ripple Labs version of blockchain. Ripple’s distributed financial technology allows for financial institutions around the world to directly transact with each other without the need for a central counterparty or correspondent. It works with any currency (dollars, euros, yen, etc.), and it settles transactions, including cross-currency transactions.
Characteristics: consensus mechanism: Ripple Protocol consensus algorithm (RPCA); blockchain type: private blockchain


mjkIntro to Blockchain Technology