- Nothing-at-Stake problem
- Validator fraud
- Wealth concentration
- Double spending
- Staking pools

Concerns regarding Proof-of-Stake

- Restricting access to update the blockchain
- Sufficiently low block rewards
- Sufficiently modest block reward schedule

Conditions for generating consensus with Proof-of-Stake

- Ability to generate consensus with low block rewards
- Scalability without incurring greater computational costs

Advantages of Proof-of-Stake

- Follow-the-Satoshi (FTS) algorithm
- Digital Signature Scheme (DSS)

Implementations of Proof-of-Stake

- Peercoin blockchain
- Nxt blockchain
- Decentralized applications (dApps)
- Algorand


Proof-of-Stake in practice

The Follow-the-Satoshi algorithm divides time into periods called time slots. Only one block can be added to any blockchain branch in any given slot.

Time slots in Proof-of-Stake

This consensus mechanism depends on selecting validators by their proportion of holdings. Cardano is an example of a blockchain that uses Proof of Stake.

New York University

* Cardano Settlement Layer
* Cardano Computational Layer
* Proof of Stake Protocol
* Ouroboros
* Social Elements of Cryptocurrencies
* Simon Scripting Language
* KMZ Sidechains
* User Issued Assets
* Plutus
* Smart Contracts

Key Cardano Terms

Consensus Protocols

Hoskinson, Charles. (2017). Why Cardano. https://why.cardano.org/

Why Cardano

Cardano separates the accounting of value from the story behind why a value was moved. This is to avoid bias in execution order.

Cardano Settlement Layer

Contains the information on why transactions have occurred. This layer supports smart contracts.

Cardano Computation Layer

Proof of Stake Protocol

Ouroboros is Cardano's specific proof of stake protocol.
Cardano tested the protocol Ouroboros by having expert developers implement and test the protocol. More work was needed, leading to protocol Ouroboros Praos being created. Although time consuming and costly, revising protocols like this is important to make sure it will last for decades. 

Ouroboros

Different cryptocurrencies each have their own following and market capitalizations, yet they are built from the technologies. This points to how a large part of the value of a cryptocurrency is derived from its community. For a cryptocurrency to change in a productive way, its users should understand the social contract behind their protocol.

Social Elements of Cryptocurrencies

This is the scripting language used by Cardano. It was inspired by ideas from Simon Peyton Jones.

Simon Scripting Language

KMZ Sidechains allow for secure and non-interactive movement of funds from the Cardano Settlement Layer to any Cardano Computation Layer or any other blockchain that supports KMZ Sidechains.

KMZ Sidechains

Assets created by users that piggyback off the protocol of the blockchain

User Issued Assets

Smart contracts are self-executing programs that are coded with the terms of agreement between a buyer and a seller. They run when predetermined conditions are fulfilled. Smart contracts automate transactions to meet two main goals: reducing time loss and participant involvement. 


Smart contracts

A programming platform used for writing functional smart contracts on the Cardano blockchain. Based on the Haskell programming language.

Plutus

Staking allows user to earn passive income on their Cardano while verifying the blockchain. Moreover, the low gas fees is why Cardano is an attractive blockchain currency compared to others.

Staking Cardano and Gas Fees

Transactions are grouped into blocks and the system works to make the block's hash contain a certain number of leading zero bits. Once a proof-of-work is completed, a block cannot be changed unless the work is redone. As more blocks are added to the chain, changing the block would require redoing the work for all the following blocks too. A result of this system is that the network accepts the longest chain as the legitimate chain.

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