# Blockchains Study Group

**URL:** <https://forum.openzeppelin.com/t/blockchains-study-group/1647>\
**Category:** General\
**Tags:** studygroup, blockchains\
**Created:** [October 28, 2019, 3:39pm UTC](https://forum.openzeppelin.com/t/blockchains-study-group/1647 "2019-10-28T15:39:54Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![elopio](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/elopio/32/4037_2.png) [@elopio](https://forum.openzeppelin.com/u/elopio)\
**Post date:** [October 28, 2019, 3:39pm UTC](https://forum.openzeppelin.com/t/blockchains-study-group/1647/1 "2019-10-28T15:39:54Z")

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![cover_forum_blockchains-study](https://us1.discourse-cdn.com/flex022/uploads/zeppelin/original/2X/4/4055d7bb6140868dbb951fa2d5f9e86b25959986.png)

## Overview

At OpenZeppelin we have learned many topics related to blockchains, and we continue to learn more with every audit we perform. We now want to organize and publish these learnings, and to invite our community to join us on this [NeverEnding Story](https://www.youtube.com/watch?v=O5HQ1sZseKg).

This will be similar to our series [The crypto in cryptocurrencies](https://forum.openzeppelin.com/t/the-crypto-in-cryptocurrencies-and-beyond/1107) (also in a NeverEnding progress).  
We welcome you to follow along, suggest topics and contribute wherever you can.

## Structure

- Each post will focus on one core concept.
- The intended audience has no previous blockchain training. Prerequisites should be listed explicitly.
- Linking to good resources instead of reinventing the wheel is encouraged.
- All posts (including this one) are wiki posts, so they can be edited by anyone.

## Table of Concepts / Upcoming Topics

- CAP Theorem
- [The Byzantine Generals Problem](https://forum.openzeppelin.com/t/the-byzantine-generals-problem/1652)
- Practical Byzantine Fault Tolerance
- [Classification of blockchains](https://forum.openzeppelin.com/t/classification-of-blockchains/1648)
- Blockchains
  - Bitcoin
  - Ethereum 1
  - Ethereum 2
  - [Polkadot](https://forum.openzeppelin.com/t/polkadot-in-progress/1818) (in progress)
  - Telegram Open Network
  - Filecoin
  - Celo
  - Libra

- [Proof-of-Work](https://forum.openzeppelin.com/t/proof-of-work/1759)
- [Proof-of-Stake](https://forum.openzeppelin.com/t/proof-of-stake/3106)
  - HotStuff

- [Proof-of-Authority](https://forum.openzeppelin.com/t/proof-of-authority/3577)
- Finality Gadgets
- Sharding
- Distributed Hash Tables
- Erasure codes
- Gossip protocol
- Attacks
  - [51% attack](https://www.binance.vision/security/what-is-a-51-percent-attack) (external link to Binance Academy)
  - Long-range attacks
  - Eclipse attacks
  - Nothing-at-stake attacks
  - Grinding attacks

- [List of known vulnerabilities in blockchain nodes](https://forum.openzeppelin.com/t/awesome-blockchain-security/1755)

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**Author:** ![abcoathup](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/abcoathup/32/415_2.png) [@abcoathup](https://forum.openzeppelin.com/u/abcoathup)\
**Post date:** [November 4, 2019, 11:00pm UTC](https://forum.openzeppelin.com/t/blockchains-study-group/1647/2 "2019-11-04T23:00:28Z")

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Hi @elopio,

I would like to see Libra covered in the list of Blockchains.  
I would also like Proof-of-Authority in the list of consensus mechanisms.

Or should I edit the wiki directly?

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<div class="post-metadata">

**Author:** ![elopio](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/elopio/32/4037_2.png) [@elopio](https://forum.openzeppelin.com/u/elopio)\
**Post date:** [November 4, 2019, 11:03pm UTC](https://forum.openzeppelin.com/t/blockchains-study-group/1647/3 "2019-11-04T23:03:10Z")

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Go ahead and edit it @abcoathup.

I don’t want to write about Libra, but if somebody else takes the bullet it fits nicely into the study group.