gosg.slide

Bla bla bla blockchain bla bla bla
Why blockchain should be part of your toolkit
26 Nov 2020
Tags: Ethereum, Solidity, Smart Contracts, Golang, Gophercon India 

Dave Appleton
Blockchain consultant
calistralabs@gmail.com
https://sorry.af
@AppletonDave

* bla bla bla
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* My aims for being here
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- To share what excites me about the ethereum blockchain 
- To inspire some of you to consider working on blockchain projects
- To explain why being a go developer puts you in a special place



* Todays Agenda
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- Introduction (me)
- The Blockchain in five minutes
- ethereum and smart Contracts
- The go-ethereum code base
- Native Dapp bindings for smart contracts
- What is ethereum used for today?


* Introduction (me)
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- Englishman living in Southeast Asia for 38 years
- Programming since 1968
- background in instrumentation, machine vision
- Blockchain dev since 2014
- Blockchain Consultant

* The blockchain in five minutes
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* What is a blockchain ?
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- signed transactions
- Put into signed blocks
- Which are added to a chain (list) by signed links
- which is distributed all over a decentralised network
- in a manner such that all the independant nodes that operate the network agree the whole thing to be valid (consensus)

* Transactions ?
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- Anything that can change the state of something.
- A transfer of value or data

    {
       From : Dave
       To : Alice
       Value : 100
       Data : "Happy Birthday Alice. Buy yourself something nice"
    }

Web analogy:

.code demo_code.txt /start REST OMIT/,/end REST OMIT/

Current state = sum of all previous transactions

* Thought of the day....
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"Young man, in mathematics you don't understand things. You just get used to them."

.caption John von Neumann.

* Digital Signatures
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- a small change in the content causes a huge change in the result.
.play hashBaby.go  /start main OMIT/,/end main OMIT/

If we encrypt the hash value using public key encryption 

we can prove it was from me 

and make it unforgeable

* Public Key encryption (WRT signing) in 20 seconds
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- create a truly random a private key
- public key (address) derived from private key
- you can derive the signer from the encrypted data and the original

means that

- encrypting the hash, ensures that the hash, thus the document is unchanged
- and ensures that the signer is who they say they are.

.code demo_code.txt /start RESTx OMIT/,/end RESTx OMIT/

* signing
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* Into blocks
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* In a manner that everybody agrees (Consensus)
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- the details are not terribly relevent in our context except
- design of consensus algorithm ensures that no one node makes all the decisions
- all the nodes get to agree on all but the most recent history
- recent history gets agreed on pretty quickly
- makes it virtually impossible for anybody to modify the past records in the chain
- means that each node has an identical copy of the state of the blockchain

* Etherscan
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- have a look at https://etherscan.io 
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* Etherscan
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- the Google of the blockchain

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* What makes Ethereum special ?
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* Introducing Smart Contracts
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- remember the "data" field?
- a way to give certain blocks of byte code an address...
- compilers
- byte-codes
- virtual machines....
- function routing...
- state variables...
Running on thousands of nodes

* What are smart contracts
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Sending data in a specific format gets it deployed to the blockchain
 as code and given an address

* Interacting with the contract
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Sending a transaction to a contract's address with correctly formatted data causes you to interact with the contract

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* interacting with the contract
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Data can be read from the contract in two ways

- calling read only functions
- coding events to log data

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* so why is this important ?
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- Everybody is building proprietary systems that interact via APIs
- If anything goes wrong at the point of interaction, who is right?
- what happens if the API has bugs?
- how do we eliminate "trusted third parties" yet remain accountable?

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* How the ethereum blockchain can help
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* Why would we do this?
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- We would have an indisputable record of interactions between systems
- Everything would be transparent and permanent (privacy options exist)
- There is a precise point of arbitration

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* OK - so where does GO come in?
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- the reference ethereum client is written in GO
- designed to allow linking into codebase
- easy to code transactions
- results in a framework to allow our servers to access the blockchain

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* and the code is soooo readable
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Not only is it Go, it is well written go

* What a smart contract looks like
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https://remix.ethereum.org

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* Well that was fun but what has that to do with Go?
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* With the de-facto ethereum client written in go
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- You can interact a low level (analysis of logs)

  for _, log := range logs {
    address := common.BytesToAddress(log.Data[12:32])
    count, _ := strconv.ParseInt(common.Bytes2Hex(log.Data[32:]), 16, 64)
    fmt.Println(log.BlockNumber, " : Thump(", address.Hex(), ",", count, ")")
  }

- or a higher level with ABIGEN binding your contract

.code go/gopherconRead/gopherconRead.go /start OMIT/,/end OMIT/

* Viewing past events using ABIGEN 
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.play go/gopherconRead/gopherconRead.go /long OMIT/,/end OMIT/


* Reading the contract's status using ABIGEN 
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.play go/reader/reader.go /start OMIT/,/end OMIT/

* Sending a transaction to the contract using ABIGEN 
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.play go/hitMe/hitme.go /start OMIT/,/end OMIT/
:-)


* Simulated Backend
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- Connect to a local one-step blockchain - i.e a chain with no history
- excellent for testing purposes (a lot faster)

.code go/simulateandtest/test.go /startClient OMIT/,/endClient OMIT/

- uses the same back EVM as geth

* Summary
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- There is a niche for go programmers in the ethereum space
- You will have a toolset unmatched by the main group of programmers
- Your lives will never be the same again