Web3.0, Blockchain and Dapps

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We have already entered the era of Web3.0, which is the next evolution of the internet…. Wait! Web3.0? Are you serious? Why can we not have just a single web? What’s the matter with these different versions of the web? Oh wait, I got it! It’s all about breaking the monotonous “Web” into different versions just to sound cool, yeah?

Well, I wouldn’t deny the fact that, yes, it indeed “sounds cool”, but there is a whole story behind it…. want to know about why there have been different versions of the web and what makes web3.0 the buzzword in the community? Well, ride with me to explore this journey ahead.

  • Introduction

Web 1.0 vs Web 2.0 vs Web 3.0. We all understand the hype about Web… | by Nazhim Kalam | Enlear Academy

Do you like to create content? Writing articles, blogs and sharing information to show it to people surfing over the internet… well this was what Web1.0 was all about. Coined by Tim Berners Lee, it only had static pages in order to serve the content created by the users, the time between 1991 and 2004, when there were only a few who created the content and the rest of the people used to watch that over the internet.

Then came Web2.0, which we have been using, increased the interactivity of the users by not just providing them with the content but enabling them to interact with each other over the internet. Do you want food and groceries to be delivered to your place, want to book a ride for going out, or would you like to get feedback on your service…? Well this phase of the web addresses all these questions and provides solutions for them.

Now let me come back to where I dropped off… We have already entered the “Era of Web3.0”, which is the next evolution of the internet, that is based on openness (which means a small group of the organization will not control the content and the code but on open source platforms – means anyone, from anywhere in the world, who will be having the access to the internet will be able to use the same) and decentralization (means no permission will be needed from a central authority for posting anything on web and users will be able to interact with the services without the authorization from central authority).

As a result, Web 3.0 applications will run on the blockchain, and such decentralized apps are referred to as dApps (discussed later below). It will even use machine learning to effectively use the data, giving valuable insights to the companies and fruitful results to the consumers but it doesn’t just stop here. The application of Virtual Reality is also immense, where people can be exposed to virtual environments in various domains such as military, sports, medical, just to name a few, before they go into the real world.

  • Blockchain

Blockchain Technology Explained and What It Could Mean for the Caribbean - Caribbean Development Trends

The heart of Web3.0, blockchain, is a distributed database or ledger that is shared among the nodes (nodes are the devices or computers that participate in a blockchain network and continuously exchange the newest information or the transaction on the blockchain) of a computer network.

The first decentralized blockchain was conceptualized by a person (or group of people) known as Satoshi Nakamoto, who is known as Bitcoin’s pseudonymous creator. In a research paper introducing the digital currency, he (they) referred to it as “a new electronic cash system that’s fully peer-to-peer, with no trusted third party.” After this event, there was no going back.

As a database, a blockchain stores information electronically in digital format. Compared to a normal database, which usually stores data in the form of tables (for a simpler explanation of database, we can consider Excel sheets – as they have the data organized in the form of rows and columns), blockchain structures its data into blocks, that records the data, and distributes it over the network of nodes but do not allow it to be edited. In this way, a blockchain is the foundation for immutable ledgers, or records of transactions that cannot be altered, deleted, or destroyed.

Distributing the data among several network nodes at various locations, not only creates redundancy (means multiple copies of the same data available all over the network) but also maintains the fidelity of the data stored therein—if somebody tries to alter a record at one instance of the database, the other nodes would not be altered and thus would prevent a bad actor from doing so.

If one user tampers with a record of transactions, then, all other nodes would cross-reference each other and easily pinpoint the node with the incorrect information. This system helps to establish an exact and transparent order of events. This way, no single node within the network can alter information held within it.

Web3.0, Blockchain and Dapps

Because of this, the information and history of the data stored on the blockchain are irreversible. Blockchain can find its applications in various places such as in:

  • Secure sharing of medical data
  • NFT (non-fungible token) marketplace
  • Cross-borderer payments
  • Supply chain and logistics monitoring
  • Anti-money laundering tracking system
  • Voting mechanism
  • Crypto exchanges
  • Secure IoT (internet of things) network

  • Dapps

What Are dApps?

Decentralized applications (dApps) are digital applications or programs that exist and run on a blockchain or network of computers directly connected with each other on the network (P2P or peer-to-peer network) instead of a single computer. These are outside the purview and control of a single authority.

Well, this was somewhat a broader definition, and to understand it better, let’s understand it through an example…

A standard web app, such as Ola, Uber, Twitter, Amazon, etc, runs on a computer system that is owned and operated by an organization, giving it full authority over the app and its workings. There may be multiple users using the app on one side, but the backend is controlled by a single organization. DApps can run on a P2P network or a blockchain network.

Web3.0, Blockchain and Dapps

A peer-to-peer (P2P) service is a decentralized platform whereby two individuals interact directly with each other, without intermediation by a third party. Here the buyer and the seller directly communicate with each other without the involvement of another party or organization between them. Also, as it runs on a blockchain network, hence whatever data once registered on it, cannot be deleted by anyone.

dApps use smart contracts (these are basically a piece of code which are embedded inside the block of a blockchain, in order to carry out computations and transactions, like Ethereum blockchain uses Solidity language to write, store and run codes inside its block) to complete the transaction between two anonymous parties without the need to rely on a central authority.

A smart contract is a self-executing contract with the terms of the agreement between buyer and seller being directly written into lines of code.

Web3.0, Blockchain and Dapps

Ethereum dApps use smart contracts for their logic. They are deployed on the Ethereum network and use the platform’s blockchain for data storage. Ethereum provides flexible dApps development, hence helping in the rapid deployment of dApps for a variety of industries including banking and finance, gaming, social media, online shopping, and many more.

  •  Conclusion

We can finally see the story behind the different versions of the Web and how the blockchain and decentralization have already been bringing the revolution in the tech domain. The digital world is changing rapidly, and companies need to keep up with the swiftly moving tech environment. Along with the survival of the fittest, it’s also about the survival of the swiftest! You can beat your competition in the market if your company not only adapts to modern technology but if it’s also able to adjust itself to the modern environment faster than the others.

Blockchain and Security Blog Series

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This Blog Series is meant for everyone willing to grab a look underhood the Blockchain and Security system. Doesn’t matter you are a freshman or a senior, do a diligent reading and try to comprehend whatever is written.

This is especially to show a “Road not Taken” usually by the undergrads of the college. Hope this insight helps!!!

In case of any query, shoot an email to aman0902pandey(@)gmail.com

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Day01 – “Why?” & “What in?” Security & Blockchain?

author: aman Blog I – Part I – Day 01 Hey guys, I was just sitting an thinking to what else can be initiated in CEV, as an attempt to show my college people something “Cutting-Edge” and that can actually share with the undergrads here, to what is called as “The Road not taken!” With that I came up with a thought to start a series of micro-blogs on “Why?”…

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Day03 – “Why?” & “What in?” Security & Blockchain?

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Day04 – “Why?” & “What in?” Security & Blockchain?

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Day07 – “Why?” & “What in?” Security & Blockchain?

Blockchain is often described as merely the technology behind the “Cryptocurrencies” and people fail to perceive the avenues it opens for the greater good of mankind. In reality, Blockchain is to cryptocurrency as to what the Internet is to email.  You never thought about applying blockchain in different domains for the upliftment of the society because you were too busy trading in Bitcoins and ether to mint money since that’s…

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Day08 – “Why?” & “What in?” Security & Blockchain?

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Day11 – “Why?” & “What in?” Security & Blockchain?

author: aman Blog III – Part I – Day 11 Hope the blogs are going pretty well. In this very blog, divided into several micro-blogs, I’ll be explaining about the Hyperproperties. This particular thing will take you to the most obvious level of understanding the computer systems. And in this particular micro-blog, I’ll tell about hyperproperties, directly. Most of the work will be taken from the teachings of my mentor…

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Day12 – “Why?” & “What in?” Security & Blockchain?

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Day13 – “Why?” & “What in?” Security & Blockchain?

author: aman Blog III – Part III – Day 13 Understanding Hyperproperties and Blockchain together. And how this could be so big! Let’s get in…. In this micro-blog Let us check this vaguely 2-trace property Hyperproperties Safety and Liveness – Another 2 very Important terms Blockchain & Hyperproperties How this could be so big? Safety and Liveness – Another 2 very Important terms As already explained, Property is a set…

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Day14 – “Why?” & “What in?” Security & Blockchain?

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Day15 – “Why?” & “What in?” Security & Blockchain?

author: aman Blog IV – Part II – Day 15 Let us get some dirty hands on with some more Solidity code and exploit a few more Ethereum – Solidity bugs. Here we’ll discuss about the famous DAO attack, caused by the reentrancy bug. Let us do it… In this micro-blog delegatecall (the proxy calls) (SWC-112) (Inclusion of Functionality from Untrusted Control Sphere) DoS With Block Gas Limit (SWC –…

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Day16 – “Why?” & “What in?” Security & Blockchain?

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Day17 – “Why?” & “What in?” Security & Blockchain?

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Day18 – “Why?” & “What in?” Security & Blockchain?

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Day19 – “Why?” & “What in?” Security & Blockchain?

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Day20 – “Why?” & “What in?” Security & Blockchain?

author: amanBlog VIII – Part I – Day 20Hey there, Sorry for time being away. In the complete series the main focus was to get the undergrads of my college to a kind of “ROAD” that is not taken “usually”. This was something out of the world of Competitive Coding and Machine Learning. Since the Internet is Changing, and Blockchains are the one who is the Lead Changer of this…

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Aman Pandey (BTech III)
Kaushik Chandra (MSc Physics I)
Gaurav Kumar (BTech I – ECE)

Squashing the Key Concepts related to Hyperledger Fabric

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Squashing the Key Concepts related to Hyperledger Fabric

Indeed you are at the right place 💖

I assume you already know about the key concepts of DLTs before you start reading this blog. If this is the case, let’s know more about Hyperledger Fabric.

What is Hyperledger Fabric and does it suits your use-case or application?

Hyperledger Fabric is a private and permissioned 🔐 DLT or a Blockchain to be precise, which comes under the umbrella of Linux Foundation.

As it is permissioned, one can not join or leave the network at any time. The members 👨 of a Hyperledger Fabric network enrol through a trusted Membership Service Provider (MSP), which we will discuss later.

The reason why it gains a mass adoption in Blockchain Marketplace is its modularity & flexibility. It allows to plug in different consensus algorithms, different database to save the data in ledger, and even allow to use different MSP to enrol users.

Hence, if you are looking for a Modular Permissioned-Blockchain Enterprise solution, Fabric can be the choice which you will definitely like.

Architectural Components of Fabric:

Like any permissioned blockchain network, Hyperledger Fabric has various actors & components like orders, peers, client applications, MSPs, CAs, etc. Let’s discuss them one by one.

1. Membership Service Provider:

Any of the actor 👨 in Fabric has an identity & according to the identity, the exact permissions and role of the actor are decided. So, from where do these identities come from and who decide the permissions? Yes, the MSP is the entity that defines rules, permissions and roles of different actors, whose identities have been issued by a valid CA(Certificate Authority).
The documentation says:

MSPs turn verifiable identities issued by CAs into the members of a blockchain network.

Summing up, an MSP abstracts away the protocols behind issuing certificates, validating certificates, and user authentication with all the cryptographic mechanisms, handled by CAs.

Note: Fabric comes with a built-in CA component, called Fabric-CA to allow you to create CA on the blockchain network. However, this component is pluggable and you still have to options to choose from other available CAs.

2. Peers
A peer is a node that hosts instances of the ledger and chaincode in the blockchain network. So, if an application or an admin wants to query the ledger or update the ledger then a connection with a peer is required.

A peer in the fabric network can hold more than one ledgers, which can be governed by one or more chaincodes.



A peer hosting multiple ledgers. Peers host one or more ledgers, and each ledger has zero or more chaincodes that apply to them. In this example, we can see that the peer P1 hosts ledgers L1 and L2. Ledger L1 is accessed using chaincode S1. Ledger L2 on the other hand can be accessed using chaincodes S1 and S2.

3. Orderer

An orderer node packages the transactions into a block 📦, which is then sent to peers, and after verification ✔️ appended to the ledger.

In a fabric network, there are various provisions for the configuration of orderer nodes. We can use a single orderer node (SOLO, deprecated from v2.0) or also a group of orderer nodes can be used to order the transaction and form a block, and this forms an ordering service.

As Fabric is a permissioned blockchain, and real message passing can take place between the nodes, so it doesn’t depend on probabilistic consensus algorithm for ordering of transactions like in the case of Bitcoin and Ethereum. So, all you have to do is to use the consensus algorithm provided by fabric, or you can plug in your own implementation.

4. Channel

Channel provides a mechanism for the peer to communicate & transact privately. Conceptually, each of the ledger in the network is associated with a channel and the peers which have joined the channel can view and transact on that ledger only.

Squashing the Key Concepts related to Hyperledger Fabric

In the above case, three channels C1, C2 &C3 exists, conceptually shown by black, blue, & orange rectangle. Peer P1 & P3 have joined blue channel(C2) and black channel(C1) and P2 & P4 have joined the orange channel(C3) and black channel(C1). So, the Blue ledger is maintained by P1 and P3, whereas Orange Ledger is maintained by P2 and P4, but black ledger is maintained by P1, P2, P3 and P4.

Here is another reference from Fabric’s Documentation:

Squashing the Key Concepts related to Hyperledger Fabric

P1 & P2 have joined channel C1 and thus can access the ledger L1. P2 & P3 have joined channel C2, thus can access ledger L2. The interesting part is peer P2 have joined both the channels, thus can access both the ledgers.

5. Ledger

Fabric’s Ledger 📒 is a distributed database with two components –

World State — the state of the ledger at a given point in time. So, world state stores the most recent value of assets in the form of key-value pairs.
Transaction Log — records all transactions which have resulted in the current value of the world state; it’s the update history for the world state.

A Ledger L comprises blockchain B and world state W, where blockchain B determines world state W. We can also say that world state W is derived from blockchain B.

A Simple Transaction:

Whenever a transaction is performed, it modifies the world state and the record of the transaction is made in the log of the ledger.

Squashing the Key Concepts related to Hyperledger Fabric


  • In Fabric, the database associated with the world state is pluggable and comes with two choices LevelDB & CouchDB.
  • Transaction log doesn’t need to be pluggable.

6.Smart Contract & Chaincode

Smart Contracts are the codes that contain the business logic in the fabric-network. It defines the business cycle of an asset in the world state. So the business logic inside the smart contracts governs all the transactions.

Here is a pseudo-code smart contract from the documentation:

Squashing the Key Concepts related to Hyperledger Fabric

Smart Contract ‘Car’ 🚗 defines the business logic to query, transfer and update the ownership of the car, agreed upon by Org1 & Org2

Smart Contracts are packaged into the Chaincode for deployment on the blockchain-network.

Think of smart contracts as governing transactions, whereas chaincode governs how smart contracts are packaged for deployment.

There are also some chaincodes which work on lower-level, to perform the necessary tasks in the blockchain-network, and they are called system chaincodes.

It is better to cover the chaincodes & transaction life-cycle in a different blog, later on 😺.

Squashing the Key Concepts related to Hyperledger Fabric

So that’s it. Thanks for reading.

Official Docs: https://hyperledger-fabric.readthedocs.io/en/release-2.1/

If you are facing difficulties in setting up Hyperledger Fabric, refer:

Hyperledger Fabric v2.1: Setting Things Up


Day20 – “Why?” & “What in?” Security & Blockchain?

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author: aman

Blog VIII - Part I - Day 20

Hey there, Sorry for time being away.

In the complete series the main focus was to get the undergrads of my college to a kind of "ROAD" that is not taken "usually". This was something out of the world of Competitive Coding and Machine Learning. Since the Internet is Changing, and Blockchains are the one who is the Lead Changer of this internet revolution. I guess, transformation would be the right word.

We have discussed about a lot of things, let's put them together.

In this micro-blog

  • Connecting the Dots
Connecting the Dots

So, we've talked about a lot of things in the series of the Blogs. However, I must say that I couldn't cover everything I knew in detail, but here I'll try to connect the dots for you.

Let me list the blogs with the topics they covered. (You are free to skip through the list, just come back if you want to grab a look at what has been already done.)

We talked about various sotware attacks, attacks on Blockchains, how terminologies(soundness, completeness) could mean so much, vulnerabilities, specs/invariants, bugs in few of the most trusted spaces. We also had 2 guest lectures in the series. Let me now end up with a complex case in case of Bitcoin.

The case leaves a possibility for an attacker to Partiotion the Bitcoin network into multiple parts, creating a possibility to fork bitcoin into 2 parallel chains. Let's see how it works:

BGP Highjacking attack on Bitcoin

The Bitcoin network is highly centralised, even after known to be a decentralised network. And even if the Blockchain is completely encrypted the routing of messages is still very much open. The routes are easily deductible to the adversaries.

See Here : https://bitnodes.io/

To explain it more, the complete Bitcoin network is spread to multiple ISPs (Internet Service Providers), which are again built up of multiple network clusters, called as Autonomous Systems(ASes). To communicate some messages between these ASes uses a protocol called the Border Gateway Protocol(BGP). This complete complete procedure is termed as Internet Routing.

~13 ASes host about 30% of the entire network, while 50 ASes host the 50% of the Bitcoin Network

Any attacker with accesss to the routing infra, can Highjack the BTC network. As a result of attacking mentality they can partition the BTC network in several parts. Probably bringing a major network towards their side.

Now they can add as many blocks in their side, and broadcast the chain in the network. By the general rule of Bitcoin network, "the longest chain is considered to be the final chain", the malicious one gets updated in the real etwork.

"hese attacks, commonly referred to as BGP hijacks, involve getting a router to falsely announce that it has a better route to some IP prefix."

"50% of Bitcoin mining power is hosted in only 39 prefixes (i.e., in 0.007% of all Internet prefixes). This allows an attacker to isolate ~50% of the mining power by hijacking only these 39 prefixes. Much larger BGP hijacks (involving orders of magnitude more IP prefixes) are routinely seen in the Internet today."

You see this is a big thing. The Internet Routing has a developing history of more than 35 years, and the BGPs are still considered to be stable. It is said that, Bitcoin has already gone through hundreds of BGP routing attacks, and the attacks are still not deductible.

So turning back and seeing the dots to be connected, we find,

  • a 100% secure system isn't possible
  • not a lot of people are aroung the security of these systems
  • the higher institutes are still hustling to create an environment of secure information exchange
  • developing techniques to check a system for its security is extremely difficult, and this is the place where actual computer science comes in
  • the attack surfaces are open in Hardware devices as well,
  • the Finance field is already being exploited for its vulnerabilities and application for the Blockchain tech

One thing to notice is that, even if the Blockchain tech fails, there will be a definite transformation in the internet we will be using tomorrow.

The security is everything. For a world running on Data, User's privacy, access to the systems comes in first.

So, that should be a lot of motivation I guess. I don't have any pre compiled list of the things, one can work on in the future, but BLOCKCHAIN + SECURITY, is surely the most citable area of work.

I'll try to cover more in details sometime. And yeap, I never read the Blogs twice, so pardon for the errors.

Shoot your questions and error reporting here aman0902pandey@gmail.com.

- Aman Pandey


Hyperledger Fabric v2.1: Setting Things Up

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This article will take you to the easy steps for setting up Hyperledger Fabric v 2.1. It will be in reference to the Hyperledger Fabric Official Documentation, with short explanations at each & every step to save your time. I have seen, there are small-small things which people usually miss while setting up a fabric-network and face a lot of difficulties because of choosing the wrong version of dependencies, exporting wrong paths and many more things. So, my main motive to write this blog is to see you running the test-network, without missing anything.


* I will be using a Ubuntu 18.04 VM, on GCP for setting up the test-network.

Aye Aye Captain!! 🚢, let’s sail…

Installing the Pre-requisites & Getting the fabric binaries:

Just keep following the steps with me 😉:

  • Install curl, docker, docker-compose, nodejs & npm.
sudo apt install curl docker docker-compose nodejs npm

2. Install golang

Don’t install golang using apt, because ubuntu generally maintains an older version of golang 😕. Use official website of golang to download it, and follow me:

a)Use curl or wget to download the current binary for Go from the official download page:

wget https://dl.google.com/go/go1.14.2.linux-amd64.tar.gz

b)Extract the tarball

tar -xvf go1.14.2.linux-amd64.tar.gz

c)Adjust the permissions and move the go directory to /usr/local:

sudo chown -R root:root ./go
sudo mv go /usr/local

d)Adjust the Path Variables in .bashrc

export GOPATH=$HOME/go
export PATH=$PATH:/usr/local/go/bin:$GOPATH/bin

e) Load the file commands into the current shell instance

source ~/.bashrc

Note: Always check the minimum-version of any of the pre-requisites to avoid hustle.

3. Enable docker to run on

sudo systemctl enable docker

4. Add you, user, to the docker group

sudo usermod -a -G docker <username>

5. Install Fabric binaries

curl -sSL https://bit.ly/2ysbOFE | bash -s

6. Export path to your download location of fabric samples

export PATH=<path to download location>/bin:$PATH

You can see the following docker images pulled in your system now, by using

docker images

Hyperledger Fabric v2.1: Setting Things Up

Okay, after all this you are now in stage to test the first-network example provided by hyperledger fabric.

Hyperledger Fabric v2.1: Setting Things Up

Playing with the Fabric test-network bed:

To begin, change the current directory to the test-network folder and let’s move on.

Make sure there is no container related to Hyperledger Fabric is running before proceeding. Use these commands to stop them:

./network.sh down


docker rm $(docker ps -aq)

Architecture of test-network:

The test-network which comes with Fabric v2.1 contains 2 Organizations with 1 Peer each and an Orderer organization with 1 peer.

You can see the ccp-generate.sh for knowing configurations related to orgs.

Hyperledger Fabric v2.1: Setting Things Up

Also, configuration required to generate the crypto materials for peers and orders is present in yaml files in cryptogen folder.

Check out some snaps 📷 from crypto-config-org1.yaml file from the cryptogen folder:

Hyperledger Fabric v2.1: Setting Things Up

Hyperledger Fabric v2.1: Setting Things Up

You can see the Template Count set to 1. It corresponds to the fact that only one peer will be created for the org, and crypto material is generated for that only.

Let’s move to the demo in just three steps:

Step 1: Bringing up the test-network

./network.sh up

If everything completes smoothly, then you will be able to see the following three containers- two peers & one orderer.

Hyperledger Fabric v2.1: Setting Things Up

So what actually happened in the previous command, the answer lies in the network.sh.

Hyperledger Fabric v2.1: Setting Things Up

The command ./network.sh up itself calls two functions to create orgs and create consortium.

Hyperledger Fabric v2.1: Setting Things Up


You can see that cryptogen is using the config files residing in organisations folder.

Note: One good enhancement in the test-network in v2.1 is that it also has an option to create identities using fabric-ca. Earlier version created the identities and crypto materials using cryptogen tool. So now it’s on you to choose the fabric-ca or cryptogen to generate the cryptographic materials for orgs. And, as matter fact Fabric doesn’t care at all about from where does the identities/certificates came. It just use them form verification and signing.

Similarly, the code to create org2 and orderer using config files from organisation folder is also present in the same function.

On the very next step, the createConsortium function will create a genesis block in the orderer system channel.

Hyperledger Fabric v2.1: Setting Things Up

That’s all you have all the necessary containers up at this stage and we can move on the next step to create a channel for transactions between Org1 and Org2.

Step2: Creating a channel

The createChannel() function in network.sh will use createChannel.sh script residing in the scripts folder.

Take a look at the script and you will find, it performs the necessary tasks like updating the anchor peers, creating channel and making the peers to join the channel.

So let’s fire the function using:

./network.sh createChannel

Whoops, you are one step closer to test the network.

Okay, so the last step is to deploy the chaincode on the peers corresponding to the channel which you have just created.

Step3: Deploying the ChainCode

./network.sh deployCC

Check out the script deployCC.sh. It packages, install and instantiate the chaincode on peers.

We will discuss the chaincode structure in a separate blog. Hope I will write it soon 👯 .

Now you are free to interact with chaincodes. But…

Hyperledger Fabric v2.1: Setting Things Up

From Fabric v2.0, Docker daemon dependency has been eliminated. So, now you can directly use the peer CLI to interact with your network.

To interact first with the peer CLI make sure:

  • You have exported the path to fabric binaries, which I think we have already covered in Pre-requisites steps.
  • Export the path to config folder in fabric-samples.
export FABRIC_CFG_PATH=$HOME/fabric-samples/config/

After that you are ready to go, you just need to export environment variables for Org1, if you want to use that.

export CORE_PEER_TLS_ROOTCERT_FILE=${PWD}/organizations/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt
export CORE_PEER_MSPCONFIGPATH=${PWD}/organizations/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp
export CORE_PEER_ADDRESS=localhost:7051

After that, you are ready to go to interact with the chaincode installed on the peer.

So, let’s try the query command:

peer chaincode query -C mychannel -n fabcar -c ‘{“Args”:[“queryAllCars”]}’

Similarly, you can invoke other methods of chaincode.

You can also use some other chaincode residing in the chaincode folder of fabric-samples by modifying the deployCC script, or even you can test your own chaincode on the test-network.

Celebrate, you are now aware of managing a Hyperledger Fabric simple network and taking the reference of this test-network, you can design your own network and feel like a Blockchain Architect.

Feel free to discuss some of the errors you may encounter while setting up the network, in the comments.

I’m leaving my bash.rc important exports in case you missed something:

export GOPATH=$HOME/go
export PATH=$PATH:/usr/local/go/bin:$GOPATH/bin
export PATH=$HOME/fabric-samples/bin:$PATH
export PATH=$PATH:$GOPATH/bin
export FABRIC_CFG_PATH=$HOME/fabric-samples/config/

Don’t forget to clap, if this blog saved your time 👏 👏 👏

Hyperledger Fabric v2.1: Setting Things Up


Day19 – “Why?” & “What in?” Security & Blockchain?

Reading Time: 4 minutes

author: aman

Blog VII - Part I - Day 19

So, towards an end of this series.

I was quite busy in some other blog so couldn't write this one quickly.

In this blog I'll take up a case of a Security tool used in Ethereum Smart Contract bug discovery, ECHIDNA. I'll try to unwrap a few things about how a security can be used to analyse a "script", that governs the business of an organistion over Blockchain network. I'll try to cover almost everything taught last time in these 2 upcoming micro-blogs.

Let's take a look what's coming up...

In this micro-blog

  • One thing you can't believe in...
  • Fuzzer
  • Echidna
  • the Trail
One thing you can't believe in...

You might be having this strong image of BLOCKCHAIN, that a fraudulent transaction in a Blockchain cannot be reversed. Well...what is I say, it is actually inaccurate.

One of the famous article in MIT Technology Review, by Mike Orcutt, titled as "Once hailed as unhackable, blockchains are now getting hacked", stated the following:

"Blockchains are particularly attractive to thieves because fraudulent transactions can’t be reversed as they can be in the traditional financial system."

The statement is actually inaccurate!

Ethereum classic is an example to it. Remember, I've told you people before about the famous DAO attack. The had a massive $50 million money heist. Well the attacker is still a mystery.

The funds stuck until July 14, 2016. See the article. The possibility of attack was due to a vulnerable smart contract, that governs the functioning of DAO.

This was the problem until the Ethereum Chain was forked, after a long debate among the community. The transaction was rewritten in the new chain and now there exists 2 ethereum chain. One, that we use now, and where the DAO attack never happened. The other one, Ethereum Classic, where the DAO attack happened.

This is a note published by Vitalik Buterin, the founder of Ethereum Blockchain.

Strange!! yeah...?

Lets try to know about something which is used as a help to "not" get into such troubles...


Prevention is better than cure! Since, every crucial thing from a developer side depends on how well the contracts are written. If the contract does not release any possibility of attack, any loopholes of information leakage, the contract is probably secure.

Just like normal computer programs, there exists this old and always alive Computer Science (we may call it fundamental though). Analysing the programs statically and in dynamic environments to detect the bugs that can be triggered or are automatically getting triggered.

There are several techniques to anlayse a program. Symbolic analysis, Dynamic Analysis, Model Checking, Fuzzing...

There had been a lot of Security Tools in development recently. Here is a sophisticated list of all, in the official listings of CONSENSYS.link

I will talk a bit about the only fuzzer system available for Smart Contract Analysis, by an Argentanian company TrailofBits. The tool is known as ECHIDNA.

Bonus excerpt(link)


day19_01 **pretty logo! isn't it?

ECHIDNA, is a property-based fuzzer system available for generating malicious inputs and break the smart contracts. It means, we write a certain property(like the one a system should "always" follow, or should "never" follow), and the system runs it on a local virtual machine, which is inbuilt with the tool. The system starts fuzzing. i.e. inputting the contract with random inputs, to check where the system fails the written property. These inputs are determined by input generation techniques, which are certainly in "possible limits" tha EVM can handle, and are not that arbitrary.

The tool is written in HASKELL, which is a FUNCTIONAL PROGRAMMING LANGUAGES, which you probably have never heard about. This means the code is short and does a lot. To give a intuitive brief, the Functional programming language are actually concerned about "What the thing is?" rather than "How the thing works?". Most of the SAT/SMT solvers, that I have talked about before are built over functional programming languages.

How ECHIDNA works? from user's point of view You write a smart contract with certain invariants(the property you think should never change and the smart contract should always follow). Then you run that within the system.

the Trail

After discussing all this... you must have got a great idea about what is actually going out around the world.

The next blog will be a very special Connect the dots... thing. Will have no technical knowledge.

I will just cover the things I & the 2 guests Kaushik & Gaurav has compiled for you people.

Will finally unveil the "The Road Not TAKEN..."


Day18 – “Why?” & “What in?” Security & Blockchain?

Reading Time: 5 minutes

Hey guys, in this Blog I will be discussing the Integration of Blockchain with IoT (Internet of Things).

So, let’s proceed with what IoT actually is.

What is Iot?

Internet of things is an environment of connected physical devices embedded in various systems and accessible on the Internet, thus rendering these devices to become autonomous and can be controlled through their digital representation. The whole idea behind IoT is based on the transfer of data between two physical devices connected over a network and thus based on these data they act, like simulating the temperature of a house as in the case of smart homes, saving your attendance in a database as in for RFID.

Some of the industries and technologies developed on IoT includes smart homes, automotive environment, Healthcare, smart cities, smart grids, smartwatches, banking sector, etc.

perks of iot:

If technology is being used in multiple industries, it is a bit obvious that it should have some edge over the rest. The benefits of IoT are:

  • Communication: As discussed, it enables Machine-to-Machine(M2M) communication over the network on which both of them are connected.
  • Automation with control: Devices are controlled over a centralized wireless infrastructure, thus enhancing automation. This brings out an efficient communication between the devices, leading to output at a greater speed.
  • Monitoring over Information: The amount of data we receive through these IoT devices is enormous and hence it can be used to monitor the efficiency of these devices as well as take the algorithmic decisions more effectively due to this huge dataset.
  • Saves Money: Optimum usage of energy and resources with proper surveillance helps in avoiding possible shutdowns (as in industries), damages or waste of resources.

Thus, the price paid for implementing these IoT devices is very minimal when compared to the benefits it provides.

problems in iot:

“With a great amount of data comes out a greater responsibility to process it safely”.

The IoT network is a centralized one and also contains a large number of devices and involves the application of a huge set of data points, which requires security. This not only expands the attack surface, and hence IoT security and IoT privacy are huge concerns.

A case of such an IoT attack that took place in 2016, in this Mirai (a Botnet) penetrated in the domain name service provider Dyn and performed a DDoS (Denial of Service Attack) for a huge period, as a result, a large number of websites were down. It was achieved as the attackers gained access to this centralized network through the poorly connected IoT devices.

With such a huge vulnerability, it becomes non-practical to implement IoT in industries, Healthcare, or Banking sector where data security and privacy is a major concern. Also, the network is centralized hence the manufacturer, who is the most probable administrator to this can gain access to data. Hacker just has to find one vulnerability to gain access to the network and he will be able to gain control over the entire network.

Blockchain to rescue!!

To extend the properties of decentralization and data encryption to IoT, Blockchain is a major technology

being looked up to. Blockchain can ensure the decentralization of the network thus greatly reducing the

chances of any attacks on the IoT devices on the network. Also, encryption can be achieved at multiple

data entry points. Some of the features that can be added to IoT with the use of Blockchain are:

  • Identity: using a common blockchain network every node can identify all the devices. Data provided to the system is immutable and holds a record of every change in it. Also, the authentication of each device becomes more secure.
  • Scalability: using a blockchain network the fault tolerance and the system scalability also improves.
  • Security: blockchain can be used to secure the data contained in the network as transactions. Here, the data transfer is treated as a transaction that follows the rules set by the Smart Contracts.
  • Autonomy: using Blockchain the interaction of devices is decentralized and hence there are no servers. This makes the deployment of smart autonomous hardware possible for the service.
  • Secure code deployment: the deployment of codes into the devices also becomes more secure with the use of Blockchain. Thus, the developer can be confident that the code running on the device is the one he wrote and not the one by some malicious attacker.

problems in the integration

It’s not very simple to merge the two mentioned technologies which were not designed to work with one another and hence almost all the features that we added above as the benefits have certain restrictions.

Blockchain was made to be operated with much accessible Internet along with a device supporting high computational power which is not a property of IoT devices. Some other problems faced while the integration of the two is:

  • Storage capacity: IoT devices produce a huge amount of data in a real-time application while the blockchains we want to implement perform only a few transactions per sec. Thus, Blockchains are not meant to store this huge amount of data.
  • Security: the security problems at different levels furthermore increase with additional complexity as a result of a large variety of devices. Blockchain ensures the immutability of the data in the chains but cannot detect if the data received is already corrupt due to some hardware failure, environment change, etc. Thus, the IoT devices to be used on the blockchain need to be checked properly to avoid any such probable cause to occur.
  • Anonymity and data privacy: IoT devices that are used in the Healthcare sector or Banking sector deal with many private details and it is important to establish trust for data privacy and anonymity. But the problem of data privacy in IoT devices is complicated than the private and public Blockchain network as it starts with the collection of data and goes up to application level. 

    Hence securing the device requires the integration of security cryptographic software’s which generally harm the resource limitations of devices and hence economic viability.
  • Smart Contracts: the killer application of blockchain technology presents many challenges to IoT technology as they do not fit in IoT applications easily. Validation of these Smart Contracts is compromised if the IoT is not stable. Also accessing multiple data sources can result in overloading these contracts.
  • Consensus: the limited resource in IoT devices makes the PoW consensus unsuitable, there are other proposed consensus mechanisms (PoS, PoU, etc) but these are still not mature enough for their implementation. The initiatives have been taken of implementing full nodes into IoT devices, mining is a big challenge in IoT due to these limitations.


The Hybrid approach, using only a part of the interactions and data takes place in the blockchain and the rest are directly shared between the IoT devices, has been used in fog computation and is being tested for application in other domains, so we can safely say that the possibilities are high. Hope things work out well between the two great technologies.

Day17 – “Why?” & “What in?” Security & Blockchain?

Reading Time: 3 minutes

author: aman

Blog V - Part II - Day 17

Hey People, I have given a gist of how the EVM stores the smart contracts on its machine.

In this I will directly discuss some technical things about, how deep you can dive into using just the information told about in the previoud micro-blog. Will try to give a glimpse, rest you can think of autonomously.

Let's do it...

In this micro-blog

  • Ethereum Virtual Machine (EVM)
  • The two Properties of EVM
  • How the Smart Contracts are actually stored?
  • Some supplementaries
  • These trail of Digits have some meaning
  • How can the attackers mis-use it?
Some supplementaries

I would suggest to open up following things in other tabs, would help you people throughout:

These trail of Digits have some meaning

I will keep this explanation as vague as possible, as we have some people onboard who have excitement about the blockchain, despite their core interests and Fields.

You know right, EVM is a Stack based machine, as 2 + 2 is actually written as 2 2 +, postfix notation.

If you break this "strange series of digits", 608060405234801561001057600080fd5b5060016000819055506......

according to as shown in ethervm.io tab.

Day17 - "Why?" & "What in?" Security & Blockchain?

EVM is a stack-based machine and for actions to happend on this machine, these trails are converted into the OPCODES.

Each OPCODE has a size of 1 byte. EVM has a set of 140 OPCODES in total

000060PUSH1 0x80
000260PUSH1 0x40
000861PUSH2 0x0010

Now, you understand how this thing works in EVM Stack? It would be infeasible to explain here how does a stack work. You better watch a video here call stacks & a big blog series here

If you are wondering how can you find the contract with that data? Well...just try copying pasting the following BYTECODE, and decompile in the ethervm.io/decompile, you'll find the same contract as was written in the previoud micro-blog simpleContract.sol.

How can the attackers mis-use it?

The level of publicity, Blockchain provides, any user can directly use the address of the contract deployed, to instatiate a variable of that, contract and call its various function.

This is not small, this can let the potential attackers exploit the contract and cause big-attacks like, DAO-Reentrancy attack, or DDoS Gas attack, explained in the previous blogs.

As I have told, these work as the fill in the blanks, the vacant spaces within the Bytecode are initiated by 0 , which is then replaced by the hexadec code of the input.

This contract is again deployed to replace the existing one, changing the current state of the contract.

The Internal checks verifies whether you are the authorised one to make a certain check or not.

IG, This concept is heavily used in off-chains, as well.


Find deeper readings here

Day16 – “Why?” & “What in?” Security & Blockchain?

Reading Time: 3 minutes

author: aman

Blog V - Part I - Day 16

Hey People, I have been a little busy for last few days. Plus it took me some time to find the correct stuff that should fir right in the series.

So now, after so many micro-blogs, it is possible that you must be wondering on How an attacker can even do this? For that I'll be giving you people an idea about what things are openly available to people, potentially an attacker, to be able to exploit the weaknesses of the blockchain governing codes.

We'll take up Smart Contracts in world's larget Decentralised Application(dAPP) platform. Ethereum works with the currency called ETHER(ETH).

I will give you a quick look into what all information is publicly available, and an idea about what all can be extracted from the information available.

Lets dive deep in...

In this micro-blog

  • Ethereum Virtual Machine (EVM)
  • The two Properties of EVM
  • How the Smart Contracts are actually stored?
Ethereum Virtual Machine (EVM)

Ethereum, is actually a large collection of machines spread across the world in decentralised fashion. And a Ledger containing the details of all the transactions is distributed across all the machines(called nodes).

Ethereum Virtual Machine or EVM, is a system used to refer to this computer.

The two properties of this EVM

1) EVM is Quasi-Turing

A turing complete machine is the one, which is able to solve any problem provided to it, despite the fact how long does it take.

EVM is quasi-Turing because, it is limited by a factor, COST. Any computation you make to it, it is limited by the gas price required to solve this problem.

2) EVM is Stack Based Machine

EVMs Data Structure is Stack Based.

for e.g. 2 + 2 can be given as 2 2 +

How the Smart Contracts are actually stored?

If still you think the contract(i.e. the governing document on the Ethereum Blockchain), is stored in the textual format, as the following one, then you are absolutely wrong.

To work on EVM, the Smart Contracts are to be converted into a specific format called, the bytecodes.

After compiling the Smart Contract into the bytecode using Solidity compiler(solc), it is exported to the EVM.

  • Contract Bytecode: is the bytecode of the complete smart contract. That is actually, what ends up staying on the EVM.

It is comprised of functions(), already initialised variables, and all that is predefined. Plus, Something that can be changed during running.

  • Runtime Bytecode: it is the same bytecode that can be changes during running.

It can be said that Contract Bytecode = (some bytecode) + (Runtime Bytecode)*

-> Now, when compiled the above smart contract will look like,

if we compile it using solc --bin simpleContract.sol, we get the Contract Bytecode

======= simpleContract.sol:SimpleStorage =======


608060405234801561001057600080fd5b5060016000819055506 0c6806100276000396000f3fe6080604052348015600f57600080 fd5b506004361060325760003560e01c806360fe47b1146037578 0636d4ce63c146062575b600080fd5b6060600480360360208110 15604b57600080fd5b81019080803590602001909291905050506 07e565b005b60686088565b604051808281526020019150506040 5180910390f35b8060008190555050565b6000805490509056fea 265627a7a723158200e135b4c7bcf7bde9dca1f257d97637d8137 b315e29248b5654ac7830dab9e8264736f6c63430005100032

and, if we compile it using solc --bin-runtime simpleContract.sol, we get the Runtime Bytecode

======= simpleContract.sol:SimpleStorage =======

Binary of the runtime part:

6080604052348015600f57600080fd5b506004361060325760 003560e01c806360fe47b11460375780636d4ce63c146062575b6 00080fd5b606060048036036020811015604b57600080fd5b8101 908080359060200190929190505050607e565b005b60686088565 b6040518082815260200191505060405180910390f35b80600081 90555050565b6000805490509056fea265627a7a723158200e135 b4c7bcf7bde9dca1f257d97637d8137b315e29248b5654ac7830d ab9e8264736f6c63430005100032

If you look very closely, you get to find that, the "Contract Bytecode" contains the "Runtime Bytecode"

608060405234801561001057600080fd5b5060016000819055506 0c6806100276000396000f3fe6080604052348015600f57600 080fd5b506004361060325760003560e01c806360fe47b1146037 5780636d4ce63c146062575b600080fd5b6060600480360360208 11015604b57600080fd5b81019080803590602001909291905050 50607e565b005b60686088565b604051808281526020019150506 0405180910390f35b8060008190555050565b6000805490509056 fea265627a7a723158200e135b4c7bcf7bde9dca1f257d97637d8 137b315e29248b5654ac7830dab9e8264736f6c63430005100032

Metaphorically, the smart contract remain in a way of Fill in the Blanks! The arguments inside the function(), are the blanks, which gets filled, and the state of the Blockchain is changes, or the query result is returned.

Please Note! This thing is publicly available.

-> Will directly, continue in next microblog....

Day15 – “Why?” & “What in?” Security & Blockchain?

Reading Time: 2 minutes

author: aman

Blog IV - Part II - Day 15

Let us get some dirty hands on with some more Solidity code and exploit a few more Ethereum - Solidity bugs.

Here we'll discuss about the famous DAO attack, caused by the reentrancy bug.

Let us do it...

In this micro-blog

  • delegatecall (the proxy calls) (SWC-112) (Inclusion of Functionality from Untrusted Control Sphere)
  • DoS With Block Gas Limit (SWC - 128)
  • Integer Overflow (SWC - 101)
  • Reentrancy Bug(DAO attack) (Improper Enforcement of Behavioral Workflow) (SWC-107)
  • uncheckedSend() (SWC - 113)
  • tx.origin bug
  • Variable Shadowing (SWC-119)
3. Reentrancy Bug(DAO attack) (Improper Enforcement of Behavioral Workflow) (SWC-107)

You can find the related files in this gist.

There are two files. One is simpleDAO.sol which is a simple DAO(Decentralised Autonomous Organisation) contract, which is generally available publicily. Other one is reentrancy.sol which is particularly written by the attacker to exploit this bug.

It is termed as Improper Enforcement of Behavioral Workflow, as the attacker is able to make improper use of the conctract function, and play with the workflow of the contract.

Now, look at the 2 very crucial parts of both the contracts, one from each.

-> Attacking contract

function() public payable{

The variable DAO is the instantiation of the already deployed contract.

-> DAO Contract

function withdraw(uint amount) public{
    if (credit[msg.sender]>= amount) {

Now, just go with the flow.

You being the owner of the "attacking contract", will trigger some function to withdraw your money from the DAO Contract, the flow goes as follows:

call is sent to function withdraw() [DAO]


the function checks whether you have that amount, which comes to be true


amount is transferred to your contract using sender function


to accept the payment, "payable" function of your contract automatically gets called


The flow moves again to the "withdraw()" Notice!!! the amount is deducted after sending the amount your contract

"Notice the credit[msg.sender]-=amount; line."


The flow repeats.


This thing, drained off all the money from the DAO contract to the attacker contract.

"One of the major dangers of calling external contracts is that they can take over the control flow. In the reentrancy attack (a.k.a. recursive call attack), a malicious contract calls back into the calling contract before the first invocation of the function is finished. This may cause the different invocations of the function to interact in undesirable ways."

*Can you Imagine what the Solution was?

Well, I'll tell that in the next blog. laughing

You are surely gonna kill me for this.

Be honest!!! dont search it up

*will be dropping an "answer" box in the cev insta page @cevsvnit

Thank you.

Adding gist frames here

Reentrancy Bug(DAO attack) (Improper Enforcement of Behavioral Workflow) (SWC-107)

CEV - Handout