Friday, October 7, 2022

How To Implement Blockchain In Java

Export Credentials To Communicate With The Blockchain Network

Implementation of BlockChain with Java

For Open Liberty to communicate to the blockchain network, Hyperledger Fabric has security features that stop applications attempting to make transactions unless you have the specific profiles and certificate authorities.

  • Export the Local Fabric Gateways:

  • In the FABRIC GATEWAYS panel, select 1 Org Local Fabric Org1.

  • Choose an identity to connect with will appear from the command palette. Select admin.

  • Hover over the FABRIC GATEWAYS heading, and click > Export connection profile.

  • The finder window will open.

  • Navigate to Users/Shared/.

  • Create a new folder FabConnection.

    The full path directory should be Users/Shared/FabConnection.

  • Save the .json file as 1-Org-Local-Fabric-Org1_connection.json.

  • Export the Fabric Wallets:

  • In the FABRIC WALLETS panel, select 1 Org Local Fabric, then right-click Org1, and select Export Wallet.

  • Save the folder as wallet in the /Users/Shared/FabConnection/ directory.

  • Testing The Wallets And Signatures:

    Now we are almost halfway done Lets test a few things are working. In the NoobChain class lets add some new variables and replace the content of our mainmethod :

    We created two wallets, walletA and walletB then printed walletAs private and public keys. Generated a Transaction and signed it using walletAs private key. Finally we crossed our fingers and hoped everything worked out.

    Your output should look something like this :

    Time to pat your self on the back. Now we just need to create/verify the outputs and inputs and then store the transaction in the Blockchain.

    How To Implement Blockchain

    Before businesses implement blockchain technology, it is imperative that they first identify what is its best and most relevant use to cement blockchain as a profitable asset rather than a costly liability.

    However, as a business leader, you need to first admit that blockchain is here to stay. You simply cant ignore it anymore. On top of this fact, it provides practical solutions to many of your daily business functional issues.

    The best possible move is to implement blockchain. Lets get started with it!

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    A Gentle Introduction To Blockchain

    This is IBMs Free eBook.

    This is one of the best blockchain books because, well, its free! This is not the free online resource IBM gives out.

    IBM also has a tutorial on how to implement blockchain from scratch using Python. View it here.

    Blockchain In A Nutshell

    What Is Blockchain In Java

    Lets first give a quick summary of blockchain. A block contains some header information and a set or block of transactions of any type of data. The chain starts with a first block. As transactions are added/appended, new blocks are created based on how many transactions can be stored within a block.

    When a block threshold size is exceeded, then a new block of transactions is created. The new block is linked to the previous block, hence the term blockchain.


    Blockchains are immutable because an SHA-256 hash is computed for transactions. A blocks contents are also hashed which provide a unique identifier. Moreover, the hash from the linked, previous block is also stored and hashed in the block header.

    This is why trying to tamper with a blockchain block is basically impossible, at least with current computing power. Heres a partial Java class definition showing the properties of the block.

    ...public class Block< T extends Tx>  {public long timeStamp private int index private List< T>  transactions = new ArrayList< T> private String hash private String previousHash private String merkleRoot private String nonce = "0000" // caches Transaction SHA256 hashes    public Map< String,T>  map = new HashMap< String,T> ...

    Notice the injected generic type is of type Tx. This allows transaction data to vary. Also, the previousHash property will reference the previous blocks hash. The merkleRoot and nonce properties will be described in a bit.

    Block Hash

    The Chain

    Merkle Trees

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    Step : Generating Hashes:

    In this step, we will implement the SHA256Helper. It is pretty convenient to implement this procedure in Java because we rely on the built methods and built-in classes of Java security.

    Firstly we will import the MessageDigest, and further will generate the hash for our Blockchain.

    Question: How many SHA256 hashes are there?

    Answer: One hash takes up 256 bits in memory with binary values 0 and 1. Therefore, we can conclude that the total number of hashes is 2256. If you are dealing with hexadecimal values, there are 64 hexadecimal characters therefore, it yields 1664 hash values.

    Refer to the given below program to generate the Blockchain hashes in Java:

    Sharding Data Structure In My Simulation

    As there is a variety of different ways of implementing sharding in Blockchain, I will apply a relatively simple approach here. Lets treat the Block data structure from previous code as Sub-Block, and redefine the Block as a collection of Sub-Blocks. The entire Blockchain data structure should look like the figure below:

    Now every mining iteration, based on the transactions load, the Blockchain system would decide to divide next Block into a proper number of shards, and evenly distribute compute powers to each of the shards. Miners of different shards will concurrently compute the satisfying nounce for the shard they belong to. For N shards, there will be N winners. Each of them will be able to generate a new sub-block and all the sub-blocks will be gathered together as a whole new Block to be attached to the Blockchain.

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    Implement Mining Into The Blockchain

    So let’s implement this in our simple Blockchain!

    Let’s start by adding a nonce to our Block class:


    The nonce is the only value inside our block that we can change to influence the hash of the block. We can’t change the timestamp or the data!

    Next, let’s create a mineBlock method that will actually perform the magic of mining a block. This method will receive the required difficulty as a parameter and will keep running until the hash of our block starts with enough zeros:

    mineBlock console.log }

    I just created a simple while loop that keeps running until our hash starts with enough zeros. We use the difficulty to know how many zeros are required. A difficulty of 5 means that our hash has to start with 5 zeros.

    Every time our hash doesn’t have enough zeros, we increase the nonce by 1 and calculate the hash again. And if we found a hash that matches the difficulty, we log it to the console. Easy!

    There’s one more thing we need to do. In our calculateHash function, we’re actually not taking the nonce variable into account, so I’ll add it:


    Problem solved!

    Inputs & Outputs : How Crypto Currency Is Owned

    Blockchain Implementation in Java

    For you to own 1 bitcoin, you have to receive 1 Bitcoin. The ledger doesnt really add one bitcoin to you and minus one bitcoin from the sender, the sender referenced that he/she previously received one bitcoin, then a transaction output was created showing that 1 Bitcoin was sent to your address. .

    Your wallets balance is the sum of all the unspent transaction outputs addressed to you.

    From this point on we will follow bitcoins convention and call unspent transaction outputs: UTXOs.

    So lets create a TransactionInputClass:

    And a TransactionOutputs Class:

    Transaction outputs will show the final amount sent to each party from the transaction. These, when referenced as inputs in new transactions, act as proof that you have coins to send.

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    Idle Chains Are A Security Liability

    Blockchains like Bitcoin and Ethereum see a constant stream of new transactions to fill up their blocks, with an adaptive mining difficulty to keep the time between blocks roughly constant . In our use case, however, it is expected that there are periods of decreased or even no activity. On the one hand, all users are in the same time zone, meaning that periods of nightly inactivity can be expected. On the other hand, during winter or when energy generation is likely to be insignificant, there are no portions transferred as there would be no financial gain for either party. Thus, it is possible that there may be no unconfirmed transactions for several hours or even days within the network.

    This could be used by an attacker to pre-mine a longer chain than the rest of the network during the idle time and subsequently deliberately exclude certain transactions from the longest chain. This issue has been addressed in related work on proof-of-work security from the pre-blockchain-era as well as in for a protocol similar to Bitcoin and in for Bitcoin itself. Although Bitcoin and Ethereum assume that there is always a significantly high number of transactions to keep the network active, they both allow for mining empty blocks .

    Now We Need A Way To Check The Integrity Of Our Blockchain

    Lets create an isChainValidBoolean method in the NoobChainclass, that will loop through all blocks in the chain and compare the hashes. This method will need to check the hash variable is actually equal to the calculated hash, and the previous blocks hash is equal to the previousHash variable.

    Any change to the blockchains blocks will cause this method to return false.

    On the bitcoin network nodes share their blockchains and the longest valid chain is accepted by the network. Whats to stop someone tampering with data in an old block then creating a whole new longer blockchain and presenting that to the network ? Proof of work. The hashcash proof of work system means it takes considerable time and computational power to create new blocks. Hence the attacker would need more computational power than the rest of the peers combined.

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    Inputs & Outputs : Processing The Transaction

    Blocks in the chain may receive many transactions and the blockchain might be very, very long, it could take eons to process a new transaction because we have to find and check its inputs. To get around this we will keep an extra collection of all unspent transactions that can be used as inputs. In our NoobChainclass add this collection of all UTXOs:

    Okay, time to get down to the nitty gritty

    Lets put everything together to process the transaction with a processTransaction booleanmethod in our TransactionClass:

    With this method we perform some checks to ensure that the transaction is valid, then gather inputs and generating outputs. .

    Importantly, towards the end, we discard Inputs from our list of UTXOs, meaning a transaction output can only be used once as an input Hence the full value of the inputs must be used, so the sender sends change back to themselves.

    Finally lets update our wallet to:

    • Gather our balance )
    • And generate transactions for us

    Pros Of Using Java Programming Language

    Techie Jackie Blogs: Blockchain Implementation With Java Code

    Sun Microsystems created this strongly typed object and class-based programming language. This language is popular and used all around the world in developing big projects.

    Let us learn about the advantages that it offers:

    • The difficulty level is much lower than C or C++
    • Independent from the operational system
    • The easy Memory allocation process
    • Large libraries collection
    • Effortless Memory cleaning

    Few Drawbacks which you must be aware of when choosing the programming language are as follows:

    • Slower as compared to C++ or Golang
    • Always need JVM to run

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    Why Do We Need Blockchain

    Here, are some reasons why Blockchain technology has become so popular.

    Resilience: Blockchains is often replicated architecture. The chain is still operated by most nodes in the event of a massive attack against the system.

    Time reduction: In the financial industry, blockchain can play a vital role by allowing the quicker settlement of trades as it does not need a lengthy process of verification, settlement, and clearance because a single version of agreed-upon data of the share ledger is available between all stack holders.

    Reliability: Blockchain certifies and verifies the identities of the interested parties. This removes double records, reducing rates and accelerates transactions.

    Unchangeable transactions: By registering transactions in chronological order, Blockchain certifies the unalterability, of all operations which means when any new block has been added to the chain of ledgers, it cannot be removed or modified.

    Fraud prevention: The concepts of shared information and consensus prevent possible losses due to fraud or embezzlement. In logistics-based industries, blockchain as a monitoring mechanism act to reduce costs.

    Security: Attacking a traditional database is the bringing down of a specific target. With the help of Distributed Ledger Technology, each party holds a copy of the original chain, so the system remains operative, even the large number of other nodes fall.

    One Communication Thread Is Not Enough

    When we initially designed the peer-to-peer communication for our node implementation, we dedicated one thread to handle all the messages to be sent to the nodes peers. This means that one thread with a message queue would process the messages to be sent one by one and other threads, e.g., the miner, would place the messages to be sent in this queue. In a small and stable network, this works fine. However, when connections are lost or the number of nodes is larger, communication can slow down significantly or even come to a halt.

    When a connection is lost, the timeout can take several seconds to be noticed by the transport layer. In the meantime, the communication thread waits for a reply or a timeout and is not able to process other messages from its queue. This leads to the remaining nodes not receiving further messages until the timeout is noticed. Communication is slowed down significantly if timeouts occur often, e.g., when a node has an unstable network connection or is offline.

    Similarly, when the number of nodes increases in a stable network, the message queue fills up because each message transmission is synchronous and the time required to send messages exceeds the time it takes to mine a new block.

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    Java Programming Language For Blockchain

    The moment we hear the term Java, the features that come to our mind are reliable, sturdy, and safe, and these are absolutely true. Java is highly popular and versatile that helps design performant Ethereum clients and tools to use in production environments. Given the size and maturity of its development community to more technical reasons such as speed, extensibility, and maintenance, it is the best language especially for large applications such as an Ethereum client.

    Though it is a known fact that high-level languages like Python have become more popular and that back-end developers mostly use JavaScript, the use of the Java programming language in the developer community has still not eroded like languages such as C++ and C#. Monitoring tools like JMX or Java Mission Control help easily manage applications.

    Java is an object-oriented programming language used in blockchain. It helps in writing highly portable codes. It is best known for its functionality i.e. write once run anywhere, which means you can run the code on all devices having a java virtual machine . Therefore, this application is used to create a simple and immutable platform for the blockchain.

    Let us now look at some of the features of the Java language that make it suitable for blockchain.

    Features of Java

    Here are some of the significant features of the Java programming language which make it a reasonable choice for developing Blockchain.

    Other important features of Java are as follows-

    Transaction Pool And Mining

    Blockchain Programming in Java

    The messages would be stored in a relational database via an INSERT. Transaction properties and transaction level ensure that parallel write and read accesses meet certain requirements and define how secure they should be. In this way, a transaction is opened before the INSERT and, if no errors occur, written into the database using a COMMIT.

    Since the data is not stored centrally in the blockchain, but a copy of all data is stored on any number of network nodes and any number of users want to store data in parallel, we need a different mechanism to obtain transaction security. This is where the transaction pool and mining come in. There are basically two areas in the blockchain in which data resides. On the one hand, this is the transaction pool in which the data still to be written is located, and on the other hand the blockchain itself with the data no longer to be changed . To prevent the network nodes from writing transactions into the blockchain at the same time, we need to overcome a mathematical challenge. You take any freely selectable transactions from the transaction pool and generate a hash from them. This hash must now begin with one, two, or three zeros, depending on the level of difficulty.

    long tries = 0 while )   tries++ }

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    Blockchain May Seem Like A Complicated Subject But Were Shedding Some Light On It

    Weve all seen how big Bitcoin and other cryptocurrencies have become. While this type of online currency is notoriously volatile, the technology behind it has the potential to disrupt every industry from the inside out. Because blockchain has an endless application scope, its being seen in new ways every day.

    In this post, well go into the architecture behind blockchain and how a distributed ledger works. Once you see it for yourself, youll see why so many developers are embracing blockchain as a new normal. Well also dive into a short tutorial for how to create your own blockchain sequence and use a proof of work system.

    Use Of Blockchain Technology

    The reasons for building this use case atop a blockchain are manifold. First, a global state needs to be stored that all parties agree on. Second, customers do not fully trust each other and malicious customers may attempt to double-spend their portions in order to profit. Third, there is no single trusted third party due to the number of stakeholders involved. Therefore, a private and permissioned blockchain is implemented. In , the use case requirements for such a blockchain are defined as follows:

    In our private and permissioned blockchain, a consortium of energy providers and network operators assigns permissions to new customers. These permissions allow customers to interact, i.e., read from and write to, the blockchain, similar to . A revocation process ensures that inactive users no longer participate in the blockchain.

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