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Blockchain Block Structure

Developer Guide - Bitcoin

Developer Guide - Bitcoin

BETA: This documentation has not been extensively reviewed by Bitcoin experts and so likely contains numerous errors. Please use the Issue and Edit links on the bottom left menu to help us improve. Click here to close this disclaimer. X The Developer Guide aims to provide the information you need to understandBitcoin and start building Bitcoin-based applications, but it is not aspecification . To make the best use ofthis documentation, you may want to install the current version of BitcoinCore, either from source or from a pre-compiled executable . Questions about Bitcoin development are best asked in one of the Bitcoin development communities .Errors or suggestions related todocumentation on Bitcoin.org can be submitted as an issue or posted to the bitcoin-documentation mailing list . In the following documentation, some strings have been shortened or wrapped: []indicates extra data was removed, and lines ending in a single backslash \are continued below. If you hover your mouse over a paragraph, cross-referencelinks will be shown in blue. If you hover over a cross-reference link, a briefdefinition of the term will be displayed in a tooltip. The block chain provides Bitcoins public ledger, an ordered and timestamped recordof transactions. This system is used to protect against double spending and modification of previous transaction records. Each full node in the Bitcoin network independently stores a block chain containing only blocks validated by that node . When several nodes allhave the same blocks in their block chain , they are considered to be in consensus . The validation rules these nodes follow to maintain consensus are called consensusrules . This section describes many ofthe consensus rules used by Bitcoin Core. The illustration above shows a simplified ve Continue reading >>

Blockchain: What Is In A Block?

Blockchain: What Is In A Block?

In my previous article, I tried to described the concept of a blockchain with code. This time, I'll try to describe the structure of a single block. I will use the Bitcoin blockchain to explain blocks, but keep in mind that the concepts will remain more or less the same. It could be useful to read my last article to understand a few things first. A block is a container data structure. In the Bitcoin world, a block contains more than 500 transactions on average. The average size of a block seems to be 1MB ( source ). In Bitcoin Cash ( a hard fork from the Bitcoin blockchain ), the size of a block can go up to 8MB. This enables more transactions to be processed per second. Anyway, a block is composed of a header and a long list of transactions. Let's start with the header. The header contains metadata about a block. There are three different sets of metadata: The previous block hash. Remember that in a blockchain, every block is inherits from the previous block because we use the previous block's hash to create the new block's hash. For every block N, we feed it the hash of the block N-1. Mining competition. For a block to be part of the blockchain, it needs to be given a valid hash. This contains the timestamp, the nonce and the difficulty. Mining is another crucial part of the blockchain technology, but it is outside the scope of this article. The third part is a merkle tree root. This is a data structure to summarize the transactions in the block. And we will leave it at that for now. More on this later. To identify a block, you have a cryptographic hash, a digital signature if you will. This is created by hashing the block header twice with the SHA256 algorithm. For example, this is a block . I will refer to this block as an example for this article. The block header Continue reading >>

A Gentle Introduction To Ethereum

A Gentle Introduction To Ethereum

Ethereum builds on blockchain and cryptocurrency concepts, so if you are not familiar with these, its worth reading a gentle introduction to bitcoin and a gentle introduction to blockchain technology first. This article assumes the reader has a basic familiarity with how Bitcoin works. Ethereum is software running on a network of computers that ensures that data and small computer programs called smart contracts are replicated and processed on all the computers on the network, without a central coordinator. The vision is to create an unstoppable censorship-resistant self-sustaining decentralised world computer. The officialwebsite is Itextends the blockchain concepts from Bitcoin which validates, stores, and replicates transaction data on many computers around the world (hence the term distributed ledger). Ethereum takes this one step further, and also runs computer code equivalently on many computers around the world. What Bitcoin does for distributed data storage, Ethereum does for distributed data storage plus computations. The small computer programsbeing run are called smart contracts, and the contractsare run by participants on their machines using asort ofoperating system called a Ethereum Virtual Machine. To run Ethereum, you can download (or write yourself if you have the patience) some software called an Ethereum client. Just like BitTorrent or Bitcoin, the Ethereum client will connect over the internet to other peoples computers running similar client softwareand start downloading the Ethereum blockchain from them to catch up. It will also independently validate that each block conforms to the Ethereum rules. What does the Ethereum client software do? You can use itto: Create new transactions and smart contracts Your computer becomes a node on the network, r Continue reading >>

The Structure Of Blockchain Technology And How It Works.

The Structure Of Blockchain Technology And How It Works.

The structure of Blockchain Technology and How it works. By now, we should know that Blockchain Technology is going to make great impacts in nearly all industries in the future, and for good reasons financial institutions are finding very clever means to start testing and investing in this technology. Therefore, is its importance for us to understand the structure of blockchain and how it works. The structure of blockchain data is a well-ordered, back-linked list of transaction blocks. The blockchain can be kept in a simple database, or as a flat file. The Bitcoin Core client keeps the blockchain metadata using LevelDB database of Google. Blocks are connected back, each referring to the preceding block in the chain. Normally, blockchain is visualized as a vertical stack that has blocks layered on top of each other. The first stack serves as the basis of the stack. The conception of blocks stacked on each other results in the use of the terms such as tip or top to refer to the most newly added block , and height to refer to the distance between the first block and other blocks. Every block within the blockchain is recognized by a harsh, created with the SHA256 cryptographic hash algorithm on the block header. Every block also references a preceding block, referred to as the parent block. In other words, every block has the hash of its parent in its own header. The series of hashes connecting each block to its parent makes a chain going back to the first block, referred to as the genesis block. Although a block has one parent, it can momentarily have many children. Each child refers to the same block as its parents and has the same parent harsh. Many children appear when there is a blockchain fork, a short-term situation that happens when different blocks are found nearl Continue reading >>

How Miners Solve A Block, Anatomy Of A Block, Block Header Structure, Pooled Mining - Bitcoin For The Befuddled - Academic Library - Free Online College E Textbooks

How Miners Solve A Block, Anatomy Of A Block, Block Header Structure, Pooled Mining - Bitcoin For The Befuddled - Academic Library - Free Online College E Textbooks

Bitcoin mining requires a great deal of computational power, but what do miners calculate? They repeatedly calculate the double SHA256 hash6 of slight variations of certain information, called the block header, in their new block. When a block of transactions is created, the block header contains a summary of information about the block, including the time it was created, a hash of the transactions within the block, and other data, which we'll delve into shortly. Importantly, in the block header is a field for an arbitrary number called a nonce, which the miner chooses. In fact, it is the only part of the block that is under the full control of the miner. So how does a miner choose a value for this nonce? A solved block (i.e., a block that will be accepted by others as part of the blockchain and the one the miner is paid for) occurs when the double SHA256 hash of the block header results in a number that is less than some predetermined threshold, known as the difficulty target. If the result is greater than the target, the block remains unsolved. When this happens, the miner must try a different nonce, which is contained in the header and hence affects the hash. Because cryptographic hash functions produce completely new outputs when the input is changed by even the tiniest amount, changing the nonce value results in a totally new hash for the entire block header. By repeatedly changing the nonce value, eventually a hash output will be found that is less than the target. Typically, a miner simply increments the nonce by 1 in this search until a successful nonce value is found. When a working nonce is found, the block is solved. Let's take a closer look at a block's structure so you can see how the miners' actions fit into the big picture. At the top level, a Bitcoin bl Continue reading >>

Blockchain Data Structure

Blockchain Data Structure

This is a write up on Blockchain data structures. We delve into the different components of a block, and then how blocks are set up to interact with each other. The blockchain data structure is a back-linked list of blocks of transactions, which is ordered. It can be stored as a flat file or in a simple database. Each block is identifiable by a hash, generated using the SHA256 cryptographic hash algorithm on the header of the block. Each block references a previous block, also known as the parent block, in the previous block hash field, in the block header. A hash, also known in long form as cryptographic hash function, is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size.In the case of SHA 256, the result is a string of 32 bytes. The resultant 32 bytes makes it effectively impossible to reverse the output, since the function was designed to be a one-way function(Schneier, 2004). The idea behind a hash functions use is to facilitate a thorough means for searching for data in a dataset. The most basic form of hash function is any function that can be used to map data of arbitrary size to data of fixed size. This output is a bit-string known as the hash value, hash sum or hash code. The hash values can be stored in a tabular form known as a hash table and is an efficient indexing mechanism; especially useful in search performance (Peters & Panayi, 2015). Hash functions are collision-free too. That means its impossible to find two messages that hash to the same hash value (Narayanan, 2016). Therefore, when given a compact hash, one can confirm that it matches a particular input datum. Blocks can be identified from their hash, serving two purposes; identification and integrity verification. Bitcoin hashing function makes use of the S Continue reading >>

Block Structure. All About Cryptocurrency - Bitcoin Wiki

Block Structure. All About Cryptocurrency - Bitcoin Wiki

Each block, besides other components, contains in its header the record about several or all the recent transactions and record about the block that came just before the current. To create a new block miner has to solve the task that network provides. Each block has its unique solution, which is also written in the blockheader. This task is difficult to solve and it takes a lot of time, but as soon as one of the users (miners) solves the task, the network very quickly confirms the solution is correct. There are several solutions for each block and its enough to find at least one of them. Since the reward for finding the block is 25 BTC, block also includes Bitcoin address , so reward is sent to it. The record of the transaction is called generation transaction, i.e. transaction of Bitcoin generation; it is always on the 1st place in the block transactions list. Bitcoin transactions are broadcasted by sender to the entire network; nodes collect information about them and guided by certain conditions include them in the found block. The complexity of the task is regulated by Bitcoin so 6 blocks could be found per hour on average (1 block within 10 minutes). Every 2016 blocks (approximately every 2 weeks) the complexity in the network is changing - every Bitcoin client compares how much faster (slower) blocks have been found in comparison with standard values and, based on these data, the complexity is regulated to higher (lower) side. Since each block has a reference in its heading to the previous one, we can say that they form a chain . There is a possibility that the chain can be divided, for example, if 2 miners simultaneously find a solution for a new block. Bitcoin system is configured to solve such chain branching as soon as possible, leaving only one branch. Rewar Continue reading >>

Bitcoins Implementation Of Blockchain

Bitcoins Implementation Of Blockchain

Bitcoin is the first to implement the concept of Blockchain We have already covered the basics of Blockchain in our previous post . Blockchain is a digital distributed ledger where data in each block is immutable and the blocks are ordered by timestamp. Today, the concept of Blockchain is being applied to not just hundreds of crypto-currencies but also to many use-cases in the Banking and Finance industry and each has its own implementation. In fact Blockchain has been extended to every industry -supply chain management, real estate, retail to name a few. In my opinion, one should always start with Bitcoin, to learn a practical implementation of Blockchain. Bitcoin is the first and time-tested implementation used by millions. Rest all blockchain implementations are still in proof of concept phase. Block Structure Bitcoin. Number in brackets is the size in bytes. Each individual cell is 1 byte. Hence a field of 4 bytes occupies 4 cells. Fields from Version till Nonce form the block header (Total 80bytes) To learn more on Bitcoin read one of my initial post . Every block in the Bitcoin network has the exact same structure as per the above diagram. Each newly created block is chained to the last added block of the blockchain and stores its digital finger print. Let us examine the fields of a Block - Magic number (4 bytes): This is an identifier for the Blockchain network. It has a constant value of 0xD9B4BEF9. It indicates a) Start of the block b) Data is from production network. You can read more on this concept on wiki . Block size(4 bytes): Indicates how large the block is. Since the very beginning till as of today (Dec 2016) each block is fixed to 1 MB. However a proposal might soon have the consensus of the core development team (who can change protocol rules) and th Continue reading >>

Block - Bitcoin Wiki

Block - Bitcoin Wiki

Transaction data is permanently recorded in files called blocks. They can be thought of as the individual pages of a city recorder's recordbook (where changes to title to real estate are recorded) or a stock transaction ledger. Blocks are organized into a linear sequence over time (also known as the block chain ). New transactions are constantly being processes by miners into new blocks which are added to the end of the chain and can never be changed or removed once accepted by the network (although some software will remove orphaned blocks). number of bytes following up to end of block Each block contains, among other things, a record of some or all recent transactions , and a reference to the block that came immediately before it. It also contains an answer to a difficult-to-solve mathematical puzzle - the answer to which is unique to each block. New blocks cannot be submitted to the network without the correct answer - the process of " mining " is essentially the process of competing to be the next to find the answer that "solves" the current block. The mathematical problem in each block is extremely difficult to solve, but once a valid solution is found, it is very easy for the rest of the network to confirm that the solution is correct. There are multiple valid solutions for any given block - only one of the solutions needs to be found for the block to be solved. Because there is a reward of brand new bitcoins for solving each block, every block also contains a record of which Bitcoin addresses or scripts are entitled to receive the reward. This record is known as a generation transaction, or a coinbase transaction, and is always the first transaction appearing in every block. The number of Bitcoins generated per block starts at 50 and is halved every 210,000 bloc Continue reading >>

Explaining Directed Acylic Graph (dag), The Real Blockchain 3.0

Explaining Directed Acylic Graph (dag), The Real Blockchain 3.0

Explaining Directed Acylic Graph (DAG), The Real Blockchain 3.0 Partner Zeroth.AI. Founder RavenProtocol.com Rocco.AI GoodAudience.com Opinions expressed by Forbes Contributors are their own. Coins of the cryptocurrencies Ethereum and Bitcoin standon a table. (Photo by Thomas Trutschel/Photothek via Getty Images) The concept of blockchain as a standalone technology started gaining popularity in 2015. Prior to that, it was just known as a data structure underlying Bitcoin technology. In Satoshi Nakamotos white paper, the two words block and chain appeared together. It was only called a chain of blocks. Bitcoins rise into popularity resulted in it being categorized as Blockchain 1.0. With Ethereum making waves as a decentralized platform for applications that run exactly as programmed, more and more people began to categorize Ethereum as Blockchain 2.0. Now the market is battling to see who will be named Blockchain 3.0. Direct Acyclic Graph or DAG may be it. DAG is a directed graph data structure that uses a topological ordering. The sequence can only go from earlier to later. DAG is often applied to problems related to data processing, scheduling, finding the best route in navigation, and data compression. Bitcoin has always been inefficient due to the proof-of-work (POW) system. Blocks cant be created simultaneously. The linked storage structure allows for only one chain on the whole network. All the transactions occurring around the same time are kept in the same block. Miners then compete for the block validation. One single block is created about every 10 minutes. The first community to come up with the idea of changing the chain-like storage structure into a DAG of blocks was NXT . If the time of mining remains unchanged, the storage could be extended by X times wi Continue reading >>

Blockchain - Wikipedia

Blockchain - Wikipedia

For other uses, see Block chain (disambiguation) . Blockchain formation. The main chain (black) consists of the longest series of blocks from the genesis block (green) to the current block. Orphan blocks (purple) exist outside of the main chain. A blockchain [1] [2] [3] originally block chain [4] [5] is a continuously growing list of records , called blocks, which are linked and secured using cryptography . [1] [6] Each block typically contains a hash pointer as a link to a previous block, [6] a timestamp and transaction data. [7] By design, blockchains are inherently resistant to modification of the data. Harvard Business Review defines it as "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way." [8] For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires collusion of the network majority. Blockchains are secure by design and are an example of a distributed computing system with high Byzantine fault tolerance . Decentralized consensus has therefore been achieved with a blockchain. [9] This makes blockchains potentially suitable for the recording of events, medical records, [10] [11] and other records management activities, such as identity management , [12] [13] [14] transaction processing , documenting provenance , or food traceability . [15] The first blockchain was conceptualised in 2008 by an anonymous person or group known as Satoshi Nakamoto and implemented in 2009 as a core component of bitcoin where it serves as the public ledger for all transactions. Continue reading >>

Blockchain Architecture

Blockchain Architecture

Related to Software Engineering Best Practices ## PrefaceA blockchain is a mesh network of computers linked not to a central server but rather to each other. Computers in this network define and agree upon a shared state of data and adhere to certain constraints imposed upon this data.This shared state is simply a distributed state machine, with each "block" making a change to thecurrent, known, shared state.### A word about BitcoinThe Bitcoin project implemented the first large-scale blockchain.Bitcoins blockchain is "simple" in comparison to most of the other blockchains that exist today. For a beginner's look at Bitcoin, see this [guide](For the purposes of this article, we will mainly look to Bitcoin's blockchain when discussing aspects of blockchain architecture in general. However, thearchitectural components of **transactions**, **blocks**, **mining**, and **consensus** can begeneralized and implemented in many different ways, leading to various possible blockchain projects. These projects usually involve creating other cryptocurrencies (or [_alt-coins_][coin-market-cap]), but the diversity in blockchain-related project ideas is growing quickly.## Transactions[Transactions][transactions] are the things that give a blockchain purpose. They are the smallestbuilding blocks of a blockchain system.Transactions generally consist of a recipient address, a sender address, and a value. This is not toodifferent from a standard transaction that you would find on a credit card statement.A Bitcoin transaction moves the value of some bitcoin from one address to another address.A transaction _changes the state_ of the agreed-correct blockchain. A blockchain is a shared, decentralized, distributed state machine. This means that all [nodes][nodes] (users of the blockchain system Continue reading >>

Blockchain Explained - Part 2

Blockchain Explained - Part 2

The blockchain has tremendous potential for fraud prevention and cyber security. With this series of articles, we will explore how the blockchain will change the cyber risk game. In my first article , I have introduced the blockchain concept, presents what it is in the light of its initial deployment in the Bitcoin project, key problems solved by blockchain, and the blockchain operation principle. With this second part, we dig into the technical aspects to complete our thorough introduction to blockchain. Concrete business applications and evolutions will be discussed in an article to follow in the coming weeks. In the Bitcoin system, a blockchain is a transaction database shared by all nodes participating in a system based on the Bitcoin protocol. A full copy of a currency's block chain contains every transaction ever executed in the currency. With this information, one can find out how much value belonged to each address at any point in history. The blockchain data structure is an ordered, back-linked list of blocks of transactions. Every block contains a hash of the previous block. This has the effect of creating a chain of blocks from the genesis block to the current block. Each block is guaranteed to come after the previous block chronologically because the previous block's hash would otherwise not be known. Each block is also computationally impractical to modify once it has been in the chain for a while because every block after it would also have to be regenerated. Transaction data is permanently recorded in these blocks as if they were files. These blocks can be thought of as the individual pages of a city recorder's recordbook (where changes to title to real estate are recorded) or a stock transaction ledger. Over time, blocks are organized into a linear sequ Continue reading >>

Structure Of A Transaction

Structure Of A Transaction

A transaction records bitcoins transfers between participants. We call "asset" an amount in bitcoins that has been assigned to a user. An asset materializes: a payment, similar to a cheque, when a transaction has just been created, and is transferred as a message, a ledger entry, when a transaction has been recorded in a block of the blockchain. The Bitcoin transaction consists of two tables, the input table, which lists the assets spent by one or more payers and the outputs table, which lists new assets assigned to one or more payees. When a payee wants to use an asset as a payer, a new transaction is created, and that asset will appear in the new input table. Each input table entry references an asset of an output table entry of a previous transaction. This reference consists of the identifier of the transaction that assigned it, and an entry number in the output table. The total amount of assets allocated may be less than the sum of the assets spent. If there is a difference, this difference will be automatically assigned to the miner who recorded the transaction in a block. This difference will be considered as a transaction fee. The diagram below shows the structure of a transaction and the locks set with the user's private keys. A Bitcoin address will act as an account number associated with an asset: the public key is obfuscated with a double hashing and encoded in an alphanumeric to facilitate the communication by the payee to the payer. To receive a payment, the payee generates a private key, a public key is calculated and transformed into a Bitcoin address, which will be communicated to the payer, to add output entries of the new transaction. To make a payment, the payer creates a new transaction, to assign bitcoins to the payee Bitcoin address, and to collec Continue reading >>

Block Structure Tendermint Documentation

Block Structure Tendermint Documentation

a Header contains merkle hashes for various chainstates the Data is all transactions which are to be processed the LastCommit > 2/3 signatures for the last block The signatures returned along with block H are those validatingblock H-1. This can be a little confusing, but we must also considerthat the Header also contains the LastCommitHash. It would beimpossible for a Header to include the commits that sign it, as it wouldcause an infinite loop here. But when we get block H, we findHeader.LastCommitHash, which must match the hash of LastCommit. The Header contains lots of information (follow link for up-to-date info). Notably,it maintains the Height, the LastBlockID (to make it a chain),and hashes of the data, the app state, and the validator set. This isimportant as the only item that is signed by the validators is theHeader, and all other data must be validated against one of themerkle hashes in the Header. The DataHash can provide a nice check on the Data returned in this same block. If you are subscribed to new blocks, viatendermint RPC, in order to display or process the new transactions youshould at least validate that the DataHash is valid. If it isimportant to verify autheniticity, you must wait for the LastCommitfrom the next block to make sure the block header (includingDataHash) was properly signed. The ValidatorHash contains a hash of the current Validators .Tracking all changes in the validator set is complex, but a client canquickly compare this hash with the hash of the currently knownvalidators to see if there have been changes. The AppHash serves as the basis for validating any merkle proofsthat come from the ABCIapplication . It represents thestate of the actual application, rather that the state of the blockchainitself. This means its necessary in or Continue reading >>

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