Blockchain block data structure

Multiple blockchains have block data strictures with different event granularities. A first blockchain adds blocks according to a data structure with high event granularity. A second blockchain adds a block digest according to a data structure with low event granularity. The block digest is a digest of the blocks added to the first blockchain.



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Blockchain Node Providers and How They Work


A ledger is a key concept in Hyperledger Fabric; it stores important factual information about business objects; both the current value of the attributes of the objects, and the history of transactions that resulted in these current values. A ledger contains the current state of a business as a journal of transactions. If you want to see how your balance was derived, then you can look through the transaction credits and debits that determined it.

This is a real life example of a ledger — a state your bank balance , and a set of ordered transactions credits and debits that determine it. Hyperledger Fabric is motivated by these same two concerns — to present the current value of a set of ledger states, and to capture the history of the transactions that determined these states. While the facts about the current state of a business object may change, the history of facts about it is immutable , it can be added to, but it cannot be retrospectively changed.

In Hyperledger Fabric, a ledger consists of two distinct, though related, parts — a world state and a blockchain. Each of these represents a set of facts about a set of business objects. The world state makes it easy for a program to directly access the current value of a state rather than having to calculate it by traversing the entire transaction log. The world state can change frequently, as states can be created, updated and deleted.

Transactions are collected inside blocks that are appended to the blockchain — enabling you to understand the history of changes that have resulted in the current world state. The blockchain data structure is very different to the world state because once written, it cannot be modified; it is immutable. We can also say that world state W is derived from blockchain B. In reality, the network maintains multiple copies of a ledger — which are kept consistent with every other copy through a process called consensus.

The term Distributed Ledger Technology DLT is often associated with this kind of ledger — one that is logically singular, but has many consistent copies distributed throughout a network.

The world state holds the current value of the attributes of a business object as a unique ledger state. A ledger world state containing two states. Both states are at version 0. A ledger state records a set of facts about a particular business object. An application program can invoke a smart contract which uses simple ledger APIs to get , put and delete states.

Notice how a state value can be simple Audi… or compound type:BMW…. The world state is often queried to retrieve objects with certain attributes, for example to find all red BMWs.

The world state is implemented as a database. This makes a lot of sense because a database provides a rich set of operators for the efficient storage and retrieval of states. Applications submit transactions which capture changes to the world state, and these transactions end up being committed to the ledger blockchain.

Applications are insulated from the details of this consensus mechanism by the Hyperledger Fabric SDK; they merely invoke a smart contract, and are notified when the transaction has been included in the blockchain whether valid or invalid. The key design point is that only transactions that are signed by the required set of endorsing organizations will result in an update to the world state.

If a transaction is not signed by sufficient endorsers, it will not result in a change of world state. You can read more about how applications use smart contracts , and how to develop applications. The version number is for internal use by Hyperledger Fabric, and is incremented every time the state changes.

The version is checked whenever the state is updated to make sure the current states matches the version at the time of endorsement. This ensures that the world state is changing as expected; that there has not been a concurrent update. Finally, when a ledger is first created, the world state is empty.

Because any transaction which represents a valid change to world state is recorded on the blockchain, it means that the world state can be re-generated from the blockchain at any time.

This can be very convenient — for example, the world state is automatically generated when a peer is created. Moreover, if a peer fails abnormally, the world state can be regenerated on peer restart, before transactions are accepted. Whereas the world state contains a set of facts relating to the current state of a set of business objects, the blockchain is an historical record of the facts about how these objects arrived at their current states.

The blockchain has recorded every previous version of each ledger state and how it has been changed. The blockchain is structured as sequential log of interlinked blocks, where each block contains a sequence of transactions, each transaction representing a query or update to the world state. In this way, all transactions on the ledger are sequenced and cryptographically linked together. This hashing and linking makes the ledger data very secure.

The blockchain is always implemented as a file, in contrast to the world state, which uses a database. This is a sensible design choice as the blockchain data structure is heavily biased towards a very small set of simple operations. Appending to the end of the blockchain is the primary operation, and query is currently a relatively infrequent operation. B0 is the first block in the blockchain, the genesis block.

In the above diagram, we can see that block B2 has a block data D2 which contains all its transactions: T5, T6, T7. Most importantly, B2 has a block header H2, which contains a cryptographic hash of all the transactions in D2 as well as a hash of H1. In this way, blocks are inextricably and immutably linked to each other, which the term blockchain so neatly captures! Finally, as you can see in the diagram, the first block in the blockchain is called the genesis block.

Instead, it contains a configuration transaction containing the initial state of the network channel not shown. We discuss the genesis block in more detail when we discuss the blockchain network and channels in the documentation. These fields are internally derived by cryptographically hashing the block data. They ensure that each and every block is inextricably linked to its neighbour, leading to an immutable ledger.

Block header details. The header H2 of block B2 consists of block number 2, the hash CH2 of the current block data D2, and the hash of the prior block header H1. This section contains a list of transactions arranged in order. It is written when the block is created by the ordering service. These transactions have a rich but straightforward structure, which we describe later in this topic. This section contains the certificate and signature of the block creator which is used to verify the block by network nodes.

Unlike the block data and header fields, this section is not an input to the block hash computation. Transaction details. Transaction T4 in blockdata D1 of block B1 consists of transaction header, H4, a transaction signature, S4, a transaction proposal P4, a transaction response, R4, and a list of endorsements, E4. This section, illustrated by H4, captures some essential metadata about the transaction — for example, the name of the relevant chaincode, and its version.

This section, illustrated by S4, contains a cryptographic signature, created by the client application. This field, illustrated by P4, encodes the input parameters supplied by an application to the smart contract which creates the proposed ledger update.

When the smart contract runs, this proposal provides a set of input parameters, which, in combination with the current world state, determines the new world state. This section, illustrated by R4, captures the before and after values of the world state, as a Read Write set RW-set. As shown in E4, this is a list of signed transaction responses from each required organization sufficient to satisfy the endorsement policy. That concludes the major fields of the transaction — there are others, but these are the essential ones that you need to understand to have a solid understanding of the ledger data structure.

The world state is physically implemented as a database, to provide simple and efficient storage and retrieval of ledger states. LevelDB is the default and is particularly appropriate when ledger states are simple key-value pairs.

A LevelDB database is co-located with the peer node — it is embedded within the same operating system process. CouchDB is a particularly appropriate choice when ledger states are structured as JSON documents because CouchDB supports the rich queries and update of richer data types often found in business transactions. Implementation-wise, CouchDB runs in a separate operating system process, but there is still a relation between a peer node and a CouchDB instance.

All of this is invisible to a smart contract. The world state database could be a relational data store, or a graph store, or a temporal database. This provides great flexibility in the types of ledger states that can be efficiently accessed, allowing Hyperledger Fabric to address many different types of problems.

The basic sample app creates a set of 6 assets each with a unique identity; a different color, size, owner, and appraised value. The ledger, L, comprises a world state, W and a blockchain, B. B contains two blocks, 0 and 1. Block 1 contains four transactions: T1, T2, T3, T4. ASSET1 has a value which indicates that it is a blue with size 5, currently owned by Tomoko, and we can see similar states and values for the other cars. Moreover, we can see that all car states are at version number 0, indicating that this is their starting version number — they have not been updated since they were created.

We can also see that the blockchain contains two blocks. Block 0 is the genesis block, though it does not contain any transactions that relate to cars.

We can see that block 1 is linked to block 0. We have not shown the other fields in the blocks or transactions, specifically headers and hashes. It gives you a fully worked example of an entire block with its transactions in glorious detail — but for now, you have achieved a solid conceptual understanding of a Hyperledger Fabric ledger.

Well done! In reality, each chaincode has its own world state that is separate from all other chaincodes. World states are in a namespace so that only smart contracts within the same chaincode can access a given namespace. A blockchain is not namespaced. It contains transactions from many different smart contract namespaces. You can read more about chaincode namespaces in this topic. In Hyperledger Fabric, each channel has a completely separate ledger. This means a completely separate blockchain, and completely separate world states, including namespaces.

It is possible for applications and smart contracts to communicate between channels so that ledger information can be accessed between them. You can read more about how ledgers work with channels in this topic. See the Transaction Flow , Read-Write set semantics and CouchDB as the StateDatabase topics for a deeper dive on transaction flow, concurrency control, and the world state database.



Data Structures in Distributed Ledgers: Blockchain and Directed Acyclic Graph

In this section, we will guide you through the initial process of tracking transactions in a blockchain explorer and describe the individual elements of Bitcoin blocks. Following this part, you will have an introductory experience with blockchain explorers and individual blocks. Hello, Sovryn community. In the Recent block section on the right, click the top-most block in the Block height column. Blockchain explorers like the one we are using are really handy when tracking transactions or proving a transaction was sent.

The data stored inside each block depends on the type of blockchain. For instance, in the Bitcoin blockchain structure, the block maintains data.

Mastering Bitcoin by

A blockchain is a data structure containing records, called blocks , which are linked together in a cryptographically secure way. It's a distributed, publicly agreed upon ledger of transactions, and the fundamental technology of cryptocurrencies like bitcoin. A blockchain is a special type of linked list. Each list item contains its own information and a pointer to the next item in the list. When looking for a linked list item, you traverse it one item at a time, using that item's information to find the next item, then repeating the process. This process is a useful way to structure data, partly because you can splice two lists together by changing a single pointer. Blockchains are a little different because they link backward rather than forward. When a new block is created, it points to the preceding block. Blockchain is effective as a distributed ledger technology, or DLT. A distributed ledger is openly shared with all participants — there are no private transactions.


Blockchain data structure and how Blockchain works

blockchain block data structure

One of the reasons blockchain has become so popular is that its design prevents anyone from deleting or changing a record once it has been created. Yet as businesses invest more and more in blockchain technology, it has piqued the interest of cybercriminals who have successfully attacked several blockchains — posing a significant threat that has researchers at the Monash Blockchain Technology Centre MBTC working hard on ways to increase the security of blockchain. Blockchain was designed to be secure. If any of the records are subsequently changed, the computed hash will no longer match the original hash — and the change will be detected.

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A blockchain index structure based on subchain query

Any data structure used to store information can be considered a database. Blockchain technology, at its core, is no more than a ledger to store information about transactions. To that point, blockchains can be considered databases. Blockchain databases bring the concept one step further and combine the best of both worlds. In this article, you will learn the benefits of blockchain databases and how they can be used in your IT infrastructure. To understand what blockchain databases are, it is crucial to understand what a blockchain is.


Blockchain Technology and Healthcare

The following article will help you learn the different components of blockchain technology effortlessly. Our software development company created this guide, where we describe the blockchain structure and its components and their interaction, namely:. The term blockchain was first described back in A group of researchers wanted to create a tool to timestamp digital documents so that they could not be backdated or changed. Further, the technique was adapted and reinvented by Satoshi Nakamoto. In , Nakamoto created the first cryptocurrency, the blockchain-based project called Bitcoin. In general, blockchain technology has the core characteristics of decentralization, accountability, and security.

At its most basic, a blockchain is a computer file used for storing data 'block' in the chain (see the next section on structure of a blockchain).

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A blockchain is a shared ledger where each new block of transactions is signed with a Nakamoto signature. The shared ledger can be seen as a series of blocks , each of which is presented for signing when it is created. Each block consists of a set of transactions , and each block is built on the previous blocks.


What is Blockchain

In the second of our hybrid learning series, our CLO considers what facilitators should do when designing and planning a hybrid course. Learners in the room must have an equal opportunity to learn from their peers dialling in and vice versa. So, how do we provide this equal, inclusive learning experience? The upshot is our facilitators need to design and plan differently to deliver successful hybrid learning experiences. Below is my checklist so that none of our participants feel inferior because of their location: - Which comes first… programme design or available technology?

Wide Area Protection System WAPS undertakes the important task of maintaining system reliability and stability when the power system is subject to abnormal or predetermined unstable conditions.

How a Block in the Bitcoin Blockchain Works

Blockchain is similar to Single Linked List but there are many differences between these two. In a Single Linked list , there are a set of nodes connected to each other through a pointer. Every node has a pointer that points to the next node in the list and it is not possible to trace back to the previous node from the current node. In Blockchain , similar to single linked list, each block is connected to each other. But in Blockchain the flow of trace is opposite to single linked list.

There's also live online events, interactive content, certification prep materials, and more. The blockchain data structure is an ordered, back-linked list of blocks of transactions. The blockchain can be stored as a flat file, or in a simple database.


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