Blockchain general terms

51% Attack
An attack on the distributed ledger that results in miners group has controlled more than 50% of the mining hashrate of the network. The term “Attack,” is used mostly in context to Bitcoin.


Addresses are used to receive and send transactions on the network. An address is a string of alphanumeric characters, but can also be represented as a scannable QR code. The address is generated using the private key.

Airdrop means distributing the free tokens to stakeholders as rewards. Airdrop is related to the blockchain projects, especially ICOs. Also, it might or might not include an incentive. Many blockchain projects perform airdrop for various reasons like community growth, fixing the bugs or incentivize a positive effort towards their idea.

Accidental Fork
An Accidental Fork happens when two or more miners select the block simultaneously. Then, one chain becomes longer than other. Also, the network abandons blocks that are not included in the long chain. These blocks are referred to as “orphan blocks.”
→ See also: Fork

Agreement Ledger
An agreement ledger is considered as a distributed ledger (DL), where two or more parties use it to negotiate and reach an agreement.

Application Programming Interface (API) refers to a software intermediary that enables two different applications to interact with each other. These interfaces define ways to do communication between several components.

ASIC is a type of computer processing chip that performs a singular function.
Due to its specialization, an ASIC is much more efficient and cost-effective than a generalized computer processor that can perform many functions. In the blockchain industry, ASIC boards have been used to perform the SHA-256 hashing required for Proof-of-Work (PoW), greatly outstripping the hashrate of even the most powerful GPU miners.

Asymmetric Cryptography (Public Key Cryptography)
Asymmetric cryptography, is also known as public key cryptography. It uses public keys and private keys to encrypt and decrypt data. The keys are large numbers that have been paired together but are not identical (asymmetric). A public key can be shared with everyone. The private key in the pair is kept secret. Protocols such as SSH, S/MIME rely on asymmetric cryptography for encryption and digital signature functions.

Attestation Ledger
An attestation ledger is an account book, created to provide evidence of individual transactions. The ledger is to used to check that agreement, statement or commitment of transaction was made.


Capital ‘B’ in Bitcoin refers to the Bitcoin network.

Lowercase ‘b’ in bitcoin refers to the token/cryptocurrency bitcoin.

Blocks are packages of data that carry permanently recorded data on the blockchain network.
→ See also: Orphan Blocks, Stale Blocks, Uncle Blocks

Block Height
Block height represents the number of blocks linked together in the blockchain. For example, the height 0 is the first block that is also known as Genesis Block.

Block Reward
When miner solves the block successfully, they receive the reward as a block reward. Miner needs to add the first transaction on the block to claim the reward. The reward can also be shared with a group of miners based on the amount of work they have done.

A blockchain is a distributed ledger that comprises of immutable records. Each block is then linked to the next block with a cryptographic signature. It enables block chains to be used like a ledger that can be shared and accessed by anyone having the right permissions. The blockchain is the transparent ledger that is used to save identities, value, agreements, credentials and property rights. Once you add something to the ledger, it will stay there forever.
→ See also: Consortium Blockchain, Private Blockchain, Public Blockchain

Blockchain Explorer
Blockchain explorer is a type of tool, which is used to check the past or current transactions on a blockchain. Also, it provides you with more details like transaction growth and network hashrate. By understanding blockchain explorer, you can enhance your knowledge about blockchain definitions.

Burning refers to the Proof-of-Burn consensus algorithm. Burning coins is the action of sending them to an address where they are irretrievable. As a miner, the more coins you burn, the better chance you have of being selected to mine the next block, thus earning more rewards.


Central Ledger
The central or general ledger works like a central repository that keeps records of transactions of assets and liabilities, revenues, expenses, owner’s equity etc.

Chain linking
Chain linking is the process to connect two blockchains so that transactions between the chain could take place. Blockchain like bitcoin can communicate with other side chains by enabling the assets exchange between them.

Confirmation means the transactions occurred on the blockchain has been verified by the network. It happens through a process called mining in a Proof-of-Work (PoW) system. When a transaction is confirmed, it cannot be double spent or reversed. The more confirmations an transaction has, the harder it becomes to make a double-spending attack.

Consensus Algorithm
Consensus algorithm is the blockchain element that determines how consensus is reached on that blockchain. In other words, it is the part of the blockchain protocol that describes who gets to validate blocks of data (and thus is entitled to the reward) and how others can verify its legitimacy. All participating entities on the blockchain must adhere and follow the same consensus algorithm to participate on the blockchain.
→ See also: PoS, PoW, Pos/Pow Hybrid, PBFT

A digital currency that is based on mathematics, where encryption techniques regulate the units of currency and verify the fund’s transfer. Also, cryptocurrencies are the representations of digital assets. Some of the popular cryptocurrencies are EOS, Bitcoin, NEO, Litecoin and Ethereum. Network stakeholders can buy or mine the cryptocurrency. Also, there are more ways to get hold of them including airdrop, staking or bounties.

Consortium Blockchain
is a blockchain, where a pre-selected set of nodes handles consensus process. It is also called permissioned blockchain network that can be a hybrid model built between trusted entity model of private blockchains and low trust provided by the public blockchain. In this, the access to read the transactions can be public or restricted to the participants. Moreover, these types of blockchains may be referred to as “partially decentralized.”
→ See also: Blockchain, Private Blockchain, Public Blockchain

Cryptography is the encryption and decryption of data. There are two main cryptographic concepts used in Blockchain, Hashing and Digital Signatures. In general, there are three forms of encryption that are widely used, symmetric cryptography, asymmetric cryptography, and hashing.


A DAO (Decentralized Autonomous Organization) can be thought of as a corporation, which runs without involving human intervention under the control of a trusted set of business rules.

A dApp is a decentralized application that must be completely open-source, must operate autonomously, and with no entity controlling the majority of its tokens.

A MicroChain contract controls the Dapps on the MicroChain. It is available in the release of nuwa 1.0.8 and later.

Decentralisation means the network operates on a peer-to-peer basis. A global network of computers use blockchain technology to jointly manage the database that records transactions instead of one central server.

Decryption is the process of taking encoded or encrypted text or other data and converting it back into text that you or the computer can read and understand. This term could be used to describe a method of unencrypting the data manually or unencrypting the data using the proper codes or keys.

Difficulty refers to the difficulty level to verify blocks in the blockchain network in Proof-of-Work mining.

Digital Signature
Digital signature refers to the digital code, which is generated by public key encryption attached to an electronically transmitted document to check its content and the identity of the senders.
→ See also: Cryptography

Distributed Ledger
Distributed ledgers are a type of database that are spread across multiple sites, countries or institutions. Distributed ledger data can be either “permissioned” or “un-permissioned” to control who can view it.

Double-spending is a potential flaw in a digital cash scheme in which the same single digital token can be spent more than once. Unlike physical cash, a digital token consists of a digital file that can be duplicated or falsified. As with counterfeit money, such double-spending leads to inflation by creating a new amount of copied currency that did not previously exist.


Encryption is the process of turning a clear-text message (plaintext) into a data stream (cipher-text), which looks like a meaningless and random sequence of bits.
→ See also: Decryption, DAO

is an open source platform that can be used by the developers to develop and deploy decentralized apps. The blockchain based decentralized platform is aimed at resolving issues related to censorship, third-party involvement and fraud.

Ethereum Virtual Machine. EVM enables anyone to execute arbitrary EVM Byte Code. Every Ethereum node runs on the EVM to maintain consensus across the blockchain.


Fiat Currency
A fiat currency is a currency that is declared by the government to meet the financial obligation like USD, EUR, CNY, JPY or INR. It means that Fiat is the only currency that can be used to buy, sell or trade goods.

A special operation of MicroChain. Each MicroChain needs to defined the flush period in terms of MotherChain block numbers when it is created. In each flush operation, the status of the MicroChain is written to the MotherChain. In the flush operation, MicroChain will give out the mining rewards to the SCS miners, deposit/withdraw MicroChain tokens, and other transactions that may change the status in the MotherChain.

A fork builds an alternative blockchain version by allowing two blocks to run simultaneously on different parts of the network. Forks generally happen in the crypto-world when new ‘governance rules’ are built into the blockchain’s code. It creates two parallel blockchains, where one among the two is the winning blockchain.
→ See also: Accidental Fork, Hardfork

Fungibility is the idea that every item in a set is worth exactly the same amount. In cryptocurrency, that means that tokens have the same value, regardless of who owns them or what their history is. Fungibility is extremely important to the success of a decentralised network.
→ See also: Non-Fungible Token


Genesis Block
The first block in the blockchain ledger refers to the Genesis Block. Also, the block is hardcoded so that no changes can be done once it is executed. Bitcoin’s first Genesis Block has 50 bitcoins.

The usage of blockchain costs money. The money is used to reward miners who validate transactions and append them to the blockchain. All transactions on the blockchain have a fee associated with it, called GAS. GAS is a unit of complexity that is used to set the price of code execution.


A hardfork is a type of fork that makes previously invalid transactions valid and needs all users to upgrade their clients. On July 21, 2016, the Hardfork that happened in public blockchains was Ethereum Hardfork. It has changed the Ethereum protocol; thus a second blockchain emerged known as Ethereum Classic (ETC) that supports old protocols of Ethereum.
→ See also: Fork

An alphanumeric string, Hash Value is a function that takes an input and output. It is used to do the confirmation of coins’ transactions on the blockchain.

Hashing is the procedure that a miner on a Proof-of-Work blockchain constantly repeats in order to find an eligible signature (aka a proof of work). In other words, it is the procedure of repeatedly inserting a random string of digits into a hashing formulae until finding a desirable output.
→ See also: Cryptography

Hashing Function The hash function transforms the digital signature, then both the hash value and signature are sent to the receiver. The receiver uses the same hash function to generate the hash value and then compares it to that received with the message. If the hash values are the same, it is likely that the message was transmitted without errors.

A hashrate in blockchain and cryptocurrency operations is defined as the number of hash operations done in a given amount of time, or the speed of a miner’s performance. The hashrate is an important factor in the logistics of cryptocurrency mining and blockchain operations, and something that is often evaluated and discussed in cryptocurrency communities.

Hot Wallet
A Hot Wallet refers to a cryptocurrency wallet which is connected to the internet.

Linux foundations hosted the blockchain project known as Hyperledger. An open-source platform, Hyperledger aims to bring collaborative effort from the blockchain experts in the market for the enhancement of Blockchain technology. It comprises various systems and tools for developing open-source blockchains.


Initial Coin Offering is a type of crowd fundings mechanism that is conducted on the blockchain. The core idea of an ICO is to fund new projects by pre-selling tokens to investors who are interested in the project.

Immutability means a block cannot be modified after it is created. In Blockchain, blocks are chained together so that you cannot go back and change the contents of a block without having to change every subsequent block. Depending on the consensus protocol, you cannot change blocks without everyone else agreeing to it. This is sometimes referred to as “mutable by consensus”.

The process of creating a genesis block and associating it with a network is what we call an instantiation. And the chain of blocks that is built on top of genesis block is what we call an instance.




A ledger is an append-only record store, where records are immutable and may hold more general information than financial records.

Lightning Network
It is the best solution to Bitcoin’s inherent scalability issues. It enables payments fastly using Smart Contracts functionality. Also, it allows cross-blockchain payments if both users use the same cryptographic hash function.

Light Node
A computer on the blockchain network that verifies a finite number of transactions relevant to its dealings using SPV (simplified payment verification) mode.
→ See also: Node


Merkle Tree
Merkle tree is a cryptographic hash tree structure that can store a very large amount of data, where authenticating each individual piece of data only takes O(log(n)) space and time. In Ethereum, the transaction set of each block, as well as the state, is kept in a Merkle tree, where the roots of the trees are committed to in a block.


MicroChain Monitor
SCS Monitor is a SCS node monitoring MicroChain status. MicroChain owner can use this SCS node to monitor MicroChain status and get data from MicroChain. Only the owner of MicroChain can add monitors.

Mining is the process by which transactions are verified and added to a blockchain. This process of solving cryptographic problems using computing hardware also triggers the release of cryptocurrencies.

Multi-Signature (multisig) is the addresses that enable several parties to need more than one key to authorize the transaction. These addresses have much higher resistance to theft.


A node refers to any computer connecting to the blockchain network.

Non-Fungible Token
A non-fungible token is a special kind of cryptographic token that represents a unique digital asset, which is not interchangeable. It is in contrast to cryptocurrencies or utility tokens fungible in nature.


An oracle — in the blockchain sense of it — is a software application that verifies real-world occurrences (such as a shipment of banana’s) and submits this information to blockchains. Oracles are basically data transformers and transmitters, converting real-world occurences into data for blockchains.

Off-Ledger Currency
refers to the currency that is minted off-ledger and used on-ledger.

Orphan Block
Orphan blocks often referred to as stale blocks, are blocks that are not accepted into the blockchain network due to a time lag in the acceptance of the block in question into the blockchain, as compared to the other qualifying block. Orphan blocks are valid and verified blocks but have been rejected by the chain.
→ See also: Block, Stale Blocks, Uncle Blocks

On-Ledger Currency
refers to the currency, which is minted on-ledger and utilized like Bitcoin.


P2P (Peer-to-Peer)
P2P, Peer-to-Peer, refers to decentralized interactions held between two parties or more in a highly interconnected network. The participants involved in the peer-to-peer network can deal directly with each other via a single mediation point.

A participant is the person who is responsible for accessing the ledger, reading the records and adding them to the blockchain.

Practical Byzantine Fault Tolerance (PBFT) is an algorithm that optimizes aspects of Byzantine Fault Tolerance (BFT), in other words, protection against Byzantine faults. PBFT has been implemented in several modern distributed computer systems, including some blockchain platforms.
→ See also: Consensus Algorithm

A peer is responsible for maintaining the integrity and identity of the ledger.

PoS (Proof-of-Stake)
An alternative to the proof-of-work system, in which your existing stake in a cryptocurrency (the amount of that currency that you hold) is used to calculate the amount of that currency that you can mine.
→ See also: Consensus Algorithm

PoW (Proof-of-Work)
A system that ties mining capability to computational power. Blocks must be hashed, which is in itself an easy computational process, but an additional variable is added to the hashing process to make it more difficult. When a block is successfully hashed, the hashing must have taken some time and computational effort. Thus, a hashed block is considered proof of work.
→ See also: Consensus Algorithm

PoS/Pow Hybrid
PoS/PoW Hybrid is a combination of Proof-of-Stake (PoS) and Proof-of-Work (PoW) consensus protocols on a blockchain network. Blocks are validated from not only miners, but also voters (stakeholders) to form a balanced network governance.
→ See also: Consensus Algorithm

Private Blockchain
only allows authorized entities to send or receive transactions within the network. No one can write/read or audit the records stored on the private blockchain unless someone has permission to do.
→ See also: Blockchain

Private Key
A private key is a string of data that shows you have access to bitcoins in a specific wallet. Private keys can be thought of as a password; private keys must never be revealed to anyone but you, as they allow you to spend the bitcoins from your bitcoin wallet through a cryptographic signature.

A set of rules that dictate how data is exchanged and transmitted. This pertains to cryptocurrency in blockchain when referring to the formal rules that outline how these actions are performed across a specific network.

Public Blockchain
is an open network which allows anyone from the world to send or receive transactions.
→ See also: Blockchain

Public Key
A public key is your wallet address and is needed by other entities to send you messages or transactions.



is the payment method built on the distributed ledger, which can be used to transfer any cryptocurrency. It consists of gateways and payment nodes that are operated by authorities.
→ See also: XRP

Ring Signature
refers to the cryptographic technology that offers a good level of anonymization on the blockchain. These signatures make sure that individual transaction outputs on the blockchain cannot be detected. Replicated Ledger A ledger that has a one master copy of the data and multiple slave copies.


A change in the scale for handling the demands of the network. It is referred to the ability of the blockchain’s project to manage future growth, network traffic and capacity.

SCS (Smart Contract Server)
Smart Contract Server (SCS) is used to form MicroChains_. It can do MicroChain mining and monitoring. One SCS can form multiple MicroChains.

SCS pool
A pool of SCSs with the same protocol to form one type of MicroChain. The protocol is defined in the SubChainProtocolBase.sol. The SCSs need to register itself into the pool by calling the deployed SubChainProtocolBase contract with paying some deposit. A MicroChain contract using the same protocol can pick up the SCSs and form the MicroChain.

Cryptographic Hash Algorithm. A cryptographic hash (sometimes called ‘digest’) is a kind of ‘signature’ for a text or a data file. SHA-256 generates an almost-unique 256-bit (32-byte) signature for a text.

Sharding is a type of database partitioning that separates very large databases the into smaller, faster, more easily managed parts called data shards. The word shard means a small part of a whole. The method is being researched by Ethereum to increase network scalability.

Smart Contract
Smart contracts are contracts whose terms are recorded in a computer language instead of legal language. Smart contracts can be automatically executed by a computing system, such as a suitable distributed ledger system.

Solidity is a programming language, which is designed to develop smart contracts. Solidity’s syntax is similar to JavaScript and intended to compile into bytecode for (EVM).

Stale Block
Most miners think Stale blocks and Orphan blocks are both the same. No, they are not and do not confuse them. Orphan block are blocks on the shorter chain and as its parent is not known it cannot be validated. Stale block is totally valid and it’s a successfully mined block but they are not active and is not included in the current blockchain.
→ See also: Block, Orphan Blocks, Uncle Blocks

A MotherChain contract defines the protocol for the SCSs to register and form a SCS pool.

A MotherChain contract create the MicroChain by using the SCSs in the SCS pool. It requires the input.


is the second block chain used by developers for testing new versions of client software without putting a real value at risk.

A token is a digital identity for something that can be owned.


Transaction Block
A transaction block is a collection of transactions on the bitcoin network, gathered into a block that can then be hashed and added to the blockchain.

Transaction Fee
All cryptocurrency transactions include a small amount of transaction fee.


Uncle block
Uncle blocks are similar to orphan blocks in Bitcoin but there are some differences. To understand the concept of uncle block consider blockchain as family tree. You, your Dad and his Dad are like “correct” blocks that forms the blockchain. Uncles are closely related to the family and they have their weightage as they are the “correct” next block in the blockchain. However they are not included in the longest chain.
→ See also: Block, Orphan Blocks, Stale Blocks

Unpermissioned Ledger
An unpermissioned ledger means that no one can own these ledgers like Bitcoin have no sole owner. It allows anyone to add data to the ledger and for everyone in ownership of the ledger to have identical copies.


Verification node (VNODE or V-node), is the application that running a full MOAC MotherChain node in the MOAC network. It can mine blocks in the network, transfer moac, perform the POW consensus, and pass MicroChains data in MOAC network.

A MotherChain contract defines the protocol for the VNODEs to register and pass data for MicroChains.

VNODE pool
A pool of VNODEs with the same protocol to pass data of the MicroChain. The protocol is defined in the VNODEProtocolBase.sol. The VNODEs need to register itself into the pool.


Wallet is a file that contains a collection of private keys and communicates with the similar blockchain. Wallets hold keys, not coins. Also, it requires backups for security reasons.

Whisper is a part of the Ethereum P2P protocol suite, which allows for messaging between users via the blockchain network. Whisper’s main task is to provide a communication protocol between dApps.


is the native cryptocurrency for the Ripple distributed ledger payment network that acts as a bridge currency to other currencies.
→ See also: Ripple