Blockchain Glossary

A procedure that is meant to provide increased security of sensitive information in an age of increasing cybercrime. The security protocol calls for both a password and an additional piece of information, often something that is in the physical possession of the user such as a smartphone or credit card.

An attack on the blockchain that results in a group of miners controlling over 50% of the network’s mining hash rate. A term used mostly in reference to Proof of Work coins.

An accidental fork happens when two or more miners find a block almost simultaneously. One chain then becomes longer than the other, and the network eventually abandons the blocks that are not in the longer chain. These blocks are then classified as ‘orphaned blocks.’

An distributed ledger used by two or more parties to negotiate and reach an agreement.

Any cryptocurrency that exists as an alternative to bitcoin.

API stands for Application Protocol Interface, and is an application endpoint that can be triggered and queried to post or get data. The node server application offer API through the peer to peer network.

Often compared to GPUs, ASICs are specially made for cryptocurrency mining and may offer significant power savings.

Atomic swaps involve cryptocurrencies across Blockchains that are tradeable with one another without needing an exchange in the middle.

A distributed ledger providing a durable record of agreements, commitments, or statements, providing evidence (attestation) that these agreements, commitments, or statements were made.

Refers to the token/cryptocurrency.

The first, and most popular, cryptocurrency based off the decentralized ledger of a blockchain.

A collection of transactions that have happened during a certain amount of time. The transactions are bundled in a block and added to the blockchain.

A method of encrypting text in which algorithm and cryptographic key are applied to a data block at once as a group instead of one bit at a time.

An online tool for exploring the blockchain of a particular cryptocurrency, where you can watch and follow all the transactions happening on the blockchain. Block explorers can serve as blockchain analysis and provide information such as total network hash rate, coin supply, transaction growth, etc.

Bitcoin’s supply of new coins issued to miners is cut in half about every four years to keep it scarce. This 50% cut is known as the halving. The next halving will be around 2020.

Refers to the total number of blocks on a given cryptocurrency blockchain. It starts with the first block, also known as the Genesis Block (Height 0) and counts up from there.

Payment made to the volunteers who offer their computers to facilitate transactions on a blockchain network. The payment can be a mix of new coins and transaction fees.

Shows the file size of each block on a blockchain and therefore, how many transactions can be bundled and processed in each one. For Bitcoin, the current block size is 1MB.

A decentralized, unchangeable record of all transactions that have ever happened. It bundles transactions in order on blocks and stores them permanently.

A pseudorandom number computed by hashing together the BlockSeed of the previous block and the Account Address of the new Blocksmith.
Used as a seed for any deterministic random numbers that must be used for this block, such as calculating the SmithTime for all Blocksmiths, computing the PoP Group for this block, and computing the PoP Rewards list.

An account which creates blocks.

An application that runs at browser level used to keep private keys safe, and to interact with the blockchain in behalf of web applications.


Burning coins is the action of sending them to an address where they are irretrievable.

The ability of a network to properly reach consensus at any time, assuming that no more than 2/3 of its actors are malicious. Checkpointing is commonly used alongside to make data stored on the blockchain final.

Consensus algorithm that combines Proof of Work and Proof of Stake. Ethereum is going to use Casper as a transition to Proof of Stake.

Allows for a quick transfer of digital media needed to load internet content (HTML, JavaScript, CSS, etc.) by storing copies in data centers across continents.

A record of transactions which is maintained by the central agency/party/person.

The process of connecting two blockchains with each other, thus allowing transactions between the chains to take place.

A program that initializes and manages a ledgers state through submitted applications. It is the Hyperledger Fabric equal to Smart Contracts.

Classical cryptocurrency mining requires huge investments in hardware and electricity. Cloud mining companies aim to make mining accessible to everybody. People just can log in to a website and invest money in the company which already has mining datacenters.

The “sender” of a special transaction included in every new block (on some blockchains) that creates new tokens from nothing. These tokens are given as a reward to the miner that creates the new block, thereby increasing the total amount of tokens in circulation within the blockchain. Some blockchains use the coinbase only at block 0 and have 100% of their tokens already created when the blockchain is launched. (“Coinbase” should not to be confused with the cryptocurrency exchange from San Francisco of the same name.)

The offline safekeeping of private keys which allow for access to cryptocurrency funds. Typically this is done through hardware wallets, USB drives, and paper wallets.

Hyperledger Fabric command line allowing for administrative tasks.

Generates a rest server and associated API from a deployed blockchain that makes accessing data on blockchain easier by generating REST API service.

When a majority of participants of a network agree on the validity and order of a transaction inside the blockchain ledger.

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.

A point – either in time, or defined in terms of a set number or volume of records to be added to the ledger – where peers meet to agree with the state of the ledger.

A blockchain where a pre-selected set of nodes handles the consensus process. It is also called a permissioned blockchain network that can be a hybrid model built between the trusted entity model of private blockchains and low trust provided by the public blockchain.

Also known as tokens, cryptocurrencies are representations of digital money.

A function that returns a unique big number that is commonly represented as fixed-length string. The returned string is unique for every unique input. Used to create a “digital ID” or “digital thumbprint” of an input data(bits).

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

An unauthorized use of a device owned by others, to mine cryptocurrency. The first widely known attempt for cryptojacking was the torrent tracker Piratebay. They enabled an in-browser mining software, so when somebody visits the website, his/her computer will start mining cryptocurrency via the browser with no indication of it happening.

A method for decentralized funding of projects. It combines ideas from Decentralized Autonomous Organizations (DAOs) and Initial Coin Offerings (ICOs). Project investors have the ability to vote and, if dissatisfied with the progress of the project, could get their money back.

A corporation that runs without any human intervention and surrenders all forms of control to an incorruptible set of business rules.

Applications that run without the control of a central authority (like a software company or government)

A peer-to-peer layer of the Internet that can only be accessed with special software. It is known as Darknet because it often involves illegal marketplaces and illicit activity.

A special system to store data in the blockchain.

A denial-of-service attack is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet.

A peer-to-peer exchange that allows users to buy and sell cryptocurrency and other assets without the control or fees of a central authority.

An organization that operates and coordinates work without the control of a central authority like person, company, or the government.

The process used to turn cipher-text into plain text.

A delegated model where those with a stake don’t buy a lottery ticket to be able to create blocks, but they use them to vote and elect witnesses.

Refer to the first step in the Blockchain 3 layer model. They are a set of concepts or properties that you wish your smart contract to have. These include Distribution, Decentralization, Immutability, and Peer-to-Peer.

Any text or media that is formatted into binary data.

Paperless money that is stored on computers of Private/Public institutions to replace cash.

Anything used by friends or institutions to identify you online, such as email address/Twitter handle, etc. On the blockchain, when you sign something (with the private key), you are also proving your identity.

A digital code generated by public-key encryption that is attached to an electronically transmitted document to verify its contents and the sender’s identity.

A system that is not controlled and cannot be changed by a central authority like a person, company, or the government.

A problem in which somebody fraudulently sends digital money to two different receivers (even though they only have enough for one transaction).

A non-fungible Ethereum token standard. Non-fungible meaning that the token standard is used to represent a unique digital asset that is not interchangeable.

The process of turning the plain-text into a data stream (cipher-text).

A token that represents an ownership interest in a company. Equity tokens work similar to traditional stocks and may include voting rights.

Stands for Ethereum Request for Comment followed by the assignment number. A technical standard for smart contracts the majority of Ethereum tokens follow.

A token standard with a focus on security that allows token transfers to act as ETH transactions, using event handling (transaction management) to prevent lost tokens. This standard is an improvement on the ERC20 critical bug.

The digital currency of the Ethereum network.

A platform for creating and running smart contracts. These are programmable applications that run exactly as promised – without downtime, censorship, or interference.

A turing complete virtual machine that allows anyone to execute arbitrary EVM Byte Code. Every Ethereum node runs on the EVM to maintain consensus across the blockchain.

A variable number to which set fees needs to be multiplied by, to give an adjusted fee amount to be paid for transactions. Operators of registered nodes on the network may take a regular vote on the appropriate multiplier, which we call the fee scale, for minimum transaction fees. This guarantees that while the value of the blockchain token may fluctuate, the fees to be paid for transaction remain stable against regular currency.

A term used to describe traditional government-issued and backed currencies like dollars, euros, and yen. Not backed by physical commodities but by legal tender laws.

Forks create an alternate version of the blockchain, leaving two blockchains to run simultaneously on different parts of the network.

Fungible means that a given good is identical (a.k.a., interchangeable). In crypto, we often talk about fungible or non-fungible tokens. A fungible token is Bitcoin. One Bitcoin is and will always be one Bitcoin, just like any other Bitcoin.

To run decentralized applications and smart contracts on the Ethereum network, apps calculate their usage using an internal pricing unit called Gas. Actual fees are then paid in Ether.

The very first block of a blockchain.

A type of fork that makes previously invalid transactions valid and needs all users to upgrade their clients.

A physical storage device for private keys that uses special technologies to protect access to the keys so that they do not get misused.

A function that takes an input and outputs an alphanumeric string known as the “hash value” or “digital fingerprint.”

The number of hashes that can be performed by a bitcoin miner in a given period of time (usually a second).

The world’s first fast, secure and fair distributed ledger, Hedera Hashgraph can perform 500,000 transactions per second. It is a directed acyclic graph that has the properties of the DLT and doesn’t need Proof-Of-Work like blockchain-based platforms.

Transforms the input data into a hash value that is sent to the receiver as a digital fingerprint. 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/stored without errors.

A cryptocurrency wallet which is connected to the internet and immediately available for transactions.

A hybrid PoS/PoW allows for both Proof of Stake and Proof of Work as consensus distribution algorithms on the network.

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.

lockchain Application Development framework which simplifies the blockchain application development on Hyperledger Fabric.

Hyperledger project hosted by Linux which hosts smart contracts called chaincode.

“Unable to be changed”. Data stored in a blockchain system is unable to be changed after it is written/solved (not even by administrators).

A public, crowdfunded sale of cryptocurrency tokens to raise money for a project.

Initial Token Offerings are similar to ICOs (initial coin offerings), but different in that not every blockchain project that is tokenized has developed a new coin.

Helps to reverse and repair the damages related to hacking or a catastrophic bug on a blockchain.

Distribution protocol that started as an open source project at Interplanetary Networks. The p2p method of storing and sharing hypermedia in a distributed file system aims to help applications run faster, safer, and more transparently. IPFS allows objects to be exchanged and interact without a single point of failure. IPFS creates trustless node interrelations.

A type of cryptographic hashing function. Ethereum uses Keccak-256.

An immutable store of records that can only be appended (added to). Blockchains use decentralized ledgers as their core technology.

A popular hardware wallet, designed and sold by the French company Ledger Wallet.

A computer on a blockchain network that only verifies a limited number of transactions relevant to its dealings, making use of the simplified payment verification (Bitcoin SPV) mode.

A proposed feature extension to the Bitcoin’s Blockchain technology that’s designed to facilitate faster transactions and better scaling by off-chain agreements.

The property of linkability allows one to determine whether any two signatures have been produced by the same member (under the same private key). The identity of the signer is nevertheless preserved. One of the possible applications can be an offline e-cash system.

The chain of blocks that prevails in the case of a fork (see “Fork”, above.) When miners “chain” a new block to the previous one, the way the blocks are “chained” has a value. The harder the work done in chaining a block (in PoW blockchains), or the closest a block complies to the consensus rules, the higher the score is for that piece of the chain. In the event of a fork, when a node has more than one new block or blockchain to choose from to update itself, the node calculates the cumulative “score” generated when creating each chain, and chooses the chain with the highest score (in Proof of Work this “score” is referred as “difficulty”, and the chain with the highest cumulative difficulty is the chosen one.) In this way, nodes in a P2P network can reach the same decision without communicating with each other, but simply using the same algorithm to evaluate the options presented to them.

A blockchain with high frequency block creation (one per minute, or even one every 20 seconds)

A full node that keeps the full copy of the blockchain in real-time but has additional roles such as participating in governance and voting. On cryptocurrencies with masternodes such as DASH, they are a key component to the functioning of the blockchain network.

A temporary cache of transactions stored by a node that will exist until each transaction is incorporated into the blockchain. When users submit a transaction to the P2P network, each node receives and validates the transaction and, before rebroadcasting it to the rest of the network, keeps a copy of it in a local queue called a “mempool”. Once the transaction is included in a new “chained” block, the node first executes the transaction, updating the status of its copy of the blockchain, and then removes the transaction from its mempool.

A transaction broadcasted to the P2P network that has been validated and it is in queue to be included in a block.

The cryptographic hash of all hashes in a Merkle tree. In a blockchain, this is a merkle hash of all transaction hashes in the chain.

A system that splits complicated hash code functions into smaller chunks (creating a tree-like shape). This allows faster verification on large-scale blockchains.

An important participant in the blockchain network, who bundles transactions and gets paid in new coins and transaction fees in return for helping to run the system.

The process by which transactions get verified, bundled, and added to the blockchain.

A group of people or organizations who come together to pool and share their computer resources for cryptocurrency mining.

The payment resulting from volunteering computer resources to process cryptocurrency transactions.

A computer setup that’s specially designed for mining a cryptocurrency.

Browser for installing and using Dapps.

A Hyperledger Fabric blockchain network can be governed by one or more MSPs.

The method to require more signatures to authorise a transaction. One or more than one out of n signatures can be required based on the multisignature setup.

A currency that has no history recorded on a ledger of when it was minted, or how it has changed hands, but is later on represented as tokens on the blockchain, e.g., Fiat currency.

A system for managing and implementing changes to a cryptocurrency blockchain.

A digital currency that is originally originated on the ledger, e.g., Bitcoin.

Collaborative and open software development approach that encourages experimentation and sharing.

An external data feed/source of info coming from outside the blockchain from the real world. Oracles work as a bridge between the real world and the blockchain by providing data to the smart contracts.

A computer network that allows nodes to share resources.

A type of cold storage where private and public keys (and often a QR code) are printed or written on physical paper to prevent hacking and theft.

The ordering of all nodes in the registry used to assign a set of preferred peers to each node. Each node compute its peer filter, and connect to the assigned nodes. When a node publishes receipts, the receipts it is allowed to publish must come from one of its assigned peers at the time the receipt was created.

A peer-to-peer network that distributes computing tasks among many, private computers (decentralized servers), instead of using company computers (centralized servers)

Similar to a ledger (see above) but designed with restrictions, so that only a select group of people or organizations have permission to access the full features.

A ledger (see above) that doesn’t require the approval of a central authority to be used. It is not owned by anyone and open to participation. A good example is Bitcoin itself.

A ledger (see above) that doesn’t require the approval of a central authority to be used. It is not owned by anyone and open to participation. A good example is Bitcoin itself.

A set of roles, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates and manage public-key encryption.

The Lightning Network concept implemented on the Ethereum blockchain.

Only allows authorized entities to operate or participate within the network. E.g., just like a private road has access only for the authorized members.

A string of letters and numbers that are used for sending cryptocurrency. The private key should be kept secret because it enables spending with the cryptocurrency wallet.

Proof of Authority (PoA) is a reputation-based consensus algorithm that leverages the value of identity and reputation of block validators which means that block validators are not staking coins but their own reputation, instead.

The term “Proof-of-authority” was first proposed and put into use by Gavin Wood, co-founder of Ethereum and Parity Technologies.

Here are the key take aways from the Whitepaper

How Does It Work?

  1. PoA consensus is based on an extensible group of independent validators and each of them NEEDS to have a verifiable license to be authorized as a validator by the Master of Ceremony. (“authority” comes from them being thoroughly inspected before being accepted as validators, having to satisfy all of the stringent requirements.)
  2. During the initiation ceremony, the MoC invites this set of trusted entities to participate in the network by sending an initial key known to the network via a tamper-proof secure channel.
  3. Validators start to create blocks and generate a reward for the network security. When a validator creates a block, it is rewarded(Not in all cases. Rewarding mechanisms may be different for different use cases.) with a coin and all transaction fees.

So WHAT are the Pros of a PoA;

  • Since it relies on a limited number of block validators, it is highly scalable and transaction time is faster.
  • Having said that, in both cases, POW and POS, those who are the most resourceful win the right to write or to mine the block, to write the history whereas, in PoA all of the *verified validators have an equal chance and take turns to validate the blocks.

The Cons of a PoA network?

  • It foregoes decentralisation, It in simple words, is just an effort to make centralised systems more efficient.
  • PoA is also highly prone to censorship and blacklisting.
  • Reputation doesn’t systematically prevent malicious behaviour, the size of the gains, that can be gathered with a reputation-destroying event can be more valuable than the reputation in community.


  • All consensus mechanisms DON’T have the same rewarding mechanism. Deciding who validates the block is the only thing that remains constant. Eg:- There are PoS implementations that not only reward with transaction fees but with the token rewards as well.
  • Each validator in a Proof Of Authority(PoA) consensus protocol has equal rights to create a block.

Similar to the Proof of Work, but instead of computing resources, Proof of Capacity leverages available disk space (storage). This is less vulnerable to specialised hardware allowing mining groups to centralise the network.

So how does Proof of Capacity work?

  1. Proof of Capacity uses a very slow hash known as Shabal, since hashes are hard to calculate, they are supposed to be precomputed and stored in a hard drive. This process is known as plotting your hard drive.
  2. When plotting, nodes create something called nonces. Nonces are created through repeated hashing of data. The more hard drive space a node allocates to plotting, the more nonces it can store.
  3. During mining, the node calculates a scoop number which gives a scoop data to calculate the amount of time, called a deadline. This process is repeated for all the nonces on the nodes hard drive. The deadline represents “the number of seconds that must elapse since the last block was forged before you are allowed to forge a block. The lowest deadline submitted to the network forges the block.
  4. The node that forges the block claims the block reward.

PoC is used byBURSTPoC was first publicly implemented into a cryptocurrency with BurstCoin, founded in August 2014. Burst claims to favour smaller miners by design, making transaction costs cheaper and the network more decentralised.CHIAChia is an upcoming cryptocurrency developed by the creator of BitTorrent. It’s based on both proofs of capacity and time. Chia was released in the last quarter of 2018STORJStorj is a Amazon S3-like cloud platform that uses a blockchain to store data. It uses proof-of-capacity to both mine and store data.SAFESAFE is a decentralised web platform based on the PoC blockchain. It uses a variant of proof-of-capacity known as proof-of-resource to verify the farmer is holding the data and supplying when needed.

The Proof of Participation consensus equally distributes decision power and rewards amongst every node in the federation that contributes to a blockchain’s operation. The protocol only lets new people into the federation slowly (and prioritizes those willing to stake the most). It measures the “participation” of nodes by whether they are rebroadcasting transactions and blocks, and kicks out the nodes that aren’t doing their job.

Miners still process and validate transactions, but do so by proving that they have ownership of a certain amount of the asset, rather than by performing energy-intensive computations.

In PoW, miners solve difficult problems to create blocks. PoW runs on a system of “the longest chain wins.” So assuming most miners are working on the same chain, that one will grow fastest will be the longest and most trustworthy. Hence Bitcoin is safe as long as more than 50% of the work being put in by miners is honest.

A set of rules that dictate how data is exchanged and transmitted.

A network on the global internet allowed to participate in all available transactions and participate in the consensus protocol to help determine who gets to add blocks on the chain and maintain the shared ledger. E.g., just like a public road has open access to anyone.

A string of letters and numbers that are used to receive cryptocurrency. Works similar to a traditional bank account number and can be shared publicly with others.

A cryptographic system that uses both a private key and public key to safeguard transactions.

An upcoming protocol change to the Ethereum blockchain that is designed to allow for high-speed transfers and better scaling. Similar to Bitcoin’s proposed Lightning Network.

Refers to a method that allows a sender to replace a “stuck” or unconfirmed transaction with a new one that uses a higher fee. This is done to make sure a transaction confirms as quickly as possible. The “replacement” transaction uses the same inputs as the original one. This is not considered a double spend, as the receiving address(es) typically remain the same.

To measure a node’s participation in ZooBC, when exchanging information in the Peer to Peer network, nodes acknowledge having received information from another node by sending back a digitally signed receipt. Once a node has collected enough receipts and is its turn to create a block, it can include in the metadata of the block a subset of the receipts it has collected. This can be later used to prove, at consensus level, that the node has in fact participated in the network, thus earning participation score.

A type of digital signature that can be performed by any member of a group (1-of-M). One of the security properties of a ring signature is that it should be computationally infeasible to determine which of the members’ keys was used to produce the signature.

A real-time gross settlement system, currency exchange, and remittance network created by Ripple Labs Inc. Ripple is built upon a distributed open-source protocol and supports tokens representing fiat currency, cryptocurrency, commodities, or other units of value such as frequent flier miles or mobile minutes.

The work a node does to replace the last blocks when it realises to be in a fork of the blockchain as it receives a new chain that’s longer (has higher cumulative difficulty) than its current active chain. Reorganisations happen when a node realises that what it thought was the canonical chain turned out not to be. When this happens, the blocks in the latter part of its chain (i.e. the most recent transactions) are reverted and the transactions in the newer replaced blocks are executed. All reorgs have a “depth,” which is the number of blocks that were replaced, and a “length,” which is the number of new blocks that did the replacing.

Bitcoin’s existence began with an academic paper written in 2008 by a developer under the name of Satoshi Nakamoto. Satoshi is the name used as the original inventor of Bitcoin.

The ability of the blockchain project to manage future growth, network traffic, and capacity in anticipation of future demands.

Schnorr proposes to give users a new way to generate the private and public keys critical to cryptocurrencies. It replaces the Elliptic Curve technique currently used to generate keys with the Schnorr technique. This update increases both privacy and security by grouping together MultiSig and regular transactions in the same category, allowing the blockchain process to more transactions and hiding whether or not a transaction is MultiSig or not.

SDK stands for Software Development Kit. It is a set of libraries and tools for various programming languages that are used by developers to implement applications that interact with the blockchain

An important Bitcoin protocol that removes the signature information, otherwise known as the ‘witness information’ and storing it outside the base transaction block. It enables a greater number of transactions to fit within a block. It also makes the lightning network and better scripting possible.

A family of cryptographic hash functions published by the National Institute of Standards and Technology (NIST) as a U.S. Federal Information Processing Standard (FIPS). A cryptographic hash function is special because it maintains certain desirable properties vs. a non-cryptographic hash function.

A very strong cryptographic standard that is used as the basis for Bitcoin’s and other Blockchains.

A scaling solution for blockchain such that instead of every other node holding a full copy of the Blockchain data, they only own partial copies.

Emerging mechanisms that allow tokens and other digital assets from one blockchain to be securely used in a separate blockchain and then be moved back to the original blockchain if needed. Sidechain functionality holds tremendous potential to enhance the scalability of existing blockchains.

The cryptographic result generated by the data that needs to be signed and the private key of the user signing it, used to prove authenticity and origin of the data.

A now-defunct marketplace on the Darknet (see above) that was shut down by the FBI. It was best known for selling drugs and other illegal products and accepting Bitcoin as a form of payment.

Self-running computer code that enforces a set of pre-set rules that later cannot be changed, therefore this is like a contract between two or more parties that is enforced digitally on the blockchain.

The maximum time after the previous block that can be waited for a new block to be created.

After this time, all remaining Blocksmiths can legally submit a block to the network, regardless of their computed SmithTime.

The scaling factor which is multiplied into an account’s SmithTime calculation.

When new blocks are being broadcast too frequently, it is increased; when new blocks are too slow, it is reduced.

A psuedorandom number, computed from the BlockSeed of the previous block and the Account’s address, which is used to calculate the SmithTime

The time (in seconds) after the previous block when this Blocksmith is allowed to publish a block to the network

A change to the rules of a blockchain protocol that are backward compatible with previous rules but creates a temporary divergence in the blockchain network.

A computer programming language that is used to develop smart contracts and decentralized applications on the Ethereum platform and other blockchains.

A sequence of blocks to shortcut from the genesis block to a snapshot without going through each block, and yet having cryptographically secure current data.

A user’s funds that are locked or held as guarantee. Mostly referred in “Proof of Stake” blockchain, the stake is the economic purpose to provably commit to a promise that the user won’t sell the staked tokens for a pre-established period of time.

A Sybil attack is a kind of security threat on an online system where one person tries to take over the network by creating multiple accounts, nodes or computers. For example a Sybil attack can take place when somebody runs multiple nodes on a blockchain network. Attackers may be able to out-vote the honest nodes on the network if they create enough fake identities (or Sybil identities). They can then refuse to receive or transmit blocks, effectively blocking other users from a network.

A set of tools that emulates full deployed peer to peer network of nodes, and stage sparticular events in order to test new functionalities (consensus rules, transaction types, signatures integrations) and possible attack vectors to the blockchain before publishing the code to the live environment.

Unlike standard “t-out-of-n” threshold signature, where t of n users should collaborate to decrypt a message, this variant of a ring signature requires t users to cooperate in the signing protocol. Namely, t parties (i1, i2, …, it) can compute a (t, n)-ring signature, σ, on a message, m, on input (m, Si1, Si2, …, Sit, P1, …, Pn).

A unit of value within a blockchain system, at times used by users as an internal currency to pay for goods and services, but essentially needed to pay the transaction fees. The financial value of tokens is determined by their current market value which in turn depends on the level of user’s trust into the blockchain.

Refers to a distributed blockchain system that doesn’t require a native digital currency (or unit of value) to function and to pay for transactions.

A protocol to store files in a distributed manner in a peer to peer protocol. (A protocol to distribute and store files by using a peer to peer network)

In addition to the previous scheme, the public key of the signer is revealed (if they issue more than one signatures under the same private key). An e-voting system can be implemented using this protocol.

A transaction is a set of instructions that a blockchain user prepares and signs in a client application. The user then broadcast the transaction to the network. Nodes in the network receive the transaction, execute it, and incorporate it with others into a block.

The part of the transaction that includes the informations relative to the transaction (excluding metadata in the header and signatures in the footer).

The payment a user grants to the network to include her transaction in the blockchain. To submit a transaction a user needs to add a fee that is given as an incentive to nodes to maintain the blockchain. The fee is usually attached to the transaction itself; if the transaction is rejected the fee is usually returned to the user. Fees also serve as a deterrent to users from spamming or otherwise abusing a blockchain.

Blockchains are trustless because no participant needs to trust any other participant for transactions to work out. Trust comes from the system itself, which is impartial.

Refers to the ability of smart contracts or scripts on a Blockchain to perform calculations and enforce complex rules that most general-purpose programmable computers are currently capable of. This means that the programming language should support (or emulate) features such a conditional branching and storing-data-in-memory in order to satisfy Turing’s concept of a complete machine. In the past, not all computers, even those that are programmable (e.g., Casio calculator) are Turing complete. Not all Blockchains have virtual machines that are Turing complete, even if they do support some form of scripting or smart contracts.

A token that grants owners access to useful products or services on the Blockchain, thus providing utility to its owners.

Certain blockchain systems such as Bitcoin use the UTXO model. In this model, the Unspent Transaction Output describes some digital money that has been sent from one wallet address to another but has not yet been “spent” by the receiver (i.e., transferred from the receiver to somebody else). Therefore, the outputs of a blockchain transaction are represented as different unique notes/bills (e.g., $1 or $10 bill), and this helps prevent double-spending each UTXO or “digital note” is accounted separately by such a blockchain system.

A cryptocurrency public address (see above) that includes custom letters and numbers that are human-readable. An example would look like 1r4523COINCOIN7u01174234kf.

Cryptocurrency transactions are confirmed at regular intervals. New transactions have zero confirmations, which means they have not been verified yet and are less reliable.

In cryptography, it enables one party to provide evidence that something happened to another party – all without revealing private details.

The ZooBC coin. 1 billion Zoo will be created by the coinbase in a long range of time (50 years?).

The smallest portion of a Zoo. It takes 100’000’000 ZooBits to make a Zoo. That is one hundred million ZooBits for a Zoo.

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