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This page lists terms, expressions, and concepts you will find in the Alphabill documentation.



Alphabill's native currency and transaction token. There is an initial supply of 10 billion ALPHA. The ALPHA token has the following purposes: a) it enables the proof of stake mechanism, and b) it is used as means of payment for services on network.

AVL tree

Adelson-Velsky and Landis (AVL) tree is a self-balancing binary search tree used in Alphabill, where the nodes of the tree are either tokens or smart contracts.

Atomicity Partition

An atomic swap is an exchange of cryptocurrencies from separate blockchains. The swap is conducted between two entities without a third party's involvement. The idea is to remove centralized intermediaries like regulated exchanges and give token owners total control. In Alphabill, a dedicated Atomicity Partition provides this functionality, allowing decentralized exchanges to be separate from the settlement operations.



The Alphabill blockchain is built using bills as transaction units. In a bill-based money scheme, such as physical cash, the only thing that changes during a payment is the ownership of the bill.

Bills are serialized with a unique identifier (used as the sorting/searching key in the AVL tree), and a transaction order changes ownership of the bill—they are not marked as spent. As no checks or coordination is needed, the bills can be on different machines and processed independently in parallel.


A set of validated transactions on the network, grouped together for mostly efficiency reasons. Blocks contain cryptographic information from previous blocks, and also new transaction data.



A data structure used within Alphabill that contains elements that enable an interested party to verify claims about a unit's state or about a transaction's execution. The design of the Alphabill state tree allows four different types of certificates to be created: proof of uniqueness, proof of unit state, proof of transaction execution, and proof of transaction non-execution.

In Alphabill, certificates are created on-chain and potentially used off-chain.


A procedure used by a blockchain network's nodes to agree on the validity of transactions accepted onto the network. Alphabill has a single consensus instance across the network such that deterministic finality is achieved across the network within one block.


decentralized application (dApp)

Applications that run on a peer-to-peer (P2P) network of computers rather than one central computer. This allows the software to run on the internet without being controlled by a single entity.

decentralized finance (DeFi)

A blockchain-based form of finance that removes the need for intermediaries such as banks, and uses smart contracts to settle deals between parties.

delegated proof of stake (DPoS)

A blockchain verification and consensus mechanism where a stakeholder that does not want to run a validator themselves can appoint a validator as their representative and each validator gets selected in the PoS process proportionally to the sum of the stakes that it represents.

In Alphabill, the Root Chain consensus is based on DPoS, but with massively reduced computational load, because the Root Chain validators only have to come to consensus on the cryptographic summaries submitted by shard validators, not on individual transactions.

deterministic finality

There are three types of transaction finality: probabilistic, deterministic, and economic finality. Alphabill provides deterministic finality, where nodes run a consensus protocol (in the narrower sense of "consensus" from distributed systems research) to reach agreement on and finalize every block. The low-level consensus protocol is based on HotStuff optimized for latency not throughput (as the Root Chain does not need to validate client transactions).


Development network that provides safe playground to test Alphabill capabilities on a local machine.

double spending

An event where an entity spends the same cryptocurrency token more than once.

Double spending is impossible by the design in the Alphabill model. Each token has a unique address, and there can only be one proof of uniqueness per round, assuming the hash function used is collision-resistant.

dust collection

A procedure where several smaller bills are replaced by a single bill having the same total value. This reduces the number of tokens in the system, which translates into better performance for the network and also reduces the amount of storage needed by user wallets.

Alphabill uses an inbuilt swap mechanism to allow users to reduce the number of bills their wallet needs to hold.



The standard protocol for the issuing and implementing of tokens on the Ethereum blockchain since 2015. ERC stands for "Ethereum Request for Comment" and is followed the standard's assigned number.

EVM Partition

The EVM (Ethereum Virtual Machine) Partition is the native smart contract partition. This partition enables developers to deploy Solidity programs, however, this partition is not shardable. For scalability, the Alphabill architecture allows multiple EVM partition instances to operate in parallel. Smart contracts deployed in different EVM partitions do not share memory and cannot call each other directly. Interoperability is enabled by exchanging proofs which can be verified due to the common root of trust.



A service that allows users to provide their wallet's public addresses and receive a standard amount of test tokens into their wallets to experiment with Alphabill testnet features.

The faucet service supplies fungible tokens of a predefined "user-defined" type in addition to Alphabill's native tokens (ALPHA).

fungible token (FT)

A type of cryptographic token that is non-unique and divisible. The most important property of a fungible token is the amount or value that it represents. A fungible token can be split into several smaller tokens of the same type so that the sum of the values of the resulting tokens is equal to the value of the original token.


Governance Partition

The role of the Governance Partition in Alphabill is sixfold: a) on-chain governance, b) partition management, c) validator assignment, d) network capacity management, e) validator reward handling, and f) software certification.



The output of a hash function. A hash function takes a variable-length message as input and produces a fixed-length hash value as output.

A cryptographic hash function has to be one-way and collision-resistant. One-wayness means it's infeasible to recover the input data from the hash value (or to retroactively create an input producing a given output). Collision-resistance means it's infeasible to find two inputs that map to the same output.



Includes keys that can be used in scripts to create and verify signatures.

key pair

A set of two keys: a public verification key and a private signing key. These keys are used to process and approve transactions within the blockchain. The public key is the address used as a sending or receiving address in a transaction. The private key is the secret that controls access to assets.


layer 1

The main blockchain ledger that operates on the underlying consensus protocol. This layer includes protocol parameters that control capabilities such as scalability and throughput. The most popular layer 1 (L1) blockchains are Bitcoin and Ethereum.

Alphabill is a layer 1 blockchain based on bills to enable public token infrastructure.

layer 2

An additional, off-chain protocol that works on top of the L1 blockchain. The most common solutions are state channels, sidechains, optimistic rollups, and zero-knowledge rollups.


A database of assets and their transactions. It is updated periodically in rounds or blocks that contain a set of transactions. A blockchain is a form of public ledger.



A blockchain protocol that offers users the possibility to send and receive digital assets. Unlike testnet, mainnet is fully developed and deployed for the end user.

Money Partition

The Alphabill Money Partition manages the Alphabill's native currency (ALPHA).



A participant on a blockchain network that communicates with other participants to ensure the security and integrity of the system.

non-fungible token (NFT)

A type of cryptographic token that represents a unique digital or real-world asset. The main characteristic of non-fungible tokens (NFTs) is that they have distinct identities and, in general, even two tokens of the same type are not interchangeable, even though they may share some characteristics as a result of inheritance. Because of that, non-fungible tokens cannot be split or joined.



Any transactions, data, or activities that occur outside of the blockchain network itself. Off-chain activity is typically conducted through secondary channels or networks that are not directly recorded on the blockchain but may still be related to the blockchain in some way.

In Alphabill, tokens can be minted on-chain, then verified and acted upon off-chain, even offline.


Transactions, data, or activities that occur directly on the blockchain network itself. When a transaction or any other operation is conducted on-chain, it means that it is recorded and permanently stored on the blockchain, becoming an immutable part of the distributed ledger.

optimistic rollup

A scaling approach for Ethereum that involves moving computation and state storage off-chain.

owner predicate

In general, ownership of each token in Alphabill is controlled by an owner predicate. The predicate is a function that receives as inputs a transaction order and the current state of the unit that the transaction targets. The function returns a decision whether the transaction should be accepted or rejected.



A system's ability to allow multiple actors to progress on their tasks simultaneously without interfering with each other.

The parallelism of Alphabill allows for different trust models to be selected by users. Every user can independently audit the individual token histories that they have ownership of. They can store not just the private key that controls transfer of the token but also the token ledger itself. This is similar to physical cash—consumers care only about the verifiability of the cash inside their wallets, not that of everyone else in the economy.


Partitions are logical divisions of the state space—each partition may have a completely different transaction system, fee structure and block time. Examples include the Governance Partition, Alphabill Money Partition, Atomicity Partition, User Token Partition, and EVM Partition.

partition node

A computer participating in a partition.

payment order

In Alphabill, every bill has an "owner" that can change when the bill is transferred. When the owner wants to transfer a bill, they do so by sending a payment order that contains two important elements: unlock script and new predicate.

peer-to-peer (P2P)

Network architecture where nodes are connected directly and share workloads or resources without relying on a centralized server.


In general, a function returning a Boolean value (true or false). Its code is stored in the bill's state, and it defines the conditions under which the bill can be transferred.

Predicates are used in the User Token Partition to enable the customization and programmability of tokens, similar to Bitcoin locking and unlocking scripts. There are many types of predicates used in Alphabill and their use together with object-oriented inheritance enables a rich ecosystem of tokens to be developed.

proof of stake (PoS)

A cryptocurrency consensus mechanism used to validate transactions through randomly selected validators, where each validator's chances of being selected grow in proportion to their investment in the system.

proof of work (PoW)

A cryptocurrency consensus mechanism which requires a user to "mine" or solve a complex mathematical puzzle to validate a transaction.


Root Chain

Alphabill's Root Chain is based on delegated proof of stake (DPoS), but with massively reduced computational load. Instead of client transactions, the Root Chain validators only process aggregate summaries from shards. They effectively check the results of the shard validators and confirm they are in coherence. The Root Chain generates Unicity Certificates for identified partitions.


A round consists of achieving consensus on a block of transactions and their execution results. All partition nodes and Root Chain nodes operate in rounds (also known as views). One round may have multiple phases.



The ability of a system to handle more and more work. This is a vital property for a blockchain or it will become slower and more expensive to use.

In Alphabill, parallel decomposition allows each token in the system to be independently updated and verified in parallel. This in turn enables practically unlimited throughput where a single consensus instance provides linear scalability, without sacrificing security, decentralization, or performance.

seed phrase

A seed phrase or mnemonic seed is a collection of words that can be used to re-generate a private key and thus gain control of the assets protected by that key.


Shards are sets of validators, all of which have the same validation rules used to process and store subledger blocks. All machines in all shards participate in a single consensus instance in coordination with validators on the Root Chain. The shards provide bulk transaction validators, state-keeping, ledger handling, and smart contract execution.

Sharding means dividing the network into several smaller component networks that can process transactions in parallel.

smart contract

Smart contracts are programs written to self-execute when certain predetermined conditions are met.

Existing smart contract platforms enable programmability through a shared state model. However, a shared global state cannot scale beyond a single machine. Alphabill uses a new paradigm for smart contract composability—certified message passing without direct inter-shard communication.

state tree

The Alphabill state tree is operated by a network of machines which is decomposed into partitions which operate subtrees of the overall state tree. Each subtree manages a set of tokens. The state tree is built recursively allowing for independently verifiable blockchains to be extracted for each individual token. This allows tokens minted on the blockchain to be verifiable and actionable off-chain in the real world.



Smallest unit of ALPHA that can be recorded on the blockchain. It derives its name from the Greek word "τεμάχιο", which means "fragment" or "fraction". Similarly, Bitcoin uses the term "satoshi" to describe the smallest unit of its currency.
1 tema is equivalent to 0.000'000'01 ALPHA (or 10-8 ALPHA).


A prototype network where users can experiment with the new features and code to provide feedback before a live mainnet launch.


A digitally transferable asset. A token can be fungible (tradable) or non-fungible (unique), and act as a payment unit, reward, trading asset, or information holder.

In Alphabill, tokens are first-class citizens, meaning that each token in the system (either Alphabill's native tokens or the equivalent of ERC-20 user-generated tokens) can be updated and verified in parallel, but with a single consensus protocol that generates a single proof of uniqueness for the entire ledger, once per block.

The main advantage of using tokens instead of accounts in Alphabill is sharded parallelism of production and verification.

token minting

The process of generating tokens.


The process of representing real-world assets with digital tokens.

transaction (tx)

The process of sending or receiving assets on the blockchain.

Transaction Execution Certificate

A proof that a transaction is in a certain block of the blockchain.

Transaction Non-Execution Certificate

A proof that a transaction is not in a certain block of the blockchain.

transaction system

A set of rules and logic for defining units and performing transactions with them.

transaction validator

Executes transactions and generates new blocks.


Unicity Certificate

A proof that the ledger is unique. Generated by the Root Chain. The Unicity Certificate can then be transported across shard boundaries, interpreted, and acted upon by smart contracts on different shards.

Unit Certificate

A proof that the unit (such as a token or a smart contract) has certain attributes (for example, ownership) in the state tree.

unlock script

Creates inputs to the predicate and proves that they have the right to transfer the bill.

unspent transaction output (UTXO)

A transaction output that can be used as input in a new transaction. All existing blockchain protocols use either UTXOs or accounts as transaction units, whereas the Alphabill blockchain is based on bills (similar to physical cash bills).

User Token Partition

In this partition, users can create their own tokens. Alphabill supports user-defined tokens as first-class citizens, offering a flexible framework for defining custom token types, creating tokens of these types, and transacting with such tokens. For more information, see User Token Partition.

user-defined partitions

Any application—whether Web2 or Web3—can participate in the Alphabill economy. The application can request a partition ID, receive and verify tokens, and then generate proofs to reallocate those tokens based on the application logic. For more information, see User-Defined Partitions.



A logical node, operated by a single responsible entity. Due to the composable design of Alphabill, there are three distinct types of validators, all processing part of a single global state tree: transaction validators, root validators, and governance validators.

Verifiable Data Partition

This partition registers hash values, stores them into the ledger, and issues timestamps—proofs that a piece of data existed (was registered) at certain time. Verifiable Data Partition is no longer in use as a separate partition, the functionality is now part of the User Token Partition.



Software to manage cryptocurrency balances and make transactions. Alphabill's native currency ALPHA has its own browser extension wallet based on Web3, as well as a command-line wallet (CLI wallet). Alphabill wallet is a hierarchical deterministic (HD) wallet, so all keys are recoverable using the main seed phrase.


Described as a series of open-source and interconnected decentralized applications powered by blockchain computing architecture.


zero-knowledge (ZK) rollup

A layer 2 scaling technique that allows blockchains to validate transactions faster while keeping fee prices low.

zero-knowledge proof (ZKP)

Proofs to verify that transactions are valid without revealing any information about these transactions, providing privacy to the transaction while maintaining its legitimacy.