Aptos Whitepaper in 5 Minutes

Introduction

The world of blockchain and cryptocurrencies has been rapidly expanding through the years.

However, many blockchains today face several limitations. These limitations include ↓

Lack of Scalability

Most blockchains can only handle a limited number of transactions per second.

High fees

High usage can lead to network congestion, resulting in slower transaction times and higher fees per transaction.

Centralization

Some blockchains are centralized. In centralized systems, all data and operations are managed by a single entity or a small group of entities.This creates a single point of failure, making the system more vulnerable to attacks. Centralized systems also often operate with less transparency.

Security Vulnerabilities

Proof-of-Work consensus mechanisms are vulnerable to 51% attacks, in which a single entity or group of entities attempts to control more than 50% of the network’s mining or validation power, taking over the network if successful.

Aptos seeks to overcome these limitations with a decentralized, secure, and scalable network managed by its user community, capable of expanding its computational resources to meet growing global demands.

VISION

“To deliver a blockchain that can bring mainstream adoption to [W]eb3 and empower an ecosystem of decentralized applications to solve real-world user problems.”

MISSION

To advance the state-of-the-art in blockchain reliability, safety, and performance by providing a flexible and modular blockchain architecture. This architecture should support frequent upgrades, fast adoption of the latest technology advancements, and first-class support for new and emerging use cases.

Aptos envisions blockchains becoming as common as cloud infrastructure.

what is aptos?

Launched in 2022, Aptos is a secure and scalable blockchain network.

Aptos Labs, a supporting entity of the network, states that Aptos leverages technology developed for Meta’s Diem blockchain, including the Move programming language. The mainnet launched on Oct. 12, 2022.

CORE DESIGN PRINCIPLES

Low Fees

Aptos keeps fees low by optimizing transaction processing, aligning fees with real-world costs, and giving developers flexibility in managing their application's expenses.

Upgradeability

Aptos’ modular design allows for flexibility and adaptability for frequent upgrades. It supports emerging use cases seamlessly.

Scalability

Aptos maximizes throughput through parallelizing and batch processing of transactions. Parallelizing transactions means that multiple transactions are processed simultaneously rather than sequentially. Parallelizing transactions makes the blockchain more efficient and capable of handling a larger volume of transactions in a timely manner.

Security and User Experience

The Aptos data model allows for flexible key management and hybrid custodial options. It also ensures transaction transparency before signing and supports practical light client protocols, making the user experience safer and more trustworthy.

The Aptos blockchain aims to be fast and efficient for all users.

To understand how Aptos achieves such principles, it's essential to examine the key technological innovations it employs, starting with the Move programming language.

Move Programming Language

Inspired by the Rust programming language, Move is a new smart contract programming language used by the Aptos blockchain, designed for safety and flexibility.

It utilizes an object model to represent the ledger state and employs Move code (modules) to define rules for state transitions. Users can submit transactions to publish or upgrade modules, execute functions within modules, or run scripts that interact with module interfaces.

It supports module upgrades and comprehensive programmability, allowing configuration changes and blockchain upgrades without downtime. Move ensures that resources cannot be produced without credentials, double spent, or disappear.

Now let’s explore how transactions take place on Aptos!

Transaction Processing Lifecycle

a. Dissemination

Dissemination involves broadcasting transactions to the network, ensuring that all nodes are aware of new transactions. It is the initial stage where incoming transactions are received and prepared for processing. Dissemination ensures that a continuous stream of transactions is available for processing, contributing to the overall throughput of the system.

B. Block Metadata Ordering

Block metadata ordering is the process by which validators agree on the order of transactions within a block. This step is crucial for maintaining the integrity and consistency of the blockchain. This is the stage where transactions are organized and prioritized for inclusion in a block.

c. Parallel Execution

The Block-STM execution engine allows for parallel transaction processing which maximizes throughput by dividing transaction processing into independent, parallel stages. Parallel execution is the culmination of the transaction lifecycle, where transactions are processed concurrently, in other stages, to achieve optimal performance.

D. Batch Storage

Batch storage involves permanently storing verified transactions on the blockchain. This is the final stage where processed transactions are stored in the blockchain.

E. Ledger Certification

Ledger certification involves providing light client verification using proofs from validators/full nodes. While not directly related to transaction processing, ledger certification ensures the integrity and trustworthiness of the blockchain by provides assurance to light clients that the blockchain state is valid and consistent, enabling them to interact with the blockchain securely. By providing reliable verification mechanisms, ledger certification enhances the overall reliability and usability of the blockchain system.

Note

All stages are completely independent from each other. Transactions are processed in batches.
Batch processing in the Aptos blockchain is a key efficiency optimization present in every stage of transaction processing.
Validators group transactions into batches during dissemination, which are then combined into blocks during consensus.
This batching extends to execution, storage, and ledger certification phases, offering benefits like reordering, reducing operations, and enabling parallel execution.

State Synchronization Protocol

A critical aspect of any blockchain network is ensuring all participants have a consistent view of the latest state of the blockchain

The Aptos State Synchronization Protocol achieves this by efficiently distributing and verifying blockchain data for different types of users within the network.

Leader reputation mechanism promotes honest validators and minimizes impact of failures. In addition, Authenticated Ledger History and Certified State Proofs are used to offer a flexible synchronization protocol. These proofs are provided by validators, full nodes, and other replicators.

Consensus and Governance

Several key players are responsible for validating transactions and ensuring network security within Aptos.

PARTICIPANTS

VALIDATORS

Validators contribute essential data like round numbers, IDs, hash values, and digital signatures for consensus.
AptosBFT operates on a round-by-round basis with a designated leader for each cycle.
Responsible for transaction processing and securing the network

CLIENTS

Clients within the system refer to any entity that requires either submitting transactions or accessing the state and history of the blockchain.
These clients have the option to retrieve and authenticate proofs of data from validators.

2 TYPES OF CLIENTS

Full Nodes

Capabilities

Store and maintain the entire blockchain history and state.
Verify and process all transactions from the beginning of the blockchain.
They may choose to trim transaction history and blockchain state to save storage space.

Resource Requirements

Require significant storage capacity and computational power.
Higher bandwidth needs due to processing and storing large amounts of data.

Role in Network

Provide comprehensive validation and verification of blockchain data.
Serve as a source of complete blockchain data for other nodes in the network.
Can participate in consensus.

LIght CLIENTS

Capabilities

Track and store a small part of the blockchain state, usually from full nodes.
Do not store the full transaction history, only the essential data required for specific operations.
Synchronize partial blockchain states, such as specific accounts or data values.
Enable verified state reads, such as fetching verified account balances without downloading the entire blockchain.

Resource Requirements

Require significantly less storage and computational power compared to full nodes.
Lower bandwidth needs due to processing and storing smaller amounts of data.

Role in Network

Provide efficient access to blockchain data with minimal resource usage.
Depend on full nodes or other trusted sources for data verification and completeness.
Commonly used by wallets and lightweight applications.

CONSENSUS MECHANISM

Validators collectively maintain the integrity of the blockchain through a Byzantine fault-tolerant (BFT) consensus mechanism called AptosBFT.
This ensures the security and reliability of the blockchain network, even in the presence of malicious actors or faulty nodes. It offers strong fault tolerance, enabling the network to withstand up to one-third of validators being faulty while maintaining network integrity.
Validators failing to meet the protocol's criteria may face penalties or restrictions on their participation.

Token holders participate in the consensus process by locking up, or staking, their tokens with chosen validators.
The amount staked by each token holder determines the weight of their voting power within the consensus mechanism.
Validators with higher stakes wield more influence in the decision-making process of the blockchain network.

Thus, AptosBFT is a combination of both Byzantine Fault Tolerance (BFT) and Proof-of-Stake (PoS) systems.
AptosBFT contributes to achieving a throughput of 160,000 transactions per second with latency reduced to under one second.
The Aptos coin (APT) is utilized for transaction fees, staking, and governance.

Homogeneous State Sharding

The Aptos blockchain is designed to power the next generation of decentralized applications.

While its current architecture offers significant advantages in terms of scalability. upgradability, security, and user experience, the Aptos team is constantly innovating to ensure the network remains adaptable and future-proof.

While initially starting with a single ledger state, they plan to implement homogeneous state sharding in the near future

This approach will divide the blockchain into multiple shards, each with its own ledger state but a common API, allowing for horizontal scalability while maintaining decentralization as the network can handle more transactions by distributing the load across multiple shards.

Different shards can be optimized for various system characteristics, providing flexibility and efficiency for different applications.

Glossary

Transaction Throughput: The number of transactions a system can process in a given period of time.

Network Congestion: A situation where a network's capacity is exceeded by the volume of transactions, leading to slower processing times and higher fees.

Proof-of-Work (PoW): A consensus mechanism that requires participants to perform computational work to propose new blocks to the blockchain, ensuring security through resource expenditure.

Diem: A blockchain-based payment system that was developed by Meta (formerly Facebook).

Mainnet: The primary network where actual transactions occur on a blockchain, as opposed to test networks.

Consensus Mechanism: A process used in blockchain systems to ensure all participants agree on the current state of the blockchain.

Sharding: A method used to split a database into smaller, more manageable pieces called shards, each with its own data but part of a unified system.

API (Application Programming Interface): A set of rules that allows different software entities to communicate with each other.

Byzantine Fault Tolerance (BFT): A property of a system that can resist certain types of failures or attacks and continue to operate correctly.

Proof-of-Stake (PoS): A consensus mechanism that allows participants to propose new blocks to the blockchain based on the number of tokens they hold and are willing to 'stake' as collateral.

Token Holder: An individual or entity that owns a certain amount of cryptocurrency tokens.

Staking: The act of locking up cryptocurrency tokens to support the operations of a blockchain network in exchange for rewards.

Horizontal Scalability: The ability to boost capacity by adding more units (hardware or software) to work together as one system.

Contact Aptos

Full Whitepaper