Algorand removes the technical barriers that for years undermined mainstream blockchain adoption: decentralization, scale, and security. Now you can build on a stable platform you trust.
Our consensus mechanism is Permissionless, Pure Proof of Stake. It ensures full participation, protection, and speed within a truly decentralized network. With blocks finalized in seconds, Algorand’s transaction throughput is on par with large payment and financial networks. And Algorand is the first blockchain to provide immediate transaction finality. No forking. No uncertainty.
The era of a decentralized, borderless economy is here. Algorand is the foundation. Now what will you build?
The Algorand blockchain does not fork. Unlike with proof-of-work protocols, two different blocks can never be added to the chain in the same position. Only one block can have the required threshold of signatures in order to be certified in a given round.
All transactions are final in Algorand. Once a block appears, users can rely on the transactions it contains immediately, as they can be confident that the block will forever be part of the chain. Even if the Internet is split into multiple pools of users, only one safe and consistent Algorand chain will exist.
Neither a few delegated users nor a fixed committee is responsible for proposing blocks in Algorand. Instead, all users are randomly, secretly, and continuously selected to participate in the Algorand consensus protocol. Every block in Algorand reveals a new unpredictable selection seed that determines which users participate in the next round of block selection. An online user checks whether they were selected to participate by evaluating a Verifiable Random Function (VRF) with their secret key and the selection seed. The VRF acts similar to a weighted lottery where the number of algos that the user has affects the user’s chance of being selected.
In the Algorand protocol, participants change every round of block selection in order to protect the network against attackers. Before they participate, no one knows who the users are, and once they participate, their message is already propagating through the network so it is too late for an attacker to benefit from attacking them. For each round, every set of participants is random and independent of earlier participants.
Algorand uses cryptographic sortition to select users to propose blocks for a given round. When a block is proposed to the blockchain, a committee of voters is selected to vote on the block proposal. If a super majority of the votes are from honest participants, the block can be certified.
Algorand’s Byzantine agreement protocol is highly efficient. In fact, it reaches consensus on a new block as fast as the block can be propagated throughout the network. The Algorand protocol scales to billions of users and sustains a high transaction rate—without incurring significant cost to participating users.
Algorand’s decentralized Byzantine agreement protocol can tolerate an arbitrary number of malicious users as long as honest users hold a super majority of the total stake in the system. Two important features of the consensus protocol prevent powerful adversaries from corrupting enough users so as to control block generation:
First, the adversary does not know which users he should corrupt. In fact the users who are called to certify a new block are secretly and individually selected.
Second, when the adversary realizes which users are selected, it is too late for him to benefit from attacking them. Those users has already fulfilled their responsibility in the consensus protocol. In the next round of block certification, a new set of users will again be privately and individually chosen.
The Algorand protocol is secure against an adversary who may achieve complete control over the network and dictate which users receive which messages and when. Even when the network is partitioned into multiple non-connected networks, Algorand’s blockchain does not fork and users’ balances remain secure. An adversary is never able to convince two honest users to accept two different blocks for the same round. All transactions that appear on the blockchain are always final. Algorand is able to recover after a partition is resolved and guarantees that new blocks will be generated at the same speed as before the partition.
The Algorand network has two types of nodes to simultaneously optimize decentralization and high transaction throughput.
Relay nodes allow for highly efficient communication paths.
Participation nodes propose and vote on blocks.
Any user is free to register as a relay or participation node. (Several entities---representing a wide array of technical, political, and organizational backgrounds across many different countries and continents---have already registered as relay and participation nodes.)
To ensure network security, relay nodes are both diverse and decentralized. Relay nodes are run by a number of entities representing a wide array of technical, political, and organizational backgrounds across many different countries and continents. Any network participant may host a relay node.