What Is Random Beacon?
Also known as: Randomness Beacon, Verifiable Randomness Source
In short
A random beacon is a system that publishes random values at regular intervals that anyone can verify, that cannot be predicted in advance, and that cannot be manipulated by a single party. Blockchains use it for tasks such as validator selection.
Blockchains are deterministic systems; the same inputs must produce the same result on every node. For this reason, generating trustworthy randomness inside the chain is hard: a number derived from block data can be influenced by the party producing the block. Random beacons try to solve this problem by generating randomness with the contributions of multiple participants and with cryptographic proofs.
There are different implementations. Ethereum's Proof of Stake system uses a mechanism called RANDAO: each block proposer adds its own contribution, and these contributions are combined to select the validators who will propose blocks and vote in later epochs. Networks such as drand use threshold signatures to publish random values that cannot be produced until a certain majority of participants come together and that anyone can verify. Some networks, such as the Internet Computer, also use a similar threshold-signature beacon.
The limits vary by design. In RANDAO, the participant who gives the last contribution can influence the result to a limited extent by choosing not to publish their block. In threshold-signature-based systems, secret collusion by a sufficient share of participants breaks security. For this reason, high-value applications carefully evaluate the source of randomness and its trust assumptions.
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