What is Randomised Block Selection

Randomised block selection is the mechanism by which Proof of Stake blockchain networks fairly and unpredictably designate which validator will propose the next block, preventing wealthy validators from monopolising block production while maintaining security through economic incentives.

THE NEED FOR RANDOMNESS IN BLOCK SELECTION

In Proof of Work, block selection is inherently random, and any miner who happens to find the nonce first wins the block. In Proof of Stake, if validators were selected purely by stake size, the wealthiest validator would always propose every block, creating a plutocratic, centralised system. Randomised selection ensures that while larger stakes receive proportionally more opportunities, no single validator can predict or monopolise when they will be selected.

METHODS OF RANDOMISED BLOCK SELECTION

Verifiable Random Function (VRF): Each validator uses a VRF, a cryptographic function producing a random output with a mathematical proof that the output is correct for their specific inputs (their private key, current epoch data). Validators privately compute their VRF output; those below a threshold "win" the right to propose a block. The proof allows other validators to verify the selection was legitimate without the winner being able to manipulate it. Cardano and Algorand use VRF-based leader selection.
RANDAO + VDF (Ethereum): Ethereum 2.0 uses RANDAO, a shared random beacon where validators each contribute randomness (by XORing their secret with the accumulated randomness). A Verifiable Delay Function (VDF) adds a delay preventing last-revealer manipulation. The combined output determines block proposer assignments for each epoch.
BFT-Based Random Rotation: Some chains (Cosmos, Tendermint-based) use a weighted round-robin rotation among validators with randomisation added to the ordering, each validator's turn comes proportional to their stake, but the sequence is randomised.

WHY TRULY UNBIASED RANDOMNESS IS HARD ON BLOCKCHAINS

Blockchains cannot access true randomness from external sources natively; all data must be reproducible by every node. This makes generating unpredictable-yet-verifiable randomness a deep cryptographic challenge. Chainlink VRF solves this for smart contracts by providing off-chain randomness with on-chain verification proofs.

Terms in addition to the Randomised Block Selection

Blockchain

A blockchain is a subset of a distributed database. The Bitcoin inventors originally prototyped the system in 2008. This modern database is made up of separate blocks that are connected together in a chronological chain. Blockchains may be used to store a wide range of data types. It has mostly been utilized as a public ledger for bitcoin transactions to date. A peer-to-peer network comprised of independent nodes uses a consensus process to ensure the blockchain's security and legitimacy. Each node in the network keeps a public and immutable copy of the data.

2 Factor Authentication (2FA)

2 Factor Authentication is a security measure with two layers. It is used by the majority of cryptocurrency exchanges. To log in, you must provide not only a password, but also a code obtained, for example, from the Google authenticator.

Airdrop

An airdrop is a method of distributing coins. End users can typically obtain coins for free or in exchange for doing a small task, such as subscribing to a newsletter, sending a tweet, or inviting others via a personal affiliate link. Cryptocurrency airdrops — the act of depositing cryptocurrency into public crypto wallets — are utilized as a marketing, liquidity creation, and network bootstrapping technique for many different types of blockchain initiatives.

Altcoin

Altcoin - "alternative coin" - is any kind of digital currency other than Bitcoin. Since the launch of Bitcoin, the world's first digital currency, many altcoins (as well as supporting blockchains) have been created. Altcoin digital currencies share many similarities to Bitcoin, but consistently and have significant differences. There are about 20,000 altcoins, and this number is expected to grow significantly in the coming years. Altcoins often develop Bitcoin features. Ethereum, currently the most widely used blockchain, supports digital contracts and separate applications where Bitcoin does not. Altcoins are also often created to cater to the needs of different users. The Litecoin blockchain, for example, can process payments quarterly for the duration of Bitcoin.

Cold Storage

Cold storage is the way to store cryptocurrency offline. The word refers to the use of offline wallets that are not connected to the internet. Cold storage is the most secure way to keep cryptocurrencies since an offline currency becomes less likely to be hacked and stolen. Paper wallets, printed renditions of private keys, and offline hardware and software wallets are all examples of cold storage.