Pseudorandom
What Is Pseudorandom?
Pseudorandom describes values produced by a deterministic function that appear random and pass statistical tests of randomness, yet are fully determined by a starting value.
The word combines "pseudo" (meaning false or apparent) with "random." A pseudorandom sequence looks random to an outside observer, but it is generated by a repeatable process. If you know the exact starting point, called the seed, and the algorithm, you can reproduce the same sequence every time. True randomness, by contrast, comes from physical sources of unpredictability and cannot be reproduced.
Pseudorandomness in Blockchain
Computers cannot easily create true randomness on their own, so they use pseudorandom number generators (PRNGs). A PRNG takes a seed and applies a mathematical formula to produce a long stream of numbers that behave like random values. The same idea appears in
wallets, where a
seed phrase is used to deterministically derive the keys that control your funds.
On public blockchains, randomness is difficult because every
node must agree on the same result, and the data is transparent. If a value can be predicted or influenced, an attacker may be able to game applications such as lotteries, games, or NFT mints. To address this, many projects use a verifiable random function (VRF). A VRF produces a random-looking output together with a cryptographic proof that the output was generated correctly, so anyone can check it without being able to predict it in advance.
Chainlink VRF is a widely used example. It combines data that is unknown at the time of the request with an oracle node private key to generate both a value and a proof. A
smart contract only accepts the result after the proof is verified on-chain, which is intended to prevent tampering by node operators, users, or block builders.
Why Pseudorandomness Matters
Pseudorandomness matters because the quality of the randomness directly affects security and fairness. Weak or predictable generators can lead to actual losses. In August 2026,
a flaw in Coldcard’s PRNG led to a loss of over 1,000 BTC. A firmware error allowed attackers to generate candidate seeds, check matching Bitcoin addresses on the public blockchain, and drain wallets without ever touching the victims’ devices.
Randomness also appears in the core design of many networks. For example, some
proof-of-stake systems use pseudorandom selection to decide which validator proposes the next block, so that no single participant can always control block production.