eth-xrandom

XRandom

XOR-keccak256 random number generator implementation in Javascript and Solidity. XRandom is designed to be used for smart contracts where randomness is needed.

Design

The seed of XRandom is computed as the XOR of all the inputs. The inputs are 32 bytes (a uint256 in Solidity).

The next random number is generated as the keccak-256 hash of the previous number. The generated randoms are all 32 bytes.

Implementations

Javascript

var XRandom = require('eth-xrandom')
// number, hex string, bignumber are all supported
var xrng = new XRandom([42, 1337, '0x2329'])
// the random numbers generated are `bignum` objects
var r1 = xrng.next() // get a random number anywhere between 0 and 2^256
var r2 = xrng.next('0xbeef') // get a random number with exclusive upper bound

Solidity

The contract written in Solidity is at contracts/XRandom.sol. It uses commit-reveal pattern.

• XRandom.commit
• XRandom.reveal
• XRandom.next
• XRandom.reset