ecmh

ECMH

Implementation of the multiset hash using elliptic curves algorithm described in ecmh.wiki. Uses the secp256k1 curve and SHA256 as input.

Usage

This shows one of the usages of this library, check out the tests for more examples.

const MultiSet = require('ecmh')
const crypto = require('crypto')

function hashBytes(bytes) {
  const hash = crypto.createHash('sha256')
  hash.update(bytes)
  return hash.digest()
}

D1 = hashBytes(Buffer.from("982051FD1E4BA744BBBE680E1FEE14677BA1A3C3540BF7B1CDB606E857233E0E00000000010000000100F2052A0100000043410496B538E853519C726A2C91E61EC11600AE1390813A627C66FB8BE7947BE63C52DA7589379515D4E0A604F8141781E62294721166BF621E73A82CBF2342C858EEAC", "hex"))

D2 = hashBytes(Buffer.from("D5FDCC541E25DE1C7A5ADDEDF24858B8BB665C9F36EF744EE42C316022C90F9B00000000020000000100F2052A010000004341047211A824F55B505228E4C3D5194C1FCFAA15A456ABDF37F9B9D97A4040AFC073DEE6C89064984F03385237D92167C13E236446B417AB79A0FCAE412AE3316B77AC", "hex"))

const mset = MultiSet()
mset.addItem(D1)
console.log("d1 hash", mset.getHash('base64'))
// => d1 hash +IMZWTOmhxcMNPoa3sZv4oYYiSefsSwDo/sMporYeJM=
mset.addItem(D2)

const mset2 = MultiSet()
mset2.addItem(D2)
mset2.addItem(D1)

console.log("generates the same hash:", mset.getHash('base64'), mset2.getHash('base64'))
// => generates the same hash: +rr9ONBzcJgqNFR9r1tXuKQ5hpbW/SKUeIq9oHsfqq8= +rr9ONBzcJgqNFR9r1tXuKQ5hpbW/SKUeIq9oHsfqq8=

mset.removeItem(D2)

console.log("d1 hash same after removal", mset.getHash('base64'))
// => d1 hash same after removal +IMZWTOmhxcMNPoa3sZv4oYYiSefsSwDo/sMporYeJM=

Notes

Performance (see perf.js) is around 0.4ms per item on a modern laptop (2020), so 2500 items/s.

C++ implementation: https://reviews.bitcoinabc.org/D1072#change-bEnKePuHRgCO

Java implementation: https://github.com/softwareverde/java-cryptography/blob/master/src/main/java/com/softwareverde/cryptography/secp256k1/EcMultiset.java

bitcoin utxo fast sync: https://bitcoincashresearch.org/t/chip-2021-07-utxo-fastsync/502