cipher-ethereum/src/util.ts

An Ethereum library used by Cipher Browser, a mobile Ethereum client

import { ec as EC, KeyPair } from 'elliptic'

import BN from 'bn.js'
import createKeccakHash from 'keccak/js'

const secp256k1 = new EC('secp256k1')

export function numberToHex (
  num: number,
  includePrefix: boolean = true
): string {
  const hex = new BN(num).toString(16)
  return includePrefix ? '0x' + hex : hex
}

export function bnToHex (
  bn: BN,
  includePrefix: boolean = true
): string {
  const hex = bn.toString(16)
  return includePrefix ? '0x' + hex : hex
}

export function hexToEvenLengthHex (
  hex: string,
  includePrefix: boolean = true
): string {
  let h = (hex.match(/^0x/i) ? hex.slice(2) : hex).toLowerCase()
  if (h.length % 2 === 1) {
    h = '0' + h
  }
  return includePrefix ? '0x' + h : h
}

export function hexToBuffer (hex: string): Buffer {
  if (hex.length === 0) {
    return Buffer.alloc(0)
  }
  return Buffer.from(hexToEvenLengthHex(hex, false), 'hex')
}

export function numberToBuffer (num: number): Buffer {
  if (num === 0) {
    return Buffer.alloc(0)
  }
  return hexToBuffer(numberToHex(num, false))
}

export function bnToBuffer (bn: BN): Buffer {
  if (bn.isZero()) {
    return Buffer.alloc(0)
  }
  return hexToBuffer(bn.toString(16))
}

export function keccak256 (data: Buffer | string): Buffer {
  const buf = data instanceof Buffer ? data : Buffer.from(data, 'utf8')
  return createKeccakHash('keccak256').update(buf).digest()
}

export function decompressPublicKey (publicKey: Buffer): Buffer {
  const length = publicKey.length
  const firstByte = publicKey[0]
  if ((length !== 33 && length !== 65) || firstByte < 2 || firstByte > 4) {
    throw new Error('invalid public key')
  }
  let key: KeyPair
  try {
    key = secp256k1.keyFromPublic(publicKey)
  } catch (_err) {
    throw new Error('invalid public key')
  }
  return Buffer.from(key.getPublic().encode())
}