Retoring original mnemonic from part 1 and part 2 using @iov/crypto

mnemonic_restore.js

const part1 = 'pencil accuse tennis element peanut tent venue message process stove glory gym'
const part2 = 'panic roof boil axis mom enjoy change margin stove heavy forum food'

const part1Entropy = Bip39.decode(new EnglishMnemonic(part1))
const part2Entropy = Bip39.decode(new EnglishMnemonic(part2))

const restoredEntropy = part1Entropy.map((byte, index) => byte ^ part2Entropy[index]) 
const restored = Bip39.encode(restoredEntropy).toString()
// 'dial ring shiver firm connect nominee stairs army large rubber deal crater'