code: function round() {
        i++
        var shasum = Crypto.createHash('sha512')
        shasum.update(out, 'utf8')
        out = shasum.digest('hex')
        if (rounds <= i) {
          return done(out)
        }
        if (0 === i % 88) {
          return process.nextTick(round)
        }
        round()
      }
docs: don't chew up the CPU