Calls to `crypto.randomFillSync` was added in Node.js v6.13.0, so we have to add a polyfill if users use Node.js 6.12.3 or below.
Calls to
crypto.randomFillSyncwas added in Node.js v6.13.0, so we have to add a polyfill if users use Node.js 6.12.3 or below.