wallet-core/node_modules/randombytes/README.md

randombytes

randombytes from node that works in the browser. In node you just get crypto.randomBytes, but in the browser it uses .crypto/msCrypto.getRandomValues

var randomBytes = require('randombytes');
randomBytes(16);//get 16 random bytes
randomBytes(16, function (err, resp) {
  // resp is 16 random bytes
});