In scala there is a java implementation of ThreadLocalRandom ( https://github.com/scala/scala/blob/0b47dc2f28c997aed86d6f615da00f48913dd46c/src/forkjoin/scala/concurrent/forkjoin/ThreadLocalRandom.java ) if this implementation of Random (that basically uses Date.now()) satisfy you ( https://github.com/gwtproject/gwt/blob/master/user/super/com/google/gwt/emul/java/util/Random.java ))
I will go for an implementation in pure Scala.