SPECjvm2008 crypto.rsa shows poor scalability with multiple threads. The blinding classes have many synchronized sections that cause performance blocks. WeakHashMap is not thread safe, but using it along with a concurrent queue, which allow multiple blinding objects to be used frees up the code.

When setting up the queue, overwriting is not a big issue. It may costing a few extra CPU cycles by creating two queues and an extra blinding object. But once that queue is established the queue is much faster not having a synchronize block.