I believe instead of multiplying the delta by W^t to backpropagate the error from layer l to l-1, you multiply it by a random projection B. It's hard to dig deeper because there doesn't appear to be any other information on it except here: http://isis-innovation.com/licence-details/accelerating-mach...

As an aside, are they really trying to patent a slight twist on backpropagation? That seems pretty counter-productive to me.