The strategy of "cleanup under-aligned buffers" is not scaling well. Corner cases are still turing up. The library has some corner-case breaks, like old 32-bit Intels. And it still has not solved the AltiVec and Power8 alignment problems.
For now we are backing out the changes and investigating other strategies
Effectively this creates a workspace for encrypting the nonce. The zeroizer will run when the class is destroyed, rather than each invocation of UncheckedSetKey.
Performance went from 3.6 cpb as a temporary to 2.9 cpb as a class member
Jeffrey Walton