MAC and encryption keys used in financial transactions have always been stored encrypted as cryptograms (of same length) on ostensibly unassailable hardware devices using 3DES. Now the requirement is that these cryptograms be replaced with key blocks of greater length in which the key and other data is embedded. The reasoning is that they will be harder to break this way.
But since all PIN blocks must at some point in a transaction be translated from one key to another, and PIN blocks, which have a known format, would be the easiest things to decrypt, key blocks don't seem to add any security. And still, as in all symmetric systems, if one key is broken, all are.
I'm trying to understand and appreciate the need for this cumbersome new layer.