Non-volatile memory storing pairs of bits in such a way that both bits can be written freely, but not read directly. Only a result of some computation between bits can be read. What use might this have?

For example ( maybe this is a bad example ), usb-stick that can output only XOR result between 2 bit strings a and b. Those 2 sets of data were written in different conditions. Probably has something to do with security rather than efficiency or performance. Data a might be video and data b, written earlier, might be equally long encryption key which has a copy somewhere else too. Data a can be decrypted / un-encrypted with that copy of data b.

For this XOR example, the bits have to be read-once. Reading zeroes bits.

Or something completely different...

Just a thought.

Tried to just link this, but did not work, so here it is: