Wikipedia
Xor-encrypt-xor
The xor-encrypt-xor (XEX) is a (tweakable) mode of operation of a block cipher. XEX-based tweaked-codebook mode with ciphertext stealing ( XTS mode) is one of the more popular modes of operation for whole-disk encryption.
XEX is a common form of key whitening.
XEX is part of some smart card proposals.