// loaded by LOAD_KEY, and key size information held in CR1EQ/CR2EQ.
//
// Vxor is ideally V6 (Key[0-3]), but for slightly improved encrypting
// performance V6 and IVEC can be swapped (xor is both associative and
// commutative) during encryption:
//
//	VXOR INOUT, IVEC, INOUT
//	VXOR INOUT, V6, INOUT
//
//	into
//
//	VXOR INOUT, V6, INOUT
//	VXOR INOUT, IVEC, INOUT
//