The algorithm uses a key size of 128, 192, or 256 bits. It operates on blocks of 128 bits using a 16-round Feistel network structure with key whitening. Designed for speed, Xenon's round function doesn't use any S-boxes. The only operations it uses are XOR, addition, multiplication, and bit shifts.
Toshio TOKITA and Mitsuru MATSUI (1 January 2003). "Linear Cryptanalysis of Block Cipher Xenon". IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences. E86-A (1): 13–18.