NIS05-5: Energy Efficient Wireless Encryption

The current encryption standard for wireless networks recommend using the AES cipher in the counter (CTR) mode for confidentiality and in the cipher block chaining (CBC) mode for authentication. In the counter mode, a 128 bit counter is encrypted using the AES into 128 bit keystream which is then XORed with 128 bits of plaintext before transmission. This operation is repeated for the entire frame and results in heavy energy consumption for larger frames. In this paper, we propose a novel cipher called High Diffusion (HD) cipher that securely expands a given 128 bit counter value to a larger 288 bit keystream during encryption, thus reducing the number of encryptions per frame compared to the AES. We show that the HD cipher is as secure as the AES under differential, linear cryptanalysis and the Square attack. Using an experimental set up consisting of a laptop with 1.8 GHz Pentium 4 processor and an Intrinsyc CerfCube with 233 MHz ARM processor we measure the energy consumption of both the AES and the HD cipher encryption operation. We observe that using HD cipher instead of AES for encryption will result in about 40% saving in energy consumption on both the laptop and the CerfCube. We also observe that energy efficiency due to HD cipher is significant for larger frame lengths.