A lightweight block encryption algorithm for narrowband internet of things

With the increasingly prominent problem of data security in Narrowband Internet of Things (NB-IoT) terminal transmission, the existing cryptographic algorithms still have problems that cannot meet the security requirements of Narrowband Internet of Things terminal data and the low degree of lightweight. A lightweight block cryptographic algorithm SPNRX based on variant And-Rotate-XOR (ARX) structure and Substitute Permutation Network (SPN) structure is proposed. The proposed algorithm takes into account the unique security requirements of the NB-IoT terminal, such as simplifying the encryption process as far as possible, not too long encrypted data and high-security level, and reducing the number of encryption rounds. It overcomes the shortcoming that half of the block information of the ARX structure does not change during one round of encryption, to improve the diffusion speed. In addition, considering the security of keys and the cost of hardware implementation, a key schedule based on matrix transformation and P-box permutation is proposed. The security analysis of the SPNRX shows that the SPNRX is resistant to differential analysis, linear analysis, etc. Finally, the hardware and software performance of the SPNRX is tested. The experimental results show that the hardware implementation cost of the proposed algorithm is low; only 1357 GEs based on a 0.13 micron ASIC process are required. And the software implementation of the proposed algorithm performs well. Encryption and decryption of the proposed algorithm on the 64-bit processor take about 0.7748 ms and 0.7957 ms. And it requires 35.98 MB of memory resources. In addition, the algorithm's security strength and encryption effect are tested through key sensitivity, information entropy, etc. The results show that the proposed algorithm has high enough security.