MODIFICATION OF THE CRYPTOGRAPHIC ALGORITHM A5/1 TO ENSURE COMMUNICATION FOR IOT DEVICES

Abstract

Internet of Things (IoT) networks exhibit high diversification due to the significant number of devices with varying characteristics, operating systems, protection algorithms, and information transmission protocols. Cryptographic algorithms, however, cannot perform equally well on different devices; most of them demonstrate low encryption speed and high memory requirements on 8-bit C0-class devices. This article explores the modification of the cryptographic algorithm A5/1 for application in IoT networks with 8-bit devices with limited computational resources. A threat model is formulated, identifying major threats and possible methods for neutralization, including cryptographic protection methods. Through the developed modification, the main drawbacks of A5/1 when applied to protect information in IoT networks have been addressed, including increasing the key length, enhancing tamper resistance, and optimizing for use on 8-bit devices. Proposed substitutions of bit data processing with byte processing have improved cryptographic qualities and made algorithm application more convenient on devices with limited computational resources. Based on statistical tests, the encrypted sequence can be considered uniformly distributed at random. For the application of the modified algorithm, a cryptographic protocol was constructed, incorporating methods for device identification and secure key management. The proposed solutions were practically implemented and tested, achieving acceptable encryption speed for many applications on an 8-bit device.