Information Security Enhancement by Increasing Randomness of Stream Ciphers in GSM
Ram Prakash Prajapat, Rajesh Bhadada, Arjun Choudhary · International Journal of Advanced Computer Science and Applications · 2022
Information security is a crucial issue and needs to be addressed efficiently. Encryption of the original information is used to ensure privacy during exchange of information. In GSM (Global System for Mobile) standard, once the voice traffic initiates after signaling, encryption comes into the picture to ensure privacy during the call, after authentication. Here in this process, the plaintext is encrypted in to cipher-text using stream ciphers. For stronger security, strong ciphers with strong randomness are required. Linear Feedback Shift Registers (LFSRs) based A5 algorithm family is used for encryption in GSM. There are many shortcomings of this cipher and with these, privacy can’t be assured. Some ways are proposed in this paper to ensure better security by enhancing the randomness of the generated bit stream being used for encryption. These are incorporation of user’s current location, reuse of already generated 32 bit SRES during authentication process and conversion of linear FSRs into nonlinear FSRs. Statistical Test Suite NIST is used to test the various properties of random bit stream and an attempt has been made to achieve better randomness, hence more security.