A structural analysis of the A5/1 state transition graph

We describe efficient algorithms to analyze the cycle structure of the graph induced by the state transition function of the A5/1 stream cipher used in GSM mobile phones and report on the results of the implementation. The analysis is performed in five steps utilizing HPC clusters, GPGPU and external memory computation. A great reduction of this huge state transition graph of 2^64 nodes is achieved by focusing on special nodes in the first step and removing leaf nodes that can be detected with limited effort in the second step. This step does not break the overall structure of the graph and keeps at least one node on every cycle. In the third step the nodes of the reduced graph are connected by weighted edges. Since the number of nodes is still huge an efficient bitslice approach is presented that is implemented with NVIDIA's CUDA framework and executed on several GPUs concurrently. An external memory algorithm based on the STXXL library and its parallel pipelining feature further reduces the graph in the fourth step. The result is a graph containing only cycles that can be further analyzed in internal memory to count the number and size of the cycles. This full analysis which previously would take months can now be completed within a few days and allows to present structural results for the full graph for the first time. The structure of the A5/1 graph deviates notably from the theoretical results for random mappings.Comment: In Proceedings GRAPHITE 2012, arXiv:1210.611

Secure Algorithms for SAKA Protocol in the GSM Network

This paper deals with the security vulnerabilities of the cryptographic algorithms A3, A8, and A5 existing in the GSM network. We review these algorithms and propose new secure algorithms named NewA3, NewA8, and NewA5 algorithms with respect to the A3, A8, and A5 algorithms. Our NewA5 algorithm is based on block ciphers, but we also propose NewA5 algorithm with Cipher Feedback, Counter, and Output Feedback modes to convert block cipher into stream cipher. However, stream cipher algorithms are slower than the block cipher algorithm. These new algorithms are proposed to use with a secure and efficient authentication and key agreement (AKA) protocol in the GSM network. The proposed architecture is secure against partition attack, narrow pipe attack, collision attack, interleaving attack, and man-in-the-middle attack. The security analysis of the proposed algorithms are discussed with respect to the cryptanalysis, brute force analysis, and operational analysis. We choose the NewA3 and NewA8 algorithms for challenge-response and key generation, respectively. Furthermore, the NewA5 is suitable for encryption as it is efficient than the existing A5/1 and A5/2 algorithms. In case when stream cipher algorithms are required to use, our new algorithms, NewA5-CTR, NewA5-CFB, and NewA5-OFB can be used for specific applications. These algorithms are completely secure and better than the existing A5/1 and A5/2 in terms of resistant to attacks

Performance and Statistical Analysis of Stream ciphers in GSM Communications

For a stream cipher to be secure, the keystream generated by it should be uniformly random with parameter 1/2.Statistical tests check whether the given sequence follow a certain probability distribution. In this paper, we perform a detailed statistical analysis of various stream ciphers used in GSM 2G,3G, 4G and 5G communications. The sequences output by these ciphers are checked for randomness using the statistical tests defined by the NIST Test Suite. It should also be not possible to derive any information about secret key and the initial state ofthe cipher from the keystream. Therefore, additional statistical tests based on properties like Correlation between Keystreamand Key, and Correlation between Keystream and IV are also performed. Performance analysis of the ciphers also has been done and the results tabulated. Almost all the ciphers pass the tests in the NIST test suite with 99% confidence level. For A5/3stream cipher, the correlation between the keystream and key is high and correlation between the keystream and IV is low when compared to other ciphers in the A5 family

SECURITY MEASUREMENT FOR LTE/SAE NETWORK DURING SINGLE RADIO VOICE CALL CONTINUITY (SRVCC).

Voice has significant place in mobile communication networks. Though data applications have extensively gained in importance over the years but voice is still a major source of revenue for mobile operators. It is obvious that voice will remain an important application even in the era of Long Term Evolution (LTE). Basically LTE is an all-IP data-only transport technology using packet switching. Therefore, it introduces challenges to satisfy quality of service expectations for circuit-switched mobile telephony and SMS for LTE capable smartphones, while being served on the LTE network. Since 2013, mobile operators have been busy deploying Voice Over LTE (VoLTE). They are relying on a VoLTE technology called Single Radio Voice Call Continuity (SRVCC) for seamless handover between packet-switch domain to circuit-switch domain or vice versa. The aim of thesis is to review and identify the security measurement during SRVCC and verify test data for ciphering and integrity algorithm.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Securing the Internet of Things Infrastructure - Standards and Techniques

The Internet of Things (IoT) infrastructure is a conglomerate of electronic devices interconnected through the Internet, with the purpose of providing prompt and effective service to end-users. Applications running on an IoT infrastructure generally handle sensitive information such as a patient’s healthcare record, the position of a logistic vehicle, or the temperature readings obtained through wireless sensor nodes deployed in a bushland. The protection of such information from unlawful disclosure, tampering or modification, as well as the unscathed presence of IoT devices, in adversarial environments, is of prime concern. In this paper, a descriptive analysis of the security of standards and technologies for protecting the IoT communication channel from adversarial threats is provided. In addition, two paradigms for securing the IoT infrastructure, namely, common key based and paired key based, are proposed

Towards Security of GSM Voice Communication

Global system for mobile communication (GSM) is widely used digital mobile service around the world. Although GSM was designed as a secure wireless system, it is now vulnerable to different targeted attacks. There is a need to address security domains especially the confidentiality of communication. This paper presents a novel framework for end to end secure voice communication over the GSM networks using encryption algorithm AES-256. A special Modem and speech coding technique are designed to enable the transmission of encrypted speech using GSM voice channel. To the best of our knowledge, this is first solution that uses single codebook for transmission of secure voice. An efficient low bit-rate (1.9 kbps) speech coder is also designed for use with the proposed modulation scheme for optimal results. Different speech characteristics such as pitch, energy and line spectral frequencies are extracted and preserved before compression and encryption of speech. Previously, the best achieved data rate was 1.6 kbps with three codebooks, whilst the proposed approach achieves 2 kbps with 0% bit error rate. The empirical results show that the methodology can be used for real time applications to transmit encrypted voice using GSM network

International standards for stream ciphers: a progress report

The main objective of this paper is to review the current status of stream cipher standardisation. The hope is that, by doing so, the algorithms and techniques that are likely to be standardised at some point during the next year or so will be subjected to rigorous scrutiny by the crytopgraphic community