Abstract. This paper announces a new software side-channel attackenabled by the branch prediction capability common to all modern highperformance CPUs. The penalty paid (extra clock cycles) for a mispredicted branch can be used for cryptanalysis of cryptographic primitives that employ a data-dependent program flow. Analogous to the recently described cache-based side-channel attacks our attacks also allow an unprivileged process to attack other processes running in parallel on the same processor, despite sophisticated partitioning methods such as memory protection, sandboxing or even virtualization. In this paper, we will discuss several such attacks for the example of RSA, and experimentally show their applicability to real systems, such as OpenSSL and Linux. Moreover, we will also demonstrate the strength of the branch prediction sidechannel attack by rendering the obvious countermeasure in this context (Montgomery Multiplication with dummy-reduction) as useless. Although the deeper consequences of the latter result make the task of writing an efficient and secure modular exponentiation (or scalar multiplication on an elliptic curve) a challenging task, we will eventually suggest some countermeasures to mitigate branch prediction side-channel attacks.

Abstract-Mobile communication systems are now an essential part of life throughout the world. Fourth generation "Long Term Evolution" (LTE) mobile communication networks are being deployed. The LTE suite of specifications is considered to be significantly better than its predecessors not only in terms of functionality but also with respect to security and privacy for subscribers. We carefully analyzed LTE access network protocol specifications and uncovered several vulnerabilities. Using commercial LTE mobile devices in real LTE networks, we demonstrate inexpensive, and practical attacks exploiting these vulnerabilities. Our first class of attacks consists of three different ways of making an LTE device leak its location: In our experiments, a semi-passive attacker can locate an LTE device within a 2 km 2 area in a city whereas an active attacker can precisely locate an LTE device using GPS co-ordinates or trilateration via cell-tower signal strength information. Our second class of attacks can persistently deny some or all services to a target LTE device. To the best of our knowledge, our work constitutes the first publicly reported practical attacks against LTE access network protocols.We present several countermeasures to resist our specific attacks. We also discuss possible trade-off considerations that may explain why these vulnerabilities exist. We argue that justification for these trade-offs may no longer valid. We recommend that safety margins introduced into future specifications to address such trade-offs should incorporate greater agility to accommodate subsequent changes in the trade-off equilibrium.

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Abstract. This article describes concrete results and practically validated countermeasures concerning differential fault attacks on RSA using the CRT. We investigate smartcards with an RSA coprocessor where any hardware countermeasures to defeat fault attacks have been switched off. This scenario was chosen in order to analyze the reliability of software countermeasures. We start by describing our laboratory setting for the attacks. Hereafter, we describe the experiments and results of a straightforward implementation of a well-known countermeasure. This implementation turned out to be not sufficient. With the data obtained by these experiments we developed a practical error model. This enabled us to specify enhanced software countermeasures for which we were not able to produce any successful attacks on the investigated chips. Nevertheless, we are convinced that only sophisticated hardware countermeasures (sensors, filters, etc.) in combination with software countermeasures will be able to provide security.