An IoT Endpoint System-on-Chip for Secure and Energy-Efficient Near-Sensor Analytics

Near-sensor data analytics is a promising direction for IoT endpoints, as it minimizes energy spent on communication and reduces network load - but it also poses security concerns, as valuable data is stored or sent over the network at various stages of the analytics pipeline. Using encryption to protect sensitive data at the boundary of the on-chip analytics engine is a way to address data security issues. To cope with the combined workload of analytics and encryption in a tight power envelope, we propose Fulmine, a System-on-Chip based on a tightly-coupled multi-core cluster augmented with specialized blocks for compute-intensive data processing and encryption functions, supporting software programmability for regular computing tasks. The Fulmine SoC, fabricated in 65nm technology, consumes less than 20mW on average at 0.8V achieving an efficiency of up to 70pJ/B in encryption, 50pJ/px in convolution, or up to 25MIPS/mW in software. As a strong argument for real-life flexible application of our platform, we show experimental results for three secure analytics use cases: secure autonomous aerial surveillance with a state-of-the-art deep CNN consuming 3.16pJ per equivalent RISC op; local CNN-based face detection with secured remote recognition in 5.74pJ/op; and seizure detection with encrypted data collection from EEG within 12.7pJ/op.Comment: 15 pages, 12 figures, accepted for publication to the IEEE Transactions on Circuits and Systems - I: Regular Paper

Residual Vulnerabilities to Power side channel attacks of lightweight ciphers cryptography competition Finalists

The protection of communications between Internet of Things (IoT) devices is of great concern because the information exchanged contains vital sensitive data. Malicious agents seek to exploit those data to extract secret information about the owners or the system. Power side channel attacks are of great concern on these devices because their power consumption unintentionally leaks information correlatable to the device\u27s secret data. Several studies have demonstrated the effectiveness of authenticated encryption with advanced data, in protecting communications with these devices. A comprehensive evaluation of the seven (out of 10) algorithm finalists of the National Institute of Standards and Technology (NIST) IoT lightweight cipher competition that do not integrate built‐in countermeasures is proposed. The study shows that, nonetheless, they still present some residual vulnerabilities to power side channel attacks (SCA). For five ciphers, an attack methodology as well as the leakage function needed to perform correlation power analysis (CPA) is proposed. The authors assert that Ascon, Sparkle, and PHOTON‐Beetle security vulnerability can generally be assessed with the security assumptions “Chosen ciphertext attack and leakage in encryption only, with nonce‐misuse resilience adversary (CCAmL1)” and “Chosen ciphertext attack and leakage in encryption only with nonce‐respecting adversary (CCAL1)”, respectively. However, the security vulnerability of GIFT‐COFB, Grain, Romulus, and TinyJambu can be evaluated more straightforwardly with publicly available leakage models and solvers. They can also be assessed simply by increasing the number of traces collected to launch the attack

On Misuse of Nonce-Misuse Resistance: Adapting Differential Fault Attacks on (few) CAESAR Winners

In this paper, we study DFA attacks on some of the CAESAR competition winners. We study the challenges imposed by the design of these modes, such as masking of the ciphertext. We also show that a very small number of nonce repetition and faults is required, which makes it very practical. We show that OCB and COLM need 1 nonce repetition and 3 faults only to uniquely identify the Key

Stacco: Differentially Analyzing Side-Channel Traces for Detecting SSL/TLS Vulnerabilities in Secure Enclaves

Intel Software Guard Extension (SGX) offers software applications enclave to protect their confidentiality and integrity from malicious operating systems. The SSL/TLS protocol, which is the de facto standard for protecting transport-layer network communications, has been broadly deployed for a secure communication channel. However, in this paper, we show that the marriage between SGX and SSL may not be smooth sailing. Particularly, we consider a category of side-channel attacks against SSL/TLS implementations in secure enclaves, which we call the control-flow inference attacks. In these attacks, the malicious operating system kernel may perform a powerful man-in-the-kernel attack to collect execution traces of the enclave programs at page, cacheline, or branch level, while positioning itself in the middle of the two communicating parties. At the center of our work is a differential analysis framework, dubbed Stacco, to dynamically analyze the SSL/TLS implementations and detect vulnerabilities that can be exploited as decryption oracles. Surprisingly, we found exploitable vulnerabilities in the latest versions of all the SSL/TLS libraries we have examined. To validate the detected vulnerabilities, we developed a man-in-the-kernel adversary to demonstrate Bleichenbacher attacks against the latest OpenSSL library running in the SGX enclave (with the help of Graphene) and completely broke the PreMasterSecret encrypted by a 4096-bit RSA public key with only 57286 queries. We also conducted CBC padding oracle attacks against the latest GnuTLS running in Graphene-SGX and an open-source SGX-implementation of mbedTLS (i.e., mbedTLS-SGX) that runs directly inside the enclave, and showed that it only needs 48388 and 25717 queries, respectively, to break one block of AES ciphertext. Empirical evaluation suggests these man-in-the-kernel attacks can be completed within 1 or 2 hours.Comment: CCS 17, October 30-November 3, 2017, Dallas, TX, US

Analysis and Design of Symmetric Cryptographic Algorithms

This doctoral thesis is dedicated to the analysis and the design of symmetric cryptographic algorithms. In the first part of the dissertation, we deal with fault-based attacks on cryptographic circuits which belong to the field of active implementation attacks and aim to retrieve secret keys stored on such chips. Our main focus lies on the cryptanalytic aspects of those attacks. In particular, we target block ciphers with a lightweight and (often) non-bijective key schedule where the derived subkeys are (almost) independent from each other. An attacker who is able to reconstruct one of the subkeys is thus not necessarily able to directly retrieve other subkeys or even the secret master key by simply reversing the key schedule. We introduce a framework based on differential fault analysis that allows to attack block ciphers with an arbitrary number of independent subkeys and which rely on a substitution-permutation network. These methods are then applied to the lightweight block ciphers LED and PRINCE and we show in both cases how to recover the secret master key requiring only a small number of fault injections. Moreover, we investigate approaches that utilize algebraic instead of differential techniques for the fault analysis and discuss advantages and drawbacks. At the end of the first part of the dissertation, we explore fault-based attacks on the block cipher Bel-T which also has a lightweight key schedule but is not based on a substitution-permutation network but instead on the so-called Lai-Massey scheme. The framework mentioned above is thus not usable against Bel-T. Nevertheless, we also present techniques for the case of Bel-T that enable full recovery of the secret key in a very efficient way using differential fault analysis. In the second part of the thesis, we focus on authenticated encryption schemes. While regular ciphers only protect privacy of processed data, authenticated encryption schemes also secure its authenticity and integrity. Many of these ciphers are additionally able to protect authenticity and integrity of so-called associated data. This type of data is transmitted unencrypted but nevertheless must be protected from being tampered with during transmission. Authenticated encryption is nowadays the standard technique to protect in-transit data. However, most of the currently deployed schemes have deficits and there are many leverage points for improvements. With NORX we introduce a novel authenticated encryption scheme supporting associated data. This algorithm was designed with high security, efficiency in both hardware and software, simplicity, and robustness against side-channel attacks in mind. Next to its specification, we present special features, security goals, implementation details, extensive performance measurements and discuss advantages over currently deployed standards. Finally, we describe our preliminary security analysis where we investigate differential and rotational properties of NORX. Noteworthy are in particular the newly developed techniques for differential cryptanalysis of NORX which exploit the power of SAT- and SMT-solvers and have the potential to be easily adaptable to other encryption schemes as well.Diese Doktorarbeit beschäftigt sich mit der Analyse und dem Entwurf von symmetrischen kryptographischen Algorithmen. Im ersten Teil der Dissertation befassen wir uns mit fehlerbasierten Angriffen auf kryptographische Schaltungen, welche dem Gebiet der aktiven Seitenkanalangriffe zugeordnet werden und auf die Rekonstruktion geheimer Schlüssel abzielen, die auf diesen Chips gespeichert sind. Unser Hauptaugenmerk liegt dabei auf den kryptoanalytischen Aspekten dieser Angriffe. Insbesondere beschäftigen wir uns dabei mit Blockchiffren, die leichtgewichtige und eine (oft) nicht-bijektive Schlüsselexpansion besitzen, bei denen die erzeugten Teilschlüssel voneinander (nahezu) unabhängig sind. Ein Angreifer, dem es gelingt einen Teilschlüssel zu rekonstruieren, ist dadurch nicht in der Lage direkt weitere Teilschlüssel oder sogar den Hauptschlüssel abzuleiten indem er einfach die Schlüsselexpansion umkehrt. Wir stellen Techniken basierend auf differenzieller Fehleranalyse vor, die es ermöglichen Blockchiffren zu analysieren, welche eine beliebige Anzahl unabhängiger Teilschlüssel einsetzen und auf Substitutions-Permutations Netzwerken basieren. Diese Methoden werden im Anschluss auf die leichtgewichtigen Blockchiffren LED und PRINCE angewandt und wir zeigen in beiden Fällen wie der komplette geheime Schlüssel mit einigen wenigen Fehlerinjektionen rekonstruiert werden kann. Darüber hinaus untersuchen wir Methoden, die algebraische statt differenzielle Techniken der Fehleranalyse einsetzen und diskutieren deren Vor- und Nachteile. Am Ende des ersten Teils der Dissertation befassen wir uns mit fehlerbasierten Angriffen auf die Blockchiffre Bel-T, welche ebenfalls eine leichtgewichtige Schlüsselexpansion besitzt jedoch nicht auf einem Substitutions-Permutations Netzwerk sondern auf dem sogenannten Lai-Massey Schema basiert. Die oben genannten Techniken können daher bei Bel-T nicht angewandt werden. Nichtsdestotrotz werden wir auch für den Fall von Bel-T Verfahren vorstellen, die in der Lage sind den vollständigen geheimen Schlüssel sehr effizient mit Hilfe von differenzieller Fehleranalyse zu rekonstruieren. Im zweiten Teil der Doktorarbeit beschäftigen wir uns mit authentifizierenden Verschlüsselungsverfahren. Während gewöhnliche Chiffren nur die Vertraulichkeit der verarbeiteten Daten sicherstellen, gewährleisten authentifizierende Verschlüsselungsverfahren auch deren Authentizität und Integrität. Viele dieser Chiffren sind darüber hinaus in der Lage auch die Authentizität und Integrität von sogenannten assoziierten Daten zu gewährleisten. Daten dieses Typs werden in nicht-verschlüsselter Form übertragen, müssen aber dennoch gegen unbefugte Veränderungen auf dem Transportweg geschützt sein. Authentifizierende Verschlüsselungsverfahren bilden heutzutage die Standardtechnologie um Daten während der Übertragung zu beschützen. Aktuell eingesetzte Verfahren weisen jedoch oftmals Defizite auf und es existieren vielfältige Ansatzpunkte für Verbesserungen. Mit NORX stellen wir ein neuartiges authentifizierendes Verschlüsselungsverfahren vor, welches assoziierte Daten unterstützt. Dieser Algorithmus wurde vor allem im Hinblick auf Einsatzgebiete mit hohen Sicherheitsanforderungen, Effizienz in Hardware und Software, Einfachheit, und Robustheit gegenüber Seitenkanalangriffen entwickelt. Neben der Spezifikation präsentieren wir besondere Eigenschaften, angestrebte Sicherheitsziele, Details zur Implementierung, umfassende Performanz-Messungen und diskutieren Vorteile gegenüber aktuellen Standards. Schließlich stellen wir Ergebnisse unserer vorläufigen Sicherheitsanalyse vor, bei der wir uns vor allem auf differenzielle Merkmale und Rotationseigenschaften von NORX konzentrieren. Erwähnenswert sind dabei vor allem die für die differenzielle Kryptoanalyse von NORX entwickelten Techniken, die auf die Effizienz von SAT- und SMT-Solvern zurückgreifen und das Potential besitzen relativ einfach auch auf andere Verschlüsselungsverfahren übertragen werden zu können