Theses

Dr.-Ing. Martin Novotný

Ing. Stanislav Jeřábek

Department of Digital Design

This thesis focuses on securing block ciphers against side-channel attacks that can deduce the secret key from a device's power consumption. Multiple-and dummy-rounds countermeasure was tested because its effectiveness is yet to be proven. To verify previous results and find possible errors in countermeasure design, I created VHDL implementation of PRESENT cipher secured by dummy rounds. This version underwent a series of tests that revealed a leakage at the beginning of the cryptographic operation. Further improvements led to progressively better but still unsatisfying results. The most prominent feature was the insertion of a random number of dummy clock cycles before the first valid operation. I also examined the influence of added dummy registers used as storage for outputs of dummy rounds. Furthermore, as part of my effort, I developed tools useful for future testing of multiple- and dummy-rounds countermeasure.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

The bachelor thesis deals with the inluence of prevention against fault-injection attacks on the AES cryptographic algorithm implemented on the Spartan 3E FPGA. It is investigated whether these fault detection circuits have any impact on resistance to differential power analysis attacks. In the course of the thesis, hardware implementation of AES in VHDL was developed and a program was written for DPA attack in the Matlab scripting language. Additional 5 variants were derived from the primary desing containing information redundancy for error detection during runtime. The number of patterns of consumption was found to successfully break the cipher and obtain the cipher key for each variation. The results did not reveal any greater impact on the feasibility of the attack.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

We explored the possibilities of application of Differential Power Analysis (DPA) on the implementation of AES algorithm on the FPGA Spartan-3E by Xilinx. We created two different hardware implementations of the AES cipher in VHDL language, a script implementing the DPA method in the Mathematica software and a wrapper implementing the communication between an AES module and a computer using a serial line. We inserted eight different versions of AES cipher inside the wrapper - five versions with safety measures and three basic versions without any safety measures. We compared the resistance of basic variant with the fault tolerant ones by computing the minimal number of power traces needed for breaking the correct key for each variant. We discovered that the safety measures (hardware redundacy, time redundancy and information redundancy) had minimal influence on the resistance against DPA.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

Aim of this work is to compare influence of Fault-Tolerance techniques on differential power-analysis (DPA) resistance of AES cipher implemented in Altera FPGA. After attacking simple variant, I attacked fault-tolerant variants of the cipher and compared results with the simple variant. From the comparison follows that the use of informational redundancy at SubBytes operation, spatial and time redundancy at both round and algorithm level had minimal influence on resistance against DPA, as the number of power traces necessary to obtain the key had not changed significantly.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

We explored the possibilities of the Differential Power Analysis (DPA) on the Field Programmable Gate Array (FPGA). We have modified the application for measuring a power consumption, created scripts for performing DPA, and created different implementations of AES algorithm for FPGA. Developed scripts and applications for DPA were verified against AES implementation for smart cards. Once those applications successfully broke the implementation for smart cards, we continued with the application of DPA against AES implementation for an FPGA board. DPA against FPGA was performed in six different configurations. Those configurations differed in AES implementation for FPGA, in board configuration, in oscilloscope setup, and in method of the attack. We found variants that could be successfully broken. We found out that an oscilloscope and measuring environment setups has major impact on the feasibility of the DPA on FPGA. The implementation is less important for the success of the attack. The most important aspect of the implementation was the clock frequency. We have also found out that using different power sources and removing capacitors on the FPGA board have significant impact on the feasibility of the DPA.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

The thesis explores applicability of differential power analysis (DPA) attack against FPGA implementation of AES. We created all necesery tools for DPA on FPGA, i.e. we created several variants of AES in FPGA, we developed scripts for differential power analysis and we modifed programe controling power measurements to cooperate with FPGA kit. DPA tools were verified on SmardCard implementaion of AES. Attack was succesful in these case. DPA was then applied on seven various configurations of AES implementation in FPGA.The configurations vary in VHDL code, modifed schematic of design kit and/or various power supplies. The attack was not succesful in any above configuration. In scope of this work we also propose future work in exploration of DPA applicability on field programmable gate arrays.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Jakub Klemsa

Department of Digital Design

With the rise of cloud compute services, the privacy of user's data is often put into question, as the service provider has full access to it. This is further exacerbated by facilities that hold private data, but lack the computational power to run their own research - namely hospitals. A Fully Homomorphic Encryption (FHE) could be a solution to this problem as it can evaluate arbitrary functions over encrypted data without the need for decryption on the Cloud service provider's side. Since the breakthrough by Gentry et al. in 2009, this field is very active with Chilloti et al. recently introducing the scheme called TFHE. TFHE scheme has been shown to be suitable for securing Machine Learning as a Service (MLaaS). TFHE in its original form only works with one-bit plaintext space, however, several improvements allow the usage of multivalue plaintext space. This improved version was codenamed netWork-ready TFHE (WTHE). In general, (W)TFHE Schemes implemented in software are several orders of magnitude slower than the commonly used encryption schemes. This thesis serves as a case study to determine the feasibility of accelerating the WTFHE Scheme with an FPGA. Our contributions consist of designing an FPGA accelerator capable of simple Neural Network evaluation, measuring its performance compared to the software setup, discovering resource requirements, and the potential of scalability.

Thesis on DSpace

Ing. Petr Socha

Dr.-Ing. Martin Novotný

Department of Information Security

Rainbow, a layered multivariate quadratic digital signature, is a candidate for~standardization by National institute of standards and technology (NIST). In~this paper, we present a CPA side-channel attack on the submitted 32-bit reference implementation. We evaluate the attack on an STM32F3 ARM microcontroller. After a successful attack, we propose countermeasures against side-channel attacks. Countermeasures are implemented and evaluated using leakage assessment.

Thesis on DSpace

Dr.-Ing. Martin Novotný

Ing. Vojtěch Miškovský, Ph.D.

Department of Digital Design

Every cryptographic design has to be secure to fulfil its function properly. As side-channel attacks are becoming easier and easier to perform, designers of secure circuits must pay attention to implementing various countermeasures against these attacks. However, in some cases, their hard work can be thwarted if automatic optimizations invalidate the defences. This thesis explores the effect of synthesis parameters settings on the vulnerability of the cryptographic designs implemented in FPGAs to side-channel attacks. It focuses on the implementation of AES with multiple countermeasures against attacks and evaluates the effect of parameters settings on security using Test Vector Leakage Assessment based on Welch's t-test.

Thesis on DSpace

Ing. Vojtěch Miškovský, Ph.D.

Ing. Petr Socha

Department of Digital Design

To mount a power analysis attack on a cryptographic device, one has to acquire up to millions of power traces of the attacked device. The goal of this thesis is to create a toolkit which will make the power traces acquisition faster whilst supporting as many different cryptographic schemes as possible. The toolkit will focus on hardware implentations of cryptographic schemes in FPGA.

Thesis on DSpace

Ing. Jakub Klemsa

Dr.-Ing. Martin Novotný

Department of Digital Design

Homomorphic encryption is an effective way of securing data privacy while maintaining the possibility to process the data. The VeraGreg framework, unlike other existing homomorphic cryptosystem allows for verification of computation that was done with the encrypted data. This work deals with an implementation of the VeraGreg framework and its effectiveness comparison with a na¨ive scheme based on symmetric encryption. Secure microcontroller CE1302 was chosen as the implementation platform. A new library for multiprecision integer arithmetic was created as well as the first published implementation of Paillier cryptosystem using hardware RSA accelerator. The VeraGreg framework is 200 times slower compared to the naive scheme and occupies one third more space in the program memory, so it is not a suitable alternative to symmetric cryptosystems. On the other hand, it provides privacy to the user while allowing computations with the encrypted data, and verifying that is has not been manipulated during the computation.

Thesis on DSpace

Ing. Stanislav Jeřábek

Dr.-Ing. Martin Novotný

Department of Digital Design

Field Programmable Gate Arrays (FPGAs) have an ability of dynamic reconfiguration, which allows them to be reprogrammed at runtime by itself. One computation can be implemented in different ways at different times. An actual way at a specific time is not known for an attacker and therefore it is much more difficult to use side-channel leakage to gain sensitive information. This diploma thesis follows the paper [1], which describes usage of three different countermeasures on PRESENT encryption algorithm. In this thesis, all these countermeasures were applied to PRESENT, SERPENT and AES. AES algorithm was implemented in two ways. The first way is based on the approach described in [1]. The second way uses a composite finite field to implement S-Box and therefore needs less CFGLUTs.

Thesis on DSpace

Ing. Vojtěch Miškovský, Ph.D.

Dr.-Ing. Martin Novotný

Department of Digital Design

Side-channel cryptanalysis pose a serious threat to many modern cryptographic systems. Typical side-channel attack consists of an active phase, where data are acquired, and an analytical phase, where the data get examined and evaluated. A software toolkit is presented in this thesis, which includes support for cryptographic device control, oscilloscope data acquisition, data preprocessing, statistical analysis and evaluation of the attack. The toolkit is composed of non-interactive text-based utilities with a modular plug-in architecture, and it is released under open-source licence.

Thesis on DSpace

prof. Ing. Hana Kubátová, CSc.

Dr. Paris Kitsos; Giorgio Di Natale, Ph.D.; Prof. Lejla Batina, PDEng.

Department of Digital Design

Thesis on DSpace