About Gustavo Banegas
Currently, I am a Post-Doc at the GRACE Team at INRIA in France.
From November of 2019 until November of 2020, I was a Post-Doc Researcher at the Department of Computer Science and Engineering at Chalmers University of Technology in Sweden.
In the middle of November of 2019, I finished my PhD at the Eindhoven University of Technology under the supervision of Tanja Lange and Daniel J. Bernstein. In my PhD, I was a fellow of ECRYPT-NET, an EU-financed project within the “Horizon 2020” program, thanks to one of the Marie Skłodowska-Curie actions.
In the beginning of October (2015), I defended my master thesis under the supervision of Ricardo Custódio and Daniel Panário.
In 2012, I finished my diplom in computer science at UFSC (Federal University of Santa Catarina) under the supervision of Ricardo Custódio.
PhD in Cryptography, 2019
Technische Universiteit Eindhoven
MSc in Computer Science, 2015
UFSC - Universidade Federal de Santa Catarina
BSc in Computer Science, 2012
UFSC - Universidade Federal de Santa Catarina
Side channel attacks on Post-Quantum cryptography implementations.
Side channel attacks on ECC implementations.
Software for Public Key Infrastructure.
Developed software in Java and C++
Integrated HSM in Java applications
Managed a team using Scrum
Researcher in cryptography, project manager and developer of security software, using Java, C, C++, and Python.
Tester of medical imaging software.
This paper introduces a new key space for CSIDH and a new algorithm for constant-time evaluation of the CSIDH group action. The key space is not useful with previous algorithms, and the algorithm is not useful with previous key spaces, but combining the new key space with the new algorithm produces speed records for constant-time CSIDH. For example, for CSIDH-512 with a 256-bit key space, the best previous constant-time results used 789000 multiplications and more than 200 million Skylake cycles; this paper uses 438006 multiplications and 125.53 million cycles.
This paper analyzes and optimizes quantum circuits for computing discrete logarithms on binary elliptic curves, including reversible circuits for fixed-base-point scalar multiplication and the full stack of relevant subroutines. The main optimization target is the size of the quantum computer, i.e., the number of logical qubits required, as this appears to be the main obstacle to implementing Shor’s polynomial-time discrete-logarithm algorithm. The secondary optimization target is the number of logical Toffoli gates. For an elliptic curve over a field of 2^n elements, this paper reduces the number of qubits to 7n+[log_2(n)]+9. At the same time this paper reduces the number of Toffoli gates to 48n^3+8n^(log_2(3)+1)+352n^2 log_2(n)+512n^2+O(n^(log_2(3))) with double-and-add scalar multiplication, and a logarithmic factor smaller with fixed-window scalar multiplication. The number of CNOT gates is also O(n^3). Exact gate counts are given for various sizes of elliptic curves currently used for cryptography.
Cryptographic primitives from coding theory are some of the most promising candidates for NIST’s Post-Quantum Cryptography Standardization process. In this paper, we introduce a variety of techniques to improve operations on dyadic matrices, a particular type of symmetric matrices that appear in the automorphism group of certain linear codes. Besides the independent interest, these techniques find an immediate application in practice. In fact, one of the candidates for the Key Exchange functionality, called DAGS, makes use of quasi-dyadic matrices to provide compact keys for the scheme.
The most important pre-quantum threat to AES-128 is the 1994 van Oorschot-Wiener parallel rho method, a low-communication parallel pre-quantum multi-target preimage-search algorithm. This algorithm uses a mesh of p small processors, each running for approximately $2^{128}/pt$ fast steps, to find one of $t$ independent AES keys $k_1$,…, $k_t$, given the ciphertexts AES_k_1(0), …,AES_k_t(0) for a shared plaintext $0$. NIST has claimed a high post-quantum security level for AES-128, starting from the following rationale Grover’s algorithm requires a long-running serial computation, which is difficult to implement in practice. In a realistic attack, one has to run many smaller instances of the algorithm in parallel, which makes the quantum speedup less dramatic. NIST has also stated that resistance to multi-key attacks is desirable; but, in a realistic parallel setting, a straightforward multi-key application of Grover’s algorithm costs more than targeting one key at a time. This paper introduces a different quantum algorithm for multi-target preimage search. This algorithm shows, in the same realistic parallel setting, that quantum preimage search benefits asymptotically from having multiple targets. The new algorithm requires a revision of NIST’s AES-128, AES-192, and AES-256 security claims.