Publications related to Keeping Authorities “Honest or Bust” with Decentralized Witness Cosigning

Secure and Efficient Cryptographic Algorithms in a Quantum World

Since the advent of internet and mass communication, two public-key cryptographic algorithms have shared the monopoly of data encryption and authentication: Diffie-Hellman and RSA. However, in the last few years, progress made in quantum physics -- and mo ...

EPFL2024

Rapidly verifiable aggregate signatures

Rachid Guerraoui, Matteo Monti, Manuel José Ribeiro Vidigueira, Martina Camaioni, Gauthier Jérôme Timothée Voron, Pierre-Louis Blaise Roman

A method for aggregating digital signatures comprises the following steps carried out by a signature aggregator: receiving first data packages from signers, each first data package comprising a signer identifier, a payload, and a payload signature; verifyi ...

2024

On the Theory and Practice of Modern Secure Messaging

Daniel Patrick Collins

Billions of people now have conversations daily over the Internet. A large portion of this communication takes place via secure messaging protocols that offer "end-to-end encryption'" guarantees and resilience to compromise like the widely-used Double Ratc ...

EPFL2024

Making Classical (Threshold) Signatures Post-quantum for Single Use on a Public Ledger

Serge Vaudenay, Laurane Chloé Angélina Marco, Abdullah Talayhan

The Bitcoin architecture heavily relies on the ECDSA signature scheme which is broken by quantum adversaries as the secret key can be computed from the public key in quantum polynomial time. To mitigate this attack, bitcoins can be paid to the hash of a pu ...

2023

Lattice-Based Blind Signatures: Short, Efficient, and Round-Optimal

Ngoc Khanh Karol Nguyen

We propose a 2-round blind signature protocol based on the random oracle heuristic and the hardness of standard lattice problems (Ring/Module-SIS/LWE and NTRU) with a signature size of 22 KB. The protocol is round-optimal and has a transcript size that can ...

Assoc Computing Machinery2023

Security in the Presence of Quantum Adversaries

Khashayar Barooti

With the looming threat of large-scale quantum computers, a fair portion of recent cryptographic research has focused on examining cryptographic primitives from the perspective of a quantum adversary. Shor's 1994 result revealed that quantum computers can ...

EPFL2023

New SIDH Countermeasures for a More Efficient Key Exchange

Andrea Basso, Tako Boris Fouotsa

The Supersingular Isogeny Diffie-Hellman (SIDH) protocol has been the main and most efficient isogeny-based encryption protocol, until a series of breakthroughs led to a polynomial-time key-recovery attack. While some countermeasures have been proposed, th ...

Springer2023

Electromagnetic Forces and Torques: From Dielectrophoresis to Optical Tweezers

Olivier Martin, Marco Riccardi

Electromagnetic forces and torques enable many key technologies, including optical tweezers or dielectrophoresis. Interestingly, both techniques rely on the same physical process: the interaction of an oscillating electric field with a particle of matter. ...

AMER CHEMICAL SOC2023

Attacks on some post-quantum cryptographic protocols: The case of the Legendre PRF and SIKE

Novak Kaluderovic

Post-quantum cryptography is a branch of cryptography which deals with cryptographic algorithms whose hardness assumptions are not based on problems known to be solvable by a quantum computer, such as the RSA problem, factoring or discrete logarithms. This ...

EPFL2022

Optimal Symmetric Ratcheting for Secure Communication

Serge Vaudenay, Andrea Felice Caforio, Daniel Patrick Collins, Hailun Yan

To mitigate state exposure threats to long-lived instant messaging sessions, ratcheting was introduced, which is used in practice in protocols like Signal. However, existing ratcheting protocols generally come with a high cost. Recently, Caforio et al. pro ...

OXFORD UNIV PRESS2022

Secret Key Generation Using Short Blocklength Polar Coding Over Wireless Channels

Yanina Yurina Shkel

This paper investigates the problem of secret key generation from correlated Gaussian random variables in the short blocklength regime. Short blocklengths are commonly employed in massively connected IoT sensor networks in 5G and beyond wireless systems. P ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Symmetry in design and decoding of polar-like codes

Kirill Ivanov

The beginning of 21st century provided us with many answers about how to reach the channel capacity. Polarization and spatial coupling are two techniques for achieving the capacity of binary memoryless symmetric channels under low-complexity decoding algor ...

EPFL2022

Single-Trace Clustering Power Analysis of the Point-Swapping Procedure in the Three Point Ladder of Cortex-M4 SIKE

Aymeric Genet, Novak Kaluderovic

In this paper, the recommended implementation of the post-quantum key exchange SIKE for Cortex-M4 is attacked through power analysis with a single trace by clustering with the k-means algorithm the power samples of all the invocations of the elliptic curve ...

Springer, Cham2022

BLOOM: Bimodal Lattice One-out-of-Many Proofs and Applications

Ngoc Khanh Karol Nguyen

We give a construction of an efficient one-out-of-many proof system, in which a prover shows that he knows the pre-image for one element in a set, based on the hardness of lattice problems. The construction employs the recent zero-knowledge framework of Ly ...

SPRINGER INTERNATIONAL PUBLISHING AG2022

A Two-Step Approach To Leverage Contextual Data: Speech Recognition In Air-Traffic Communications

Petr Motlicek, Amrutha Prasad, Juan Pablo Zuluaga Gomez

Automatic Speech Recognition (ASR), as the assistance of speech communication between pilots and air-traffic controllers, can significantly reduce the complexity of the task and increase the reliability of transmitted information. ASR application can lead ...

IEEE2022

Analysis and Improvements of the Sender Keys Protocol for Group Messaging

Daniel Patrick Collins

Messaging between two parties and in the group setting has enjoyed widespread attention both in practice, and, more recently, from the cryptographic community. One of the main challenges in the area is constructing secure (end-to- end encrypted) and effici ...

2022

Human Head Yaw Estimation based on Two 3-axis Accelerometers

Hervé Lissek, Gilles André Courtois, Vincent Pierre Olivier Grimaldi

The estimation of the orientation of an object, and a human head in particular, can be defined by the Euler angles: the yaw, pitch and roll. The robust and drift-free estimation of those angles is usually achieved with the data from several sensors such as ...

2022

Secret Key Generation Over Wireless Channels Using Short Blocklength Multilevel Source Polar Coding

Yanina Yurina Shkel

This paper investigates the problem of secret key generation from correlated Gaussian random variables in the short block-length regime. Inspired by the state-of-the-art performance provided by polar codes in the short blocklength regime for channel coding ...

IEEE2021

Full key recovery side-channel attack against ephemeral SIKE on the Cortex-M4

Aymeric Genet, Natacha Yolande Emmanuel Marie Linard de Guertechin, Novak Kaluderovic

This paper describes the first practical single-trace side-channel power analysis of SIKE. While SIKE is a post-quantum key exchange, the scheme still relies on a secret elliptic curve scalar multiplication which involves a loop of a double-and-add procedu ...

2021

Atom: A Stream Cipher with Double Key Filter

Willi Meier, Andrea Felice Caforio, Subhadeep Banik

It has been common knowledge that for a stream cipher to be secure against generic TMD tradeoff attacks, the size of its internal state in bits needs to be at least twice the size of the length of its secret key. In FSE 2015, Armknecht and Mikhalev however ...

2021