cB

Carlo Brunetta

Email: brunetta@chalmers.se

Room: EDIT - 5125

About Me

Hej! I’m Carlo and I’m a Cryptography PhD student.

I ❤ Music, Nature and the Universe and I love Math ❤

I’m TAing the Cryptography, Computer Security and Network Security courses at Chalmers.

“If a man’s wit be wandering, let him study the mathematics.” - Francis Bacon

Master Thesis

Do you want to do a master thesis in Cryptography? Just contact me or drop in my office!

I’m happy to talk and see if we can collaborate!

WIP on some specific proposal

Research Interests

Block Cipher

Wiki

Block ciphers are fundamental primitives to build security and they have to be as secure as possible. The security that a BC (alone) has to achieve is directly connected on how a BC is defined in the mathematical terms. A lot of insecurity and attack that can be found are connected more on bad practices and/or computational security that it is now not more secure. The intrinsic algebraic security is based on algebraic properties that a BC has or not. They can define mathematical attacks that can broke a cipher or not: maybe the attack is the best known but it is, still, computable infeasible.

Homomoprhic Encryption

Wiki

Homomorphic encryption is a cryptographic scheme theoretically defined in 1978 by RSA’s peoples and then get (almost) practical usable by Craig Gentry in 2009.

WHAT IS HOMOMORPHIC ENCRYPTION?

HE wants to achieve the idea of algebraic homomorphism: have the possibility to do operation on encrypted data.

The idea is brilliant: you encrypt information and then can compute things without never knowing what you are working with! This permits to build scheme where the computation is done by a third entity (yeah, let’s call it the cloud) BUT homomorphic schemes are usually not that practical IRL 😢.

Blockchain

Wiki

Blockchain is a database with really peculiar rules. IMHO, there is still not a good killing-application for it.

That’s why, I’m interested in researching it!

Publications

Lattice-Based Simulatable VRFs - Challenges and Future Directions

Conf. Link
Open PDF

ProvSec 2018 - Workshop

Abstract: Lattice-based cryptography is evolving rapidly and is often employed to design cryptographic primitives that hold a great promise for being post-quantum resistant and can be employed in multiple applications such as: e-cash, unique digital signatures, non-interactive lottery and others. In such application scenarios, a user is often required to prove non-interactively the correct computation of a pseudo-random function F_k(x) without revealing the secret key k used. Commitment schemes are also useful in such application settings to commit to a chosen value, while keeping it hidden to others but being able to reveal the committed value later. In this paper, we define the first lattice-based dual-mode commitment scheme and prove that it is perfectly binding and computationally hiding. As an application, we employ our commitment scheme in order to obtain the first lattice-based non-interactive zero knowledge (NIZK) PRF argument. Furthermore, we investigate how we may construct the first lattice-based verifiable random function (VRF), and in particular a simulatable VRF (CRYPTO 2007), by employing our proposed lattice-based NIZK PRF argument.

A journal version to appear.

HIKE - Walking the Privacy Trail

DOI Link
Open PDF

CANS 2018

Abstract: We consider the problem of privacy-preserving processing of outsourced data in the context of user-customised services. Clients store their data on a server. In order to provide user-dependent services, service providers may ask the server to compute functions on the users’ data. We propose a new solution to this problem that guarantees data privacy (i.e., an honest-but-curious server cannot access plaintexts), as well as that service providers can correctly decrypt only –functions on– the data the user gave them access to (i.e., service providers learn nothing more than the result of user-selected computations). Our solution has as base point a new secure labelled homomorphic encryption scheme (LEEG). LEEG supports additional algorithms (FEET) that enhance the scheme’s functionalities with extra privacy-oriented features. Equipped with LEEG and FEET, we define HIKE: a lightweight protocol for private and secure storage, computation and disclosure of users’ data. Finally, we implement HIKE and benchmark its performances demonstrating its succinctness and efficiency.

A Differentially Private Encryption Scheme

DOI Link
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ISC 2017

Abstract: Encrypting data with a semantically secure cryptosystem guarantees that nothing is learned about the plaintext from the ciphertext. However, querying a database about individuals or requesting for summary statistics can leak information. Differential privacy (DP) offers a formal framework to bound the amount of information that an adversary can discover from a database with private data, when statistical findings of the stored data are communicated to an untrusted party. Although both encryption schemes and differential private mechanisms can provide important privacy guarantees, when employed in isolation they do not guarantee full privacy-preservation. This paper investigates how to efficiently combine DP and an encryption scheme to prevent leakage of information. More precisely, we introduce and instantiate differentially private encryption schemes that provide both DP and confidentiality.

Hidden sums and their application on block ciphers

Conf. Link
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WCC 2017

Abstract: We report the recent results on hidden sums obtained in the unpublished preprints by Brunetta, Calderini, and Sala. These hidden sums could be used to exploit some particular trapdoors in block ciphers. Each hidden sum is related to an elementary abelian regular subgroup. Focusing on the subgroups of the affine general linear group, we are able to characterize the maps generating these groups. From the characterization we obtain a polynomial-time algorithm to represent the elements of a binary vector space with respect to the hidden sum. Such an algorithm can be used to exploit the trapdoor in a block cipher. Then we design an efficient algorithm to perform the necessary preprocessing on the components of a cipher for the exploitation of the trapdoor.

This paper is the conference version of my master thesis “On some Computational Aspects for Hidden Sums in Boolean Functions” that can be found in the Trento University Library (link) or in pdf.

A complete journal version can be found in the journal Discrete Mathematics (Vol. 342)

Towards the Verification of Image Integrity in Online News

DOI Version
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ICMEW 2015

Abstract: The widespread of social networking services allows users to share and quickly spread an enormous amount of digital contents. Currently, a low level of security and trustworthiness is applied to such information, whose reliability cannot be taken for granted due to the large availability of image editing software which allow any user to easily manipulate digital contents. This has a huge impact on the deception of users, whose opinion can be seriously influenced by altered media. In this work, we face the challenge of verifying online news by analyzing the images related to the particular news article. Our goal is to create an empirical system which helps in verifying the consistency of visually and semantically similar images used within different news articles on the same topic.