The aim of the IACR Ph.D. database is twofold. On the first hand, we want to offer an overview of Ph.D. already completed
in the domain of cryptology. Where possible, this should also include a subject classification, an abstract, and
access to the full text.
On the second hand, it deals with Ph.D. subjects
currently under investigation. This way, we provide a timely
map of contemporary research in cryptology.
All entries or changes need to be approved by an editor. You can contact them via phds (at) iacr.org.
Flavio D. Garcia (#847)
Flavio D. Garcia
Topic of his/her doctorate.
Formal and Computational Cryptography: Protocols, Hashes and Commitments
Year of completion
In modern society we are surrounded by distributed systems. Most electronic devices that are currently on the market have some networking capability or are able to communicate with each other. Communication
over shared media is inherently insecure. Therefore, proper design of security protocols is of primary concern. The design and analysis of security protocols is a challenging task. Several protocols have been proposed in the
literature which later were found to be flawed. This is a consequence of the intrinsic complexity associated with the presence of a malicious adversary. The traditional complexity-theoretical adversarial model is realistic but complex. As a consequence of this, designing and analyzing protocols in
this model is error prone. The Dolev-Yao model refers to the attacker model in which an adversary has complete control over the communication media. In this model, the adversary is not bounded in running time but
is completely unable to break any cryptographic primitive. This model is satisfactory as it provides a good level of abstraction. Proofs are simpler than the complexity-theoretical ones, and therefore less error prone, still capturing most common mistakes in the design of security protocols. This thesis addresses the problem of secure protocol design from both formal and computational perspectives and also studies the relation among them. We present four original contributions:
• We present a decentralized digital currency for peer-to-peer and grid applications that is able to detect double-spending of the coins and
other types of fraud.
• We develop a formal framework for the analysis of anonymizing protocols in terms of epistemic logic. We illustrate our approach by proving sender anonymity and unlinkability of some well-known anonymizing protocols.
• We relate the Dolev-Yao model, extended with hash functions, with a realistic computational model. We use a special randomized construction to interpret hashes. We show that this model is sound and complete in presence of passive adversaries. We also show that this
model is not sound in presence of active adversaries.
• We further explore the relation between these two models considering commitment schemes and active adversaries. We propose a new stronger security notion for commitment schemes and give a novel construction that is provably secure under this definition. We illustrate the usefulness of this new machinery by giving a sound interpretation of symbolic commitments in the standard model.