Formal verification of cryptographic software implementations

Tese de doutoramento em InformáticaSecurity is notoriously difficult to sell as a feature in software products. In addition to meeting a set of security requirements, cryptographic software has to be cheap, fast, and use little resources. The development of cryptographic software is an area with specific needs in terms of software development processes and tools. In this thesis we explore how formal techniques, namely deductive verification techniques, can be used to increase the guarantees that cryptographic software implementations indeed work as prescribed. This thesis is organized in two parts. The first part is focused on the identification of relevant security policies that may be at play in cryptographic systems, as well as the language-based mechanisms that can be used to enforce such policies in those systems. We propose methodologies based on deductive verification to formalise and verify relevant security policies in cryptographic software. We also show the applicability of those methodologies by presenting some case studies using a deductive verification tool integrated in the Frama-c framework. In the second part we propose a deductive verification tool (CAOVerif) for a domainspecific language for cryptographic implementations (CAO). Our aim is to apply the methodologies proposed in the first part of this thesis work to verify the cryptographic implementations written in CAO. The design of CAOVerif follows the same approach used in other scenarios for general-propose languages and it is build on top of a plug-in from the Frama-c framework. At the very end, we conclude the work of this thesis by reasoning about the soundness of our verification tool.O software criptográfico possui requisitos específicos para garantir a segurança da informação que manipula. Além disso, este tipo de software necessita de ser barato, rápido e utilizar um número reduzido de recursos. Garantir a segurança da informação que é manipulada por tais sistemas é um grande desafio, sendo por isso de grande objecto de estudo actualmente. Nesta tese exploramos como as técnicas formais, nomeadamente as técnicas de verificação dedutiva, podem ser utilizadas por forma a garantir que as implementações de software criptográfico funcionam, de facto, como prescrito. O trabalho desta tese está organizado em duas partes. A primeira parte foca-se essencialmente na identificação de políticas de segurança relevantes nos sistemas criptográficos, bem como nos mecanismos baseados em linguagens que podem ser aplicados para garantir tais políticas. Neste contexto, propomos metodologias baseadas em verificação dedutiva para formalizar e verificar políticas de segurança. Mostramos também como essas metodologias podem ser aplicadas na verificação de casos de estudo reais, utilizando a ferramenta de verificação dedutiva integrada na ferramenta Frama-c. Na segunda parte, propomos uma ferramenta de verificação dedutiva (CAOVerif) para uma linguagem de domínio específico para implementações criptográficas (CAO). O desenvolvimento de tal ferramenta tem como objectivo aplicar as metodologias desenvolvidas na primeira parte deste trabalho às implementações criptográficas definidas em CAO. O desenho desta ferramenta segue a mesma aproximação de outras ferramentas de verificação dedutiva já existentes para outras linguagens. Concluímos o trabalho desenvolvido dando um prova formal da correcção da ferramenta

A deductive verification platform for cryptographic software

In this paper we describe a deductive verification platform for the CAO language. CAO is a domain-specific language for cryptography. We show that this language presents interesting challenges for formal verification, not only in the rich mathematical type system that it introduces, but also in the cryptography-oriented language constructions that it offers. We describe how we tackle these problems, and also demonstrate that, by relying on the Jessie plug-in included in the Frama-C framework, the development time of such a complex verification tool could be greatly reduced. We base our presentation on real-world examples of CAO code, extracted from the open-source code of the NaCl cryptographic library, and illustrate how various cryptography-relevant security properties can be verified.(undefined

CAOVerif : an open-source deductive verification platform for cryptographic software implementations

CAO is a domain-specific imperative language for cryptography, offering a rich mathematical type system and crypto-oriented language constructions. We describe the design and implementation of a deductive verification platform for CAO and demonstrate that the development time of such a complex verification tool could be greatly reduced by building on the Jessie plug-in included in the Frama-C framework. We discuss the interesting challenges raised by the domain-specific characteristics of CAO, and describe how we tackle these problems in our design. We base our presentation on real-world examples of CAO code, extracted from the open-source code of the NaCl cryptographic library, and illustrate how various cryptography-relevant security properties can be verified.This work was supported by Project Best Case, co-financed by the North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Bioengineered hierarchical bonelike compartmentalized microconstructs using nanogrooved microdiscs

Fabrication of vascularized large-scale constructs for regenerative medicine remains elusive since most strategies rely solely on cell self-organization or overly control cell positioning, failing to address nutrient diffusion limitations. We propose a modular and hierarchical tissue-engineering strategy to produce bonelike tissues carrying signals to promote prevascularization. In these 3D systems, disc-shaped microcarriers featuring nanogrooved topographical cues guide cell behavior by harnessing mechanotransduction mechanisms. A sequential seeding strategy of adipose-derived stromal cells and endothelial cells is implemented within compartmentalized, liquefied-core macrocapsules in a self-organizing and dynamic system. Importantly, our system autonomously promotes osteogenesis and construct's mineralization while promoting a favorable environment for prevascular-like endothelial organization. Given its modular and self-organizing nature, our strategy may be applied for the fabrication of larger constructs with a highly controlled starting point to be used for local regeneration upon implantation or as drug-screening platforms.publishe

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research