NATO Science for Peace and Security Series - D: Information and Communication Security (IOS Press) – serie

The real power for security applications will come from the synergy of academic and commercial research focusing on the specific issue of security. Special constraints apply to this domain, which are not always taken into consideration by academic research, but are critical for successful security applications: large volumes: techniques must be able to handle huge amounts of data and perform ‘on-line’ computation; scalability: algorithms must have processing times that scale well with ever growing volumes; automation: the analysis process must be automated so that information extraction can ‘run on its own’; ease of use: everyday citizens should be able to extract and assess the necessary information; and robustness: systems must be able to cope with data of poor quality (missing or erroneous data). The NATO Advanced Study Institute (ASI) on Mining Massive Data Sets for Security, held in Italy, September 2007, brought together around ninety participants to discuss these issues. This publication includes the most important contributions, but can of course not entirely reflect the lively interactions which allowed the participants to exchange their views and share their experience. The bridge between academic methods and industrial constraints is systematically discussed throughout. This volume will thus serve as a reference book for anyone interested in understanding the techniques for handling very large data sets and how to apply them in conjunction for solving security issues.

Recent decades have seen major advances in methods and tools for checking the safety and security of software systems. Automatic tools can now detect security flaws not only in programs of the order of a million lines of code, but also in high-level protocol descriptions. There has also been something of a breakthrough in the area of operating system verification. This book presents the lectures from the NATO Advanced Study Institute on Tools for Analysis and Verification of Software Safety and Security; a summer school held at Bayrischzell, Germany, in 2011. This Advanced Study Institute was divided into three integrated modules: Foundations of Safety and Security, Applications of Safety Analysis and Security Analysis. Subjects covered include mechanized game-based proofs of security protocols, formal security proofs, model checking, using and building an automatic program verifier and a hands-on introduction to interactive proofs.Bringing together many leading international experts in the field, this NATO Advanced Study Institute once more proved invaluable in facilitating the connections which will influence the quality of future research and the potential to transfer research into practice. This book will be of interest to all those whose work depends on the safety and security of software systems.

Cyberspace is a ubiquitous realm interconnecting every aspect of modern society, enabled by broadband networks and wireless signals around us, existing within local area networks in our schools, hospitals and businesses, and within the massive grids that power most countries. Securing cyberspace to ensure the continuation of growing economies and to protect a nation’s way of life is a major concern for governments around the globe. This book contains papers presented at the NATO Advanced Research Workshop (ARW) entitled Best Practices and Innovative Approaches to Develop Cyber Security and Resiliency Policy Framework, held in Ohrid, the Former Yugoslav Republic of Macedonia (FYROM), in June 2013. The workshop aimed to develop a governing policy framework for nation states to enhance the cyber security of critical infrastructure. The 12 papers included herein cover a wide range of topics from web security and end-user training, to effective implementation of national cyber security policies and defensive countermeasures. The book will be of interest to cyber security professionals, practitioners, policy-makers, and to all those for whom cyber security is a critical and an important aspect of their work.

This book had its origins in the NATO Advanced Study Institute (ASI) held in Ohrid, Macedonia, in 2014. The focus of this ASI was the arithmetic of superelliptic curves and their application in different scientific areas, including whether all the applications of hyperelliptic curves, such as cryptography, mathematical physics, quantum computation and diophantine geometry, can be carried over to the superelliptic curves.Additional papers have been added which provide some background for readers who were not at the conference, with the intention of making the book logically more complete and easier to read, but familiarity with the basic facts of algebraic geometry, commutative algebra and number theory are assumed.The book is divided into three sections. The first part deals with superelliptic curves with regard to complex numbers, the automorphisms group and the corresponding Hurwitz loci. The second part of the book focuses on the arithmetic of the subject, while the third addresses some of the applications of superelliptic curves.

ICT plays a crucial role in the pursuit of modernization in the countries of Slovenia, Croatia, Albania and Bulgaria, which form the South Eastern European (SEE) region., The quest for Euro-Atlantic integration and the undeniable necessity for direct foreign investment have encouraged the SEE countries to invest in the development of cyber technology, and it has become the dominant area for social, economic and political interaction within the region. This has had both positive and negative consequences.This book presents the proceedings of the NATO Advanced Training Course (ATC), held in Ohrid, former Yugoslav Republic of Macedonia, in December 2014. The ATC addressed serious concerns about terrorist use of cyber technology in South Eastern Europe, which not only has the potential to destabilize regional efforts to create a platform for increased development by creating a breeding ground for the training of extremists and the launching of cyber attacks, but also represents a direct and indirect threat to the security and stability of other NATO partner countries.The book will be of interest to all those involved in countering the threat posed by terrorist use of the Internet worldwide.

Critical energy infrastructure such as oil and gas pipelines, storage facilities and electricity grids are increasingly becoming the target of criminal and terrorist attacks.This book contains the papers presented at the NATO Advanced Research Workshop (ARW) ‘The Protection of Critical Energy Infrastructure against Emerging Security Challenges’, held in Tbilisi, Georgia, in November 2014.The main objective of this ARW was to investigate the security risks to critical energy infrastructure, namely cyber and terrorist attacks, as well as to identify opportunities for public-private partnerships to meet these risks. The workshop served as a forum for experts and stakeholders from government, academia and the private sector to exchange information and best practice and to produce findings and recommendations for integrated security solutions involving close cooperation between public and private stakeholders.Underlining the importance of a holistic approach to European energy security, this book will be of interest to all those involved in protecting critical energy infrastructure from a diverse range of threats.

Hybrid conflicts are characterized by multi-layered efforts to undermine the functioning of the State or polarize society.This book presents results, recommendations and best practices from the NATO Advanced Research Workshop (ARW) ""Critical Infrastructure Protection Against Hybrid Warfare Security Related Challenges"", held in Stockholm, Sweden, in May 2016. The main objective of this workshop was to help and support NATO in the field of hybrid conflicts by developing a set of tools to deter and defend against adversaries mounting a hybrid offensive. Addressing the current state of critical infrastructure protection (CIP) and the challenges evolving in the region due to non-traditional threats which often transcend national borders – such as cyber attacks, terrorism, and attacks on energy supply – the widely ranging group of international experts who convened for this workshop provided solutions from a number of perspectives to counter the new and emerging challenges affecting the security of modern infrastructure. Opportunities for public-private partnerships in NATO member and partner countries were also identified.The book provides a highly topical resource which identifies common solutions for combating major hazards and challenges – namely cyber attacks, terrorist attacks on energy supply, man-made disasters, information warfare and maritime security risks – and will be of interest to all those striving to maintain stability and avoid adverse effects on the safety and well-being of society.

The sheer quantity of widely diverse data which now results from multiple sources presents a problem for decision-makers and analysts, who are finding it impossible to cope with the ever-increasing flow of material. This has potentially serious consequences for the quality of decisions and operational processes in areas such as counterterrorism and security.This book presents the papers delivered at the NATO Advanced Research Workshop (ARW) 'Meeting Security Challenges through Data Analytics and Decision Support’, held in Aghveran, Armenia, in June 2015. The aim of the conference was to promote and enhance cooperation and dialogue between NATO and Partner countries on the subject of effective decision support for security applications. The attendance of many leading scientists from a variety of backgrounds and disciplines provided the opportunity to improve mutual understanding, as well as cognizance of the specific requirements and issues of Cyber Physical Social Systems (CPPS) and the technical advances pertinent to all collaborative human-centric information support systems in a variety of applications. The book is divided into 3 sections: counter terrorism: methodology and applications; maritime and border security; and cyber security, and will be of interest to all those involved in decision-making processes based on the analysis of big data.

With the increased dependence on digital and internet technologies, cyber security has come to be regarded as a national security issue, and the number of countries with a published cyber security strategy continues to rise. But these national cyber security strategies often run the risk of failing to address all the cyber security requirements of the many institutions within a given country, and the complex nature of the stakeholders involved and the networks formed by them means that the problem requires an interdisciplinary approach. This book presents papers from the NATO Advanced Research Workshop (ARW) entitled “A Framework for a Military Cyber Defense Strategy”, held in Norfolk, Virginia, USA, in April 2016. The workshop focused on key priority areas for cyber defense along with NATO’s cyber defense policy implementation and brought together experts with an eclectic mix of backgrounds and specialties from a group of NATO member states and partner countries. The participants considered not only the technical implications of cyber security efforts, but also the legal, strategic, educational and organizational aspects, and the book reflects this wide view of the field and its intricacies, highlighting the complexity of cyber security and the many challenges it presents. This overview of cyber security offers state-of-the-art approaches from a multidisciplinary standpoint, and will be of interest to all those working in the field.

Recent decades have seen an increase in the number of terrorist attacks, necessitating the development of more efficient global security policies. One of the most important elements of this enhanced security is the protection of critical infrastructure. This book presents edited contributions from the NATO Advanced Training Course (ATC) on Critical Infrastructure Protection - Best Practices and Innovative Methods of Protection, held in Agadir, Morocco, from 6 to 12 May 2018. The main objective of the course was to bring together specialists working in the area of protecting critical infrastructure in NATO Member and Partner countries to share their knowledge and expertise. One lecture block was dedicated to important legal aspects, as these differ from country to country. The other main topic areas included the structural design and protection of critical infrastructure, new materials and material analysis, and material and construction testing at elevated impact velocities via experiment and numerical simulation. New designs for critical infrastructure elements were also demonstrated.The course provided an ideal forum for speakers and participants from government, academia, and military bodies to exchange information and best practice, while at the same time creating links to foster further collaboration and the exchange of ideas about the protection of critical infrastructure, and the book will be of interest to all those whose work involves protecting critical infrastructure from the threat of terrorist attack.

Almost all technical systems currently either interface with or are themselves largely software systems. Software systems must not harm their environment, but are also often vulnerable to security attacks with potentially serious economic, political, and physical consequences, so a better understanding of security and safety and improving the quality of complex software systems are crucial challenges for the functioning of society. This book presents lectures from the 2018 Marktoberdorf summer school Engineering Secure and Dependable Software Systems, an Advanced Study Institute of the NATO Science for Peace and Security Programme. The lectures give an overview of the state of the art in the construction and analysis of safe and secure systems. Starting from the logical and semantic foundations that enable reasoning about classical software systems, they extend to the development and verification of cyber-physical systems, which combine computational and physical components and have become pervasive in aerospace, automotive, industry automation, and consumer appliances. Safety and security have traditionally been considered separate topics, but several lectures in this summer school emphasize their commonalities and present analysis and construction techniques that apply to both.The book will be of interest to all those working in the field of software systems, and cyber-physical systems in particular.

Emerging alongside the widespread adoption of networked information technologies, cybersecurity incidents represent a significant threat to our common well-being. The institutional construct of a Computer-Emergency Response Team (CERT) began to evolve thirty years ago as a response to security incidents in the nascent Internet.This book, Next Generation CERTs, presents papers arising from the NATO Advanced Research Workshop “New Generation CERT: from Response to Readiness - Strategy and Guidelines”, held in Chiavari, Italy, from 28 - 30 March 2017. The workshop enabled 38 leading experts from NATO members and affiliate states to discuss the limitations of current CERTs and identify the improvements that are likely to shape the CERTs of the future. After the workshop, participants were invited to submit the papers included here.The book is divided into 3 main sections: state of the art; next generation CERTs; and the experience of CERTs. A number of approaches are covered – technical, tactical, strategic – which could be applied to both civilian and military environments. Providing an insight into the likely future development of CERTs, the book will be of interest to all those involved in the field of cybersecurity.

Hybrid threats represent one of the rising challenges to the safe and effective management of digital systems worldwide. The deliberate misuse or disruption of digital technologies has wide-ranging implications for fields as diverse as medicine, social media, and homeland security. Despite growing concern about cyber threats within many government agencies and international organizations, few strategies for the effective avoidance and management of threats or the prevention of the disruption they can cause have so far emerged. This book presents multiple perspectives based upon a NATO Science for Peace and Security Programme Advanced Research Workshop on ‘Resilience and Hybrid Threats’ held in Pärnu, Estonia from 26-29 August 2018, and includes a mixture of workshop summary papers and invited perspectives from world experts. Topics include the development of strategies for the protection and recovery of systems affected by hybrid threats, and the benefits of those strategies under different disruption scenarios. The role of risk and resilience assessment pertaining to the information domain is a common focus across all perspectives.Offering an overview of resilience-based decision making through an approach that integrates the threats and dependencies related to infrastructural, informational, and social considerations, the book will be of interest to all those whose work involves the security of digital systems.

Water supply and water management services are among the most critical infrastructures in society, providing safe and affordable drinking water, managing wastewater to avoid floods and environmental pollution, and enabling the reuse and replenishment of scarce water resources. With water and wastewater facilities and infrastructure intrinsic to our towns and cities, we must not underestimate the potentially catastrophic results of water supply contamination or disruption to the systems that regulate the water we rely on for essential agricultural, environmental, and municipal needs.This book presents 12 papers selected from those delivered at the NATO Advanced Research Workshop (ARW) on Physical and Cyber Safety in Critical Water Infrastructure, held in Oslo, Norway, from 8-11 October 2018. The conference brought together resource persons and decision makers from 12 NATO countries and 6 partner countries to share their experiences with the objective of formulating best practice based on recommendations and conclusions, to increase awareness of the risks that threaten current and future water utilities and services, to learn how to improve surveillance and preparedness, and to deal with a crisis should all else fail. Addressing the urgent need to focus on physical and cyber safety in one of the most critical infrastructures in our society, the book will be of interest to all those working in the field of water supply and waste water management.

Space-critical infrastructures represent an interdependent system of systems consisting of workforce, environment, facilities, and multidirectional interactions. These are essential for the maintenance of vital societal functions such as health, safety, security, mobility, and the economic and social well-being of people, and their destruction or disruption would have a significant impact on society as a whole. In all, 79 nations and government consortia currently operate satellites, with 11 countries operating 22 launch sites. Despite creating new challenges, this multi-actor environment offers opportunities for international cooperation, but making the most of these opportunities requires a holistic approach to space-critical infrastructure, away from strictly defined space technologies and towards understanding the resilience of complex systems and how they are intertwined in reality.This book presents papers from the NATO Advanced Research Workshop (ARW), entitled Critical Space Infrastructure: From Vulnerabilities and Threats to Resilience, held in Norfolk, Virginia, USA from 21-22 May 2019. The ARW brought together representatives from academia, industry, and international organizations in an effort to deepen scientific and technological understanding of space-critical infrastructures and explore the implications for national and international space security and resilience. It examined space as a critical infrastructure from a multidisciplinary perspective in accordance with NATO’s Strategic Concept.The 29 chapters in the book are divided into six sections covering space infrastructure: governance; cybersecurity; risk, resiliency and complexity; emerging technologies such as block chain, artificial intelligence and quantum computing; application domains; and national approaches and applications.

Until recently, the Arctic was almost impossible for anyone other than indigenous peoples and explorers to traverse. Pervasive Arctic sea ice and harsh climatological conditions meant that the region was deemed incapable of supporting industrial activity or a Western lifestyle. In the last decade, however, that longstanding reality has been dramatically and permanently altered. Receding sea ice, coupled with growing geopolitical disputes over Arctic resources, territory, and transportation channels, has stimulated efforts to exploit newly-open waterways, to identify and extract desirable resources, and to leverage industrial, commercial, and transportation opportunities emerging throughout the region.This book presents papers from the NATO Advanced Research Workshop (ARW) Governance for Cyber Security and Resilience in the Arctic. Held in Rovaniemi, Finland, from 27-30 January 2019, the workshop brought together top scholars in cybersecurity risk assessment, governance, and resilience to discuss potential analytical and governing strategies and offer perspectives on how to improve critical Arctic infrastructure against various human and natural threats. The book is organized in three sections according to topical group and plenary discussions at the meeting on: cybersecurity infrastructure and threats, analytical strategies for infrastructure threat absorption and resilience, and legal frameworks and governance options to promote cyber resilience. Summaries and detailed analysis are included within each section as summary chapters in the book.The book provides a background on analytical tools relevant to risk and resilience analytics, including risk assessment, decision analysis, supply chain management and resilience analytics. It will allow government, native and civil society groups, military stakeholders, and civilian practitioners to understand better on how to enhance the Arctic’s resilience against various natural and anthropogenic challenges.

The use of Unmanned Aerial Vehicles (UAVs) or ‘drones’ continues to increase, and keeping up to date with technological, legal and commercial developments related to this domain is important, particularly with regard to safety and security in regional and border security operations. This book presents edited contributions from the NATO Advanced Training Course (ATC) entitled “Modern technologies enabling safe and secure UAV operation in urban airspace”, held in Agadir, Morocco, from 25 to 30 November 2019. Participants included experienced scientists and industry engineers involved in UAV development and activity, and the aim of the ATC was to increase awareness among all NATO and partner countries of the safety and security challenges raised by UAV flights in urban airspace, as well as sharing the knowledge and expertise of specialists working to advance the technologies and capabilities that will enhance safety and security across NATO and its partner countries. The ATC began with a presentation about current UAV technologies, and the technological features that might present a threat to the safety of commercial or military airspace applications. Other topics covered included the U-space concept; management of UAV operations in controlled airspace; integration of manned and unmanned aviation; testing and certification of UAVs; autonomous UAV flights; application of UAVs in urban airspace; and BVLOS flights and sensors for UAV navigation and communication. The book will be of interest to all those working with UAVs or seeking to develop and encourage their use, particularly for security purposes.

Damage to critical energy infrastructure as a result of terrorism, criminal activity or natural disaster can have a significant impact at both a national and international level. Reducing the vulnerability of critical infrastructure to protect populations is therefore a high priority for governments worldwide, and high-quality training courses and advanced technologies are imperative in this regard.This book presents edited contributions from the NATO Advanced Training Course (ATC) entitled ‘Critical Energy Infrastructure Protection: Innovative Structures and Materials for Blast and Ballistic Protection’, held as a virtual event from 22 - 25 March 2021. The principal aim of the course was to gather specialists from NATO member and partner countries interested in protecting their critical infrastructure against terrorist attacks, and to share research and practical experience in this field. The meeting provided a forum for participants and speakers to disseminate their recent work, and also served to promote the exchange of ideas and international cooperation among scientists and engineers. The focus was on the physical protection of critical infrastructure in the face of certain types of intentional threat or accident, such as explosions, impacts and blast waves, and the experts shared their experience on topics including the mitigation of risks, classification of vulnerabilities, improvement of resilience, advanced protective materials, dynamic testing of materials and structures, simulations, and numerical prediction methods.The book will be of interest to all those whose work involves protecting critical infrastructure from the threat of terrorist attacks.

Today’s security environment is increasingly complex and unpredictable, with cyber attacks and hybrid warfare blurring the lines between conventional and unconventional forms of conflict, threats to energy security such as climate change and natural disasters, and disruptive technologies like AI and quantum computing. The challenge of adapting and responding to these threats calls for cooperation and novel ways of thinking.This book presents 11 edited contributions from the NATO Advanced Training Course (ATC) Strengthening SEE Resilient Cyber Defense against Hybrid Threats (STRENGTH), held as an online event from 26 September – 02 October 2021. The ATC brought together more than 60 military and civilian expert participants with 19 renowned professors, experts and practitioners from 14 NATO Member and Partner countries as speakers and lecturers. The ATC aimed to raise awareness about the Alliance and the South Eastern Europe (SEE) evolving complex-threat environment and establish the foundation for a long-term multidisciplinary collaboration among defense and security experts and academia, with the event serving as a first step in the creation of a SEE Network of defense-security and academic experts which can work across borders, linking state of the art of research and practice to build resilience against hybrid warfare capabilities. Participants learned how state and non-state actors acquire hybrid threats via cyberspace to achieve their strategic ends, and took part in working groups, moderated by invited speakers/lecturers, engaging in the productive discussion of questions related to the course topic. The event concluded with briefings presenting relevant case studies and lessons learned.

Although cybersecurity is something of a latecomer on the computer science and engineering scene, there are now inclinations to consider cybersecurity a meta-discipline. Unlike traditional information and communication systems, the priority goal of the cybersecurity of cyber-physical systems is the provision of stable and reliable operation for the critical infrastructures of all fundamental societal functions and activities. This book, Cybersecurity for Critical Infrastructure Protection via Reflection of Industrial Control Systems, presents the 28 papers delivered at the NATO Advanced Research Workshop (ARW) hosted in Baku, Azerbaijan, and held online from 27-29 October 2021. The inspiration and motivation behind the ARW stem from the growth in large-scale cyber attacks, the rising degree of complexity and sophistication of advanced threats, and the need to protect critical infrastructure by promoting and building a resilient system to promote the well-being of all citizens. The workshop covered a wide range of cybersecurity topics, permeating the main ideas, concepts and paradigms behind ICS and blended with applications and practical exercises, with overtones to IoT, IIoT, ICS, artificial intelligence, and machine learning. Areas discussed during the ARW included the cybersecurity of critical infrastructures; its educational and research aspects; vulnerability analysis; ICS/PLC/SCADA test beds and research; intrusion detection, mitigation and prevention; cryptography; digital forensics for ICS/PLCs; Industry 4.0 robustness and trustworthiness; and Cyber Fortress concept infused with practical training. Investigating theoretical and practical problems involving the security of critical and essential infrastructure of each segment of contemporary societies, the book will be of interest to all those whose work involves cybersecurity.

The attention of many developed countries has increasingly focused on the security and protection of critical infrastructure. The use of Unmanned Systems (USs) for this purpose has been growing rapidly in recent years, as advances in technology, increased versatility and smaller size, together with the reduced risks and costs associated with removing the need for a pilot or operator on board, have all made these systems more attractive.This book, Monitoring and Protection of Critical Infrastructure by Unmanned Systems, presents 15 papers delivered at the NATO Advanced Training Course (ATC) of the same name hosted in Chisinau, the Republic of Moldova, from 30 May to 5 June 2022. This event was held in a hybrid format, and was attended in-person by 12 of the 31 speakers and the majority of the 92 attendees. The aim of the ATC was to explore the monitoring and protection of critical infrastructure using USs. Various USs, including ground control stations (GCS), data communication links, and a range of unmanned aerial (UAV), ground (UGV) and underwater (UUV) vehicles are covered, and the papers included here also deal with topics such as the use of drones for buildings inspection and the new technologies which can help with the recognition and monitoring of anthropogenic threats and natural hazards. There is also a focus on data analysis and modeling. Providing an overview of the use of unmanned vehicle systems and sensor-network technology for monitoring and protection, the book will be of interest to all those working to protect critical infrastructure.

The attention of many developed countries has increasingly focused on the security and protection of critical infrastructure. The use of Unmanned Systems (USs) for this purpose has been growing rapidly in recent years, as advances in technology, increased versatility and smaller size, together with the reduced risks and costs associated with removing the need for a pilot or operator on board, have all made these systems more attractive.This book, Monitoring and Protection of Critical Infrastructure by Unmanned Systems, presents 15 papers delivered at the NATO Advanced Training Course (ATC) of the same name hosted in Chisinau, the Republic of Moldova, from 30 May to 5 June 2022. This event was held in a hybrid format, and was attended in-person by 12 of the 31 speakers and the majority of the 92 attendees. The aim of the ATC was to explore the monitoring and protection of critical infrastructure using USs. Various USs, including ground control stations (GCS), data communication links, and a range of unmanned aerial (UAV), ground (UGV) and underwater (UUV) vehicles are covered, and the papers included here also deal with topics such as the use of drones for buildings inspection and the new technologies which can help with the recognition and monitoring of anthropogenic threats and natural hazards. There is also a focus on data analysis and modeling. Providing an overview of the use of unmanned vehicle systems and sensor-network technology for monitoring and protection, the book will be of interest to all those working to protect critical infrastructure.

The accelerating pace at which quantum computing is developing makes it almost inevitable that some of the major cryptographic algorithms and protocols we rely on daily, for everything from internet shopping to running our critical infrastructure, may be compromised in the coming years.This book presents 11 papers from the NATO Advanced Research Workshop (ARW) on Quantum and Post-Quantum Cryptography, hosted in Malta in November 2021. The workshop set out to understand and reconcile two seemingly divergent points of view on post-quantum cryptography and secure communication: would it be better to deploy post-quantum cryptographic (PQC) algorithms or quantum key distribution (QKD)? The workshop brought these two communities together to work towards a future in which the two technologies are seen as complementary solutions to secure communication systems at both a hardware (QKD) and software (PQC) level, rather than being in competition with each other. Subjects include the education of an adequate workforce and the challenges of adjusting university curricula for the quantum age; whether PQC and QKD are both required to enable a quantum-safe future and the case for hybrid approaches; and technical aspects of implementing quantum-secure communication systems. The efforts of two NATO nations to address the possible emergence of cryptanalytically-relevant quantum computers are explored, as are two cryptographic applications which go beyond the basic goal of securing two-party communication in a post-quantum world. The book includes economic and broader societal perspectives as well as the strictly technical, and adds a helpful, new contribution to this conversation.