CLARUS - A Framework for User Centred Privacy and Security in the Cloud

Focus Area

Although cloud computing offers many benefits to its users, security issues such as confidentiality and privacy are still major concerns to those intending to migrate to the cloud. Traditional cloud security has been based on assurance to customers that cloud providers follow sound security practices. As a result, current security mechanisms are commonly located within the cloud platform, hence compelling customers to trust cloud providers. However, customers might be reluctant to outsource sensitive data due to lack of control over data storage and management. To reach its full potential, cloud computing needs solid security mechanisms that enhance trust in cloud computing by allowing cloud customers a greater control on the security and privacy of their data.

The main objective of the CLARUS project [1] is to enhance trust in cloud computing services by developing a secure framework for the storage and processing of data outsourced to the cloud that allows end users to monitor, audit and control the stored data without impairing the functionality and cost-saving benefits of cloud services.

Market sector targets

The beneficiaries of the CLARUS solution will be, on the one side, potential cloud customers like companies, public organisations and e-government administrations, which could thereby be motivated to embrace the benefits of trusted cloud services while retaining full control over any potentially sensitive data they outsource to the cloud. On the other side, the cloud providers themselves can also benefit because a trust-enabling solution like CLARUS will widen the spectrum of potential cloud users, which implies a market opportunity for cloud providers. In the long term, initiatives like CLARUS can pave the way to developing more transparent, standardised, auditable and controllable cloud services, which will be beneficial for all stakeholders.

Addressing key concerns impeding the mainstream adoption of the cloud: privacy, security, trust

Enhancing privacy, security and trust of end users with respect to the cloud providers is the main goal of the CLARUS project. To achieve this, the CLARUS solution is envisioned as a proxy located in a domain trusted by the end user (e.g., a server in her company’s intranet, a plug-in in the user’s device) that implements security and privacy-enabling features towards the cloud service provider.

To enhance privacy, CLARUS will implement a set of privacy-enabling mechanisms to ensure that the user’s sensitive data are properly protected before they are outsourced to the cloud. Protection will be provided in a way that cloud service functionalities are still preserved, even those that require performing operations (e.g., queries, transformations, calculations) on the protected data. To achieve that, CLARUS will rely on and innovate over the current state of the art on functionality-preserving cryptographic (e.g., (partially) homomorphic encryption, searchable encryption, etc.) and non-cryptographic data protection techniques (e.g., data anonymisation, document redaction, data splitting and merging, private information retrieval, etc.), with a special focus on preserving the benefits associated with cloud services (functionality, cost-effectiveness, efficiency, etc.).

To enhance trust, CLARUS will also implement a set of auditing services, so that users can directly supervise how data are being protected and outsourced to the cloud. To enhance security, CLARUS will also develop an attack-tolerant framework, so that potential security breaches within the cloud can be dynamically detected and appropriate mitigation measures can be activated on-line.

In this way, the user’s privacy, security and trust can be significantly enhanced with respect to current cloud security solutions both regarding honest-but-curious cloud providers and potential attackers (insiders as well as outsiders), while still preserving cloud functionalities (within the Platform-as-a-Service, Infrastructure-as-a-Service and Software-as-a-Service models).

Interoperability and portability: existing and emerging standards that can foster trust in the cloud

The CLARUS project proposes to develop the above-described framework as a set of generic protocols that can be used by collaborative cloud service providers in order to build trusted cloud services that are standardised and, therefore, transparent with regard to data management, privacy and security.

To do so, within the CLARUS project, a set of communication interfaces and protocols will be designed: i) between the end user and the CLARUS proxy, ii) among different CLARUS instances running at different organisations, and iii) between the CLARUS proxy and the cloud service providers. The aim is that the interfaces and protocols should be generic and cover most of the spectrum of cloud services, so that they can be proposed as cloud standards. By means of standardisation, protocols and functions can be made homogenous for cloud providers and CLARUS proxies, so that: i) interoperability can be achieved among otherwise heterogeneous cloud providers; ii) collaborative services (e.g., edition of documents outsourced to the cloud by several users) can be implemented through several CLARUS proxies; and iii) APIs based on standards can be made available to programmers for a seamless development of end-user cloud-based applications.

How is cloud disrupting the market?

Cloud computing certainly provides great benefits to end users, but it has been built on the assumption that appropriate security and privacy-preserving techniques are implemented by cloud providers. However, recent security breaches of well-known cloud services (e.g., Sony Playstation Network outage, Apple iCloud celebrity photos leakage) have revealed the risks of uncontrolled data outsourcing; as a result, the trust of end users in cloud services has been seriously undermined and users with really sensitive data (e.g. healthcare data) are extremely reluctant to outsourcing them. As highlighted by the European Commission and several Cloud-related working parties [2-4], a model change is needed to tackle this serious issue. The new model should return to data owners the control over their data and should foster cloud services based on standards that can be certified as compliant with security and privacy.

Links and references

[1] CLARUS Project.

[2] European Commission. What does the Commission mean by secure Cloud computing services in Europe? Press Release Database. Brussels, 15 October 2013. Available at:

[3] European Commission. Unleashing the Potential of Cloud Computing in Europe. Brussels, 27 September 2012. Available at:

[4] ETSI. Cloud Standards Coordination. Final report. November 2013. Available at:,d.d24&cad=rja