POSEIDON deals with the protection of outsourced or mutualized data and content. With the fast expansion of the Internet and associated services, content/data protection mechanisms have recently been the focus of huge interest, especially cryptographic and information hiding techniques (digital watermaking and active fingerprinting). These techniques greatly help in tackling some traditional security issues: copyright protection (cryptography, watermaking,fingerprinting), content/data confidentiality (cryptography through encryption, fragmentation,access control), content/data integrity (cryptography through digital signature or message authentication codes, watermaking), authentication of entities (cryptography), anonymity (anonymous networks or granting), and privacy (cryptography, k-anonymity and its extensions, and the more recent differential privacy).

These mechanisms are known to be efficient when used independently. However, in many situations they have to be combined. To illustrate this point, we can consider a company or a hospital that outsources its data and/or services. It may want to split up the data stored on outsourced servers, in order to preserve confidentiality. It may also want to watermark them so as to embed some robust proof of authenticity, or to anonymise some of their components in order to preserve privacy. Hence, these mechanisms must be combined in an appropriate way to provide the security functionalities without one harming the other.

Security issues are formalized through a security policy, which clearly specifies the entities involved in the system, the data and services to protect, the threats, security properties and actions which are required to protect them. To apply these rules, we rely on several security mechanisms such as those listed above, and their combination is essential to tackle all the security issues properly (e;g; copyright protection in a Video On Demand application; confidentiality in mutualized storage on an outsourced server; privacy, confidentiality and copyright protection in social networks).

Outsourced content/data protection hence lean on three pillars.

•  A formal expression of the security policy.
• The design of security mechanisms on which the security policy relies; we therefore need to formalize the security properties each security mechanism can ensure. This formalization must of course be compliant with the one of the security policy.
• The extension of this formalism in order to properly state the consequences of the combination os several such mechanisms. This is essential to enable an automated deployment of the poliy: automated selection of the mechanisms depending on the context and related security priorities, automated analysis of possible incompatibilities.

In this context, POSEIDON will then work on:

• The efficient combination of different security mechanisms,
• The systematic formalization of security properties guarenteed by the involved security mechanisms, in particular when these mechanisms are combinated,
• automating the choice of mechanisms to be deployed. An issue especially important in the context of growing data/content outsourcing practices.

This work will lean on the interactions between:

• SFIIS team of the Lab-STICC: security policies and databaeses security (Frédéric Cuppens and Nora Cuppens-Boulahia), cryptography, digital watermaking and active fingerprinting (Caroline Fontaine);
• The LaTIM: Protection of medical multimedia content – medical image and medical database watermarking, Integrity control and blind forensics (Gouenou Coatrieux);
• IRISA and INRIA/University Rennes 1/Supélec joint-team CIDRE: content security and self-configurable networks (ad hoc and peer-to-peer) security (Nicolas Prigent) and privacy (Sébastien Gambs) ;
• IRISA: databases and databases watermaking (David Gross-Amblard).