The Internet has evolved from a mere communication network used by tens of millions of users twodecades ago, to a global multimedia platform for communication, social networking, entertainment,education, trade and political activism used by more than two billion users. This transformation hasbrought tremendous benefits to society, but has also created entirely new threats to privacy, safety,law enforcement, freedom of information and freedom of speech. In today’s Internet, principals areamorphous, identities can be fluid, users participate and exchange information as peers, and data isprocessed on global third-party platforms. Existing models and techniques for security and privacy,which assume trusted infrastructure and well-defined policies, principals and roles, fail to fully addressthis challenge.The imPACT project addresses the challenge of providing privacy, accountability, compliance andtrust (PACT) in tomorrow’s Internet, using a cross-disciplinary and synergistic approach to understandingand mastering the different roles, interactions and relationships of users and their joint effect onthe four PACT properties. The focus is on principles and methodologies that are relevant to the needsof individual Internet users, have a strong potential to lead to practical solutions and address the fundamentallong-term needs of the future Internet. We take on this challenge with a team of researchersfrom relevant subdisciplines within computer science, and with input from outside experts in law,social sciences, economics and business. The team of PIs consists of international leaders in privacyand security, experimental distributed systems, formal methods, program analysis and verification, anddatabase systems. By teaming up and committing ourselves to this joint research, we are in a uniqueposition to meet the grand challenge of unifying the PACT properties and laying a new foundation fortheir holistic treatment.