Information processed by businesses, government organizations and individuals often comes with confidentiality and integrity requirements that the processing party must adhere to. As a result, data processors must deploy security controls for their ICT infrastructure, protecting it against external as well as internal attackers. This is relatively easy when this infrastructure is local and controlled by the processing party, but much harder when it is provided by an external service provider. Cloud services promise great benefits in terms of financial savings, easy and convenient access to data and services, as well as business agility. Organizations and individuals therefore choose to outsource their data to the cloud, where an untrusted party is in charge of storage and computation. A major concern for the adoption of cloud computing is the inability of the cloud to build user trust in the information security measures deployed in cloud services. Common computing techniques cannot be applied on encrypted data, and therefore the data and the programs that compute on the data must be decrypted before being run on the cloud infrastructure. A comprehensive solution for securing the cloud computing infrastructure can be based on cryptographic mechanisms of secure computation. These mechanisms allow for distributed computation of arbitrary functions of private (secret) inputs, while hiding any information about the inputs to the functions. Put differently, these mechanisms support computation on encrypted data. We identify several settings where secure computation in the cloud is needed. PRACTICE will address all of these settings:

• Hiding user data from other users of the same cloud service.
• Hiding user data from the cloud provider
• Securing computation between several servers
• Securing computation between untrusting parties