Improved systems and techniques for secure delivery of data. One or more data providers deliver encrypted data to a storage entity. For each of one or more authorized recipients of data delivered by a data provider, the data provider generates a re-encryption key and delivers it to the storage entity. The storage entity uses a recipient's re-encryption key to re-encrypt data to be delivered to the recipient. The recipient is able to use its own key to decrypt data that has been encrypted with the data provider's key and re-encrypted with the re-encryption key of the recipient. Delivery of data may be managed to insure that it reflects a consistent condition. Data may be homomorphically encrypted by each of a plurality of data providers and processed in aggregate at the storage entity, with a recipient being able to decrypt the aggregated data but not individual elements of the aggregated data.