Multi-authority Distributed Attribute-Based Encryption with application to Searchable Encryption on lattices

Many Internet users deploy several cloud services for storing sensitive data. Cloud services provide the opportunity to perform cheap and efficient storage techniques. In order to guarantee secrecy of uploaded data, users need first to encrypt it before uploading it to the cloud servers. There are also certain services which allow user to perform search operations according to certain attributes without revealing any information about the encrypted content. In the cryptographic community this service is known as the public key encryption with keyword search. In order to enable user control during performed search operations there exists an attribute-based encryption scheme that provides the required functionality. We introduce the first Key-Policy Multi-Authority Attribute-Based Encryption (KP-MABE) on lattices assuming existence of multiple servers, where each of these servers contributes to the decryption process by computing decryption shares using its own secret share. Furthermore we construct a Key-Policy Distributed Attribute-Based Searchable Encryption (DABSE) which is based on lattices and use the introduced KP-MABE as a building block for the transformation to DABSE. We prove our scheme secure against chosen ciphertext attacks under the assumption that the underlying KP-MABE is secure under the hardness of learning with errors (LWE) problem.