Multi-input Functional Encryption

We will talk about recent advances on multi-input function encryption, an emerging cryptographic paradigm that allows fine-grained access control over encrypted data. Functional encryption schemes [BSW 11] allow to generate restricted decryption keys sk_f associated with a function f, which can be used on a ciphertext Enc(x) to decrypt f(x), while keeping any other information about x private. Multi-input functional encryption [GGGJKLSSZ 14] generalizes this paradigm to a setting where n encryption slots are explicitly given, in the sense that a user who is assigned the i-th slot can, independently, create a ciphertext Enc(x_i) from his own plaintext x_i. Given ciphertexts Enc(x_1),..., Enc(x_n), one can use a secret key sk_f to retrieve f(x_1,..., x_n). This allows to compute functions on encrypted, distributed data, thereby reconciling confidentiality with useful data-mining. We present efficient, standard based constructions of multi-input functional encryption schemes for the inner product functionality [AGRW 15, ACFGB 17].