Functional Encryption
Functional encryption (FE) generalizes ABE/IBE: the key is tied to a function f, and decryption outputs f(m) rather than m, disclosing only the function’s value.
Purpose
It enables fine-grained data access where key holders obtain only specific function values of the data, never the raw data.
Mechanism
A key sk_f is tied to function f, and Decrypt(sk_f, Enc(m)) = f(m). An identity f gives standard encryption, a predicate f gives predicate encryption, and an inner-product f gives inner-product FE. General FE builds on multilinear maps or FHE.
Use cases
- Restricted data access
- Privacy-preserving statistical queries
- Encrypted machine learning