Abstract. Inner product functional encryption (IPFE) is a promising advanced cryptographic primitive for the inner product function
class that facilitates fine-grained access control of sensitive data in an
untrusted cloud environment and has an expanding range of applications in the context of cloud security, health-record access control, network privacy, data security on mobile devices, Internet of Things (IoT)
and many more. We address the open problem of constructing public key
unbounded IPFE (UIPFE) schemes that do not use bilinear pairings. Our
main results are as follows:
– We design the first post-quantum secure public key UIPFE scheme in
the random oracle model with adaptive security based on the Learning With Errors (LWE) assumption with leads to low computation
cost.
– Furthermore, we develop a public key unbounded zero inner product
predicate IPFE (UZP-IPFE) scheme that allows a successful decryption if an inner product policy is satisfied. We support the conjectured security of our candidate by analysis and prove that the
scheme achieves security in the selective weak attribute-hiding model
under the LWE assumption. The scheme offers linear-size ciphertext and constant-size secret keys. We emphasize that our construction presents the first post-quantum secure UZP-IPFE scheme in an
unbounded scenario preserving attribute-hiding property.
More interestingly, when contrasted with the existing similar schemes,
all our schemes exhibit favourable results in terms of communication
overhead and secret key size.
