  Access control encryption (ACE) enforces, through a sanitizer as the
mediator, that only legitimate sender-receiver pairs can communicate, without
the sanitizer knowing the communication metadata, including its sender and
recipient identity, the policy over them, and the underlying plaintext. Any
illegitimate transmission is indistinguishable from pure noise. Existing works
focused on computational security and require trapdoor functions and possibly
other heavyweight primitives. We present the first ACE scheme with
information-theoretic security (unconditionally against unbounded adversaries).
Our novel randomization techniques over matrices realize sanitization
(traditionally via homomorphism over a fixed randomness space) such that the
secret message in the hidden message subspace remains intact if and only if
there is no illegitimate transmission.
