Stealth ABBE: Carry-Free Homomorphic Packing and Blind Reed–Solomon Decoding

Classical Broadcast Encryption (BE) and Attribute-Based Broadcast Encryption (ABBE) schemes suffer from three fundamental bottlenecks in zero-trust and censorship-prone environments: (i) severe header bloat scaling with the number of authorized or revoked subsets, (ii) the explicit transmission of plaintext revocation lists and access structures that leak recipient metadata to Deep Packet Inspection (DPI), and (iii) prohibitive re-keying overhead during dynamic group membership updates. In this paper, we generalize the A-scheme to establish a novel framework for Stealth Attribute-Based Broadcast Encryption. Instead of encrypting session keys across combinatorial subset trees, bilinear pairings, or rigid binary-cube topologies (such as CuBES), our architecture encodes a monolithic session payload once into a non-systematic Reed–Solomon (RS) codeword encapsulated within an additively homomorphic elliptic curve layer. Each broadcast participant possesses a dense attribute vector acting as an algebraic error-correcting key; only nodes whose attribute intersection with the broadcast policy satisfies the $k$-out-of-$n$ syndrome decoding threshold can reconstruct the session key. By combining information-theoretic blinding masks with constant-time point-to-uniform steganographic mappings under the STAC (Stealth Transport via Algebraic Coding) paradigm (via Elligator 2 on Curve25519 or explicit inverse isogenies with Elligator Squared on pairing-friendly curves), the broadcast stream is rendered statistically indistinguishable from uniform noise, completely eliminating visible headers and revocation lists. Finally, we demonstrate that the carry-free property of Base-3 homomorphic packing enables instantaneous, on-the-fly epoch mutations, allowing dynamic user revocation and policy shifts without re-keying legitimate participants or overflowing the underlying scalar ring.