Post 2 of 6 in the series on building Anyhide , a Rust steganography tool. This post is about a small feature that multiplies your adversary's work by a factorial. I like features that give you an outsized security improvement for very little code. Multi-carrier encoding is one of those. The implementation is maybe twelve lines. The effect is that the set of carriers you use becomes an ordered secret — and getting that order wrong produces deterministic garbage, which an attacker can't distinguish from using the wrong files entirely. Let me explain. The single-carrier recap In a normal Anyhide flow, both parties share one file. They use it as a reference, and the sender encodes a message by computing byte positions into that file. Single file, single shared secret. But "the carrier is the file we both have" is a constraint I wanted to relax. What if the carrier is a set of files ? What if the set is ordered, and the order itself is a secret nobody but the two parties knows? That's multi-carrier encoding.…