Multi-User Multi-Key Image Steganography with Key Isolation

TL;DR

This paper introduces PUSNet-MK, a multi-user image steganography network that enforces strict key isolation, enabling secure multi-user secret embedding and recovery without cross-key leakage.

Contribution

It extends PUSNet to support multiple keys with a mismatched-key isolation loss, enhancing security in multi-user steganography scenarios.

Findings

High-quality stego images generated

Accurate secret recovery achieved

Effective prevention of cross-key decoding

Abstract

Steganography conceals secret information within innocuous carriers while preserving visual fidelity and enabling reliable recovery. Recent unified networks operate normally under untriggered conditions but switch to hidden steganographic tasks when triggered. PUSNet follows this paradigm by performing image purification during normal operation and steganographic embedding when activated. However, it supports only a single user with one key pair, limiting its applicability in multi-user settings. We propose PUSNet-MK, a multi-key extension that enforces strict key isolation via a mismatched-key isolation loss, effectively preventing cross-key decoding when a wrong key is applied. This design preserves the intended steganographic behavior while addressing a critical security limitation of PUSNet. Extensive experiments demonstrate that PUSNet-MK produces high-quality stego images and accurate secret recovery, while preventing unintended information leakage.