This paper presents Quantum Gatekeeper, a context-bound image steganography framework where successful payload recovery depends on both cryptographic decryption and the reconstruction of a precise extraction path. The system integrates lossless least significant bit (LSB) embedding with a deterministic variational quantum circuit (VQC)-derived gate key, multi-factor contextual binding, and authenticated encryption. Payload extraction is contingent upon four requisite factors: a password, a shared secret, a user-supplied context string, and a reference image signature. Any deviation in these factors causes the system to read from an incorrect pixel sequence or fail authentication, resulting in silent rejection rather than partial disclosure. The proposed method derives a gatecontrolled extraction key from a seed-conditioned variational circuit, with parameters generated via cryptographic hash expansion and context-dependent image features. To ensure encode/decode consistency, the cryptographic key path is generated via exact statevector simulation; concurrently, IBM superconducting quantum hardware is utilized to evaluate the statistical behavior of the circuit family under physical noise. We introduce a dual-region image layout to resolve the nonce bootstrapping dependency, separating header recovery from payload recovery through independently derived keys. Experimental results confirm successful end-to-end message embedding and recovery on PNG images, demonstrating deterministic success under correct conditions and failure otherwise. The framework supports both text and image payloads; in the image-in-image configuration, a secret image is resized to a fixed resolution prior to embedding, enabling exact pixel-level recovery under correct contextual reconstruction.

翻译：本文提出量子看门人（Quantum Gatekeeper）框架，这是一种上下文绑定的图像隐写方法，其中有效载荷的成功恢复既依赖于密码学解密，也依赖于精确提取路径的重建。该系统将无损最低有效位（LSB）嵌入与确定性变分量子电路（VQC）导出的门控密钥、多因子上下文绑定以及认证加密相结合。有效载荷的提取取决于四个必要因子：密码、共享密钥、用户提供的上下文字符串以及参考图像签名。任何因子的偏差将导致系统读取错误的像素序列或认证失败，从而以静默拒绝而非部分披露的方式作出响应。所提方法通过种子条件变分电路导出门控抽取密钥，密钥参数通过密码学哈希扩展与上下文相关的图像特征生成。为确保编解码一致性，密码学密钥路径通过精确状态向量仿真生成；同时利用IBM超导量子硬件评估电路族在物理噪声下的统计行为。我们引入双区域图像布局以解决随机数引导依赖问题，通过独立推导的密钥将头部恢复与有效载荷恢复分离。实验结果表明，该方法在PNG图像上实现了端到端的消息嵌入与恢复，在正确条件下呈现确定性成功，否则失败。该框架支持文本与图像两类有效载荷；在图像中嵌图像配置下，秘密图像在嵌入前被缩放到固定分辨率，从而在正确上下文重建时实现精确像素级恢复。