随着信息安全技术的不断发展，传统信息载体的研究已颇为成熟，但仍存在份额易 篡改、载荷量小且无法抵抗字节流攻击等缺陷，因此急需新的信息载体开辟崭新的研究方向。QR 码为上述问题提供了新思路，它不仅可以作为标签，又可以作为数字水印的载体图像，并在各类场景中得到广泛应用。本篇论文对基于多级安全二维码的秘密共享机制进行研究，以 QR 码作为研究载体构造具有身份锁的秘密共享方案和自适应的视觉 密码共享方案，设计一个秘密载荷量高且更具有实用性的多级安全二维码。

      针对文字秘密信息，现有的多秘密共享方案中，不同秘密具有相同的访问控制结构，且字节流传输过程中易遭受主动攻击。为了避免上述缺点，首先本文提出具有身份锁的 门限多秘密共享方案，身份锁只能由授权子集打开；其次，二维码为秘密信息提供纠错机制，超过纠错率时秘密信息才会失效。同时方案中子秘密可重复被使用、欺骗行为可被检测且不增添参与者的信息交互；最后，基础子份额分发算法是基于会话密钥协商算 法，不需预设安全通道传输秘密子份额。与其他方案相比，本文方案具有更高的安全性及实用性，适用于视频会议、文件分发等具有身份权限访问控制需求的应用场景。

      针对图像秘密信息，目前基于 QR 码的视觉加密方案主要基于平均灰度映射技术， 在恢复复杂秘密图像时会出现图像失真现象。为了避免上述缺点，首先本文提出一种基 于 QR 码的新型自适应视觉密码共享方案，构造两种不同自适应算法改善图像的失真问题；其次，方案还改进了二维码共享矩阵的生成算法，保留通过轻量级异或运算可快速恢复秘密图像的优点；最后，设计了随机分布的秘密向量，保证单个秘密共享份不会泄露秘密图像的任何信息。此外，改进后的算法降低秘密向量的空间复杂度，降低非法攻击的可能性。与其他方案相比，本文的方案能清晰地恢复图像，适用于秘密图像更复杂的场景，具有更好的安全性和实用性。

       本文结合具有身份锁的门限多秘密共享方案和自适应的视觉秘密共享方案，对二维码进行分级处理，同时嵌入文字秘密信息和图像秘密信息，设计一个基于多级安全二维码的秘密共享机制，增大秘密载荷量，并提高了 QR 码作为载体的安全性。

      With the continuous development of information security technology, the research of traditional information carriers has been quite mature, but there are still defects such as easy to tamper with the share, small load and unable to resist byte stream attacks, so there is an urgent need for new information carriers to open up a new research direction. QR code provides a new idea for the above problem, which can be used as both a label and a carrier image for digital watermark, and has been widely used in various scenarios. This thesis focuses on the research of secure QR code based on multi-level secret sharing, constructing a secret sharing scheme with identity lock and an adaptive visual password sharing scheme with QR code as the research carrier, and designing a multi-level secure QR code with large secret load and more practicality.

        For textual secret information, the existing multi-secret sharing schemes in which different secrets have the same access control structure and are vulnerable to active attacks during byte stream transmission. To avoid the above drawbacks, Firstly, this paper proposes a gated multi-secret sharing scheme with identity lock, which can only be opened by an authorized subset; Secondly, the QR code provides an error correction mechanism for the secret information, and only when the error tolerance limit is reached, the secret information will break its validity. At the same time, the scheme does not increase the information interaction of any participant while maintaining the reusability of sub-secrets and detectable spoofing; Finally, based on the session key negotiation algorithm, the scheme does not require a preset secure channel to transmit the secret sub-share, which better ensures the security and practicality of the scheme. Compared with other schemes, the scheme is very suitable for video conferencing, file distribution and other gated multi-secret sharing scenarios based on identity authority access control.

          For image secret information, the current visual encryption scheme based on QR code is still gated, and the existing scheme is mainly implemented by average gray mapping, which will be distorted when recovering complex secret images. To avoid the above drawbacks, Firstly, we propose a new adaptive visual secret sharing scheme based on QR codes, and constructs two different adaptive algorithms to improve the distortion problem of secret image recovery; Secondly, the schemes also improves the generation algorithm of QR code sharing matrix, which retains the advantage that the secret image can be recovered quickly through lightweight heterogeneous operation; Finally, the secret vectors in the scheme are uniformly distributed, while a single shared QR code does not disclose the secret image information. In addition, the improved algorithm reduces the space consumed by the secret vector and decreases the probability of being subject to illegal attacks. Compared with other schemes, the scheme in this paper can recover clearer secret images and is suitable for scenarios where secret images are more complex, with better security and practicality.

           In this paper, we simultaneously combine the threshold multi-secret sharing scheme with identity lock and the adaptive visual secret sharing scheme, perform hierarchical processing on the QR code, use the QR code to embed both text secret information and image secret information, and design a secure QR code based on multi-level secret sharing, which increases the amount of secret load and improves the security of the carrier at the same time.