目的 针对传统有意义分存方法存在的像素扩张和分发掩体图像视觉质量不高等问题,提出一种结合调整差值变换的(K,N)有意义图像分存方案,该方案可用于与掩体等大且同为自然图像的密图分存.方法 在分存阶段,首先用调整差值变换将密图转换为差值图和位置图;其次将差值图和位置图进行(K,N)分存,分别嵌入到掩体图像中,并使用密钥确定位置图分存信息的嵌入位置和根据位置图中不同的差值类型选择不同的差值嵌入方法;再次对密钥进行(K,N)分存,将子密钥和分发掩体对应的MD5值公布到第3方公信方作为认证码;最后将子密钥和分发掩体分发给参与者进行保管.在恢复阶段,首先核对参与者的子密钥和分发掩体对应的MD5值,若认证通过的人数小于K,则恢复失败;否则,使用认证通过的子密钥还原出密钥,然后根据密钥提取并恢复出位置图;其次根据位置图中的差值类型来提取和恢复出差值图;最后使用逆调整差值变换还原出最终密图.结果 同现有方法相比,所提策略不存在像素扩张且分发掩体图像视觉质量较高,具有较强的恶意参与者检测能力.结论 本文方法的掩体图像与密图等大且同为自然图像,同经典有意义图像分存方案相比,克服了像素扩张问题,嵌入信息后的掩体图像具有较高的视觉质量,使用第3方公信方存储的MD5值作为认证码,具有较强的恶意参与者识别能力.

Objective Conventional meaningful image sharing methods have defects in pixel expansion, and distributed cover images have low visual quality. To address these problems, a (K, N) meaningful image sharing scheme based on adjusting difference transformation is proposed. The size of the secret image is equal to that of each cover image, and the secret and cover images are both natural.Method In the sharing phase, the secret image is converted into difference and location maps by adjusting difference transformation. The (K, N)-threshold is used to share the respective difference and location maps and then embed them into cover images. In this step, a secret key is used to produce the embedded positions of the location map in cover images and to choose different embedding methods for various difference sharing data using the location map. Third, the (K, N)-threshold is used to share the secret key to the sub-secret keys. Finally, each sub key with its corresponding distributed cover image is managed by a participant, and their MD5 value is published into the third trust party. In the recovering phase, the MD5 value of each participant sub key with its cover image is checked. If less than K participants pass authentication, the recovering phase fails. Otherwise, the correct sub keys are used to recover the secret key before the location map is extracted and recovered by the secret key. Then, the location map is used to extract and recover the difference map. Finally, the secret image is recovered by inverse adjusting difference transformation with the location and difference maps.Result Experimental results show that the proposed scheme does not cause any defects in pixel expansion in comparison with conventional methods. The distributed cover images have satisfactory visual quality, and any malicious participants can be detected.Conclusion The secret image in the proposed scheme has the same size as the cover image, and both secret and cover images are natural. The distributed cover images have better visual quality with a strong malicious participant authentication capability by using MD5 as an authentication code.