Conventional meaningful image sharing methods have defects in pixel expansion

and distributed cover images have low visual quality. To address these problems

a (

) 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. In the sharing phase

the secret image is converted into difference and location maps by adjusting difference transformation. The (

)-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 (

)-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 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. 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. 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.