Focusing on the malicious cheating behaviors of Third Party Auditor （TPA） in cloud audit， a trusted cloud auditing scheme without bilinear pairings was proposed to support the correct judgment of the behaviors of TPA. Firstly， the pseudo-random bit generator was used to generate random challenge information， which ensured the reliability of the challenge information generated by TPA. Secondly， the hash value was added in the process of evidence generation to protect the privacy of user data effectively. Thirdly， in the process of evidence verification， the interactive process between users and TPA results was added. The data integrity was checked and whether TPA had completed the audit request truthfully or not was judged according to the above results. Finally， the scheme was extended to realize batch audit of multiple data. Security analysis shows that the proposed scheme can resist substitution attack and forgery attack， and can protect data privacy. Compared with Merkle-Hash-Tree based Without Bilinear PAiring （MHT-WiBPA） audit scheme， the proposed scheme has close time for verifying evidence， and the time for generating labels reduced by about 49.96%. Efficiency analysis shows that the proposed scheme can achieve lower computational cost and communication cost on the premise of ensuring the credibility of audit results.

Aiming at the low embedding capacity of Reversible Data Hiding （RDH） in encrypted videos， a high-capacity RDH scheme in encrypted videos based on histogram shifting was proposed. Firstly， 4×4 luminance intra-prediction mode and the sign bits of Motion Vector Difference （MVD） were encrypted by stream cipher， and then a two-dimensional histogram of MVD was constructed， and （0，0） symmetric histogram shifting algorithm was designed. Finally， （0，0） symmetric histogram shifting algorithm was carried out in the encrypted MVD domain to realize separable RDH in encrypted videos. Experimental results show that the embedding capacity of the proposed scheme is increased by 263.3% on average compared with the comparison schemes， the average Peak Signal-to-Noise Ratio （PSNR） of encrypted video is less than 15.956 dB， and the average PSNR of decrypted video with secret can reach more than 30 dB. The proposed scheme effectively improves the embedding capacity and is suitable for more types of video sequences.