Attacks and improvements on Data Integrity as a Service protocols

Recently, Nepal et al. proposed the Data Integrity as a Service (DIaaS) protocols which focus on the integrity of data in cloud. These protocols were defined in four different scenarios and the authors claimed they were secure based on the proposed cloud storage service architecture. However, we find the fatal attacks on the protocols. To deal with these attacks, we present the improvements on the protocols to actually ensure the data integrity. In addition, we use Diffie-Hellman key exchange agreement to consult session key which is used to ensure the confidentiality of messages in data downloading stage. The security analysis shows our improved protocols can hold all the merits of the original protocols and have better security.