Cloud computing refers to the ability to access and manage information stored on remote servers, using any Internet-enabled platform, including smart phones. In the cloud, any user can can access and/or remotely store respective data with minimal management effort or service provider interaction. Without the knowledge of the physical location of the server or how the processing of sensitive and personal data is confgured, end users consume cloud services without any information about the processes involved. This brings about issues related to security, privacy and trust. This paper proposes a combined solution based on threshold group-oriented signatures TGOS and threshold multisignature (TMS) as a secure and efficient access to cloud services. The proposal is a privacy-presereving third-party auditing protocol, independent of data encryption and with a focus on security for data storage.