Tokenization along with encryption is store data securely in the cloud. Tokenization is when sensitive information is replaced with an independent value (token). Those tokens can be assigned or randomly generated and are next to imposable to track back, since they have no direct relation with the data you are temporarily replacing.
Here's one of the explanations on how tokenization is implemented in the cloud. "Cloud computing security issues include preserving confidentiality and privacy of data. The primary solutions for these problems include encryption or tokenization of data stored in the cloud. New solutions have emerged for improving cloud security and protecting sensitive data and important applications. One solution is the cloud encryption gateway, which helps enterprises address cloud security issues. The gateway can serve as a proxy “entry” to a cloud application, replacing sensitive data with encrypted or tokenized values for transmission and storage in the cloud. Since the sensitive information remains under corporate control at all times, organizations can confidently make the move to the cloud without the associated privacy, security and regulatory concerns of placing sensitive data with external cloud service providers."