Yes, data can be secured in the cloud and the confidence level depends on the security schemes used. Hence, one cannot make any comment regarding the security of data unless the scheme is known.

For more details, kindly read the following articles:

https://www.researchgate.net/publication/258205564_Incremental_Proxy_Re-encryption_Scheme_for_Mobile_Cloud_Computing_Environment?ev=prf_pub

https://www.researchgate.net/publication/256182274_A_Study_of_Incremental_Cryptography_for_Security_Schemes_in_Mobile_Cloud_Computing_Environments?ev=prf_pub

https://www.researchgate.net/publication/257666298_Enhanced_dynamic_credential_generation_scheme_for_protection_of_user_identity_in_mobile-cloud_computing?ev=prf_pub

Hope that helps

Article Incremental Proxy Re-encryption Scheme for Mobile Cloud Comp...

Conference Paper A Study of Incremental Cryptography for Security Schemes in ...

Article Enhanced dynamic credential generation scheme for protection...

Providing highly secure access authentication allows us to keep the cloud data secure, while establishing strong confidence in the cloud data security, because any user (including malicious hacker) has to perform identity authentication with a remote authentication server before being authorized access to the cloud data.

(1) Cloud Security Alliance (CSA) is a not-for-profit organization with a mission to “promote the use of best practices for providing security assurance within Cloud Computing, and to provide education on the uses of Cloud Computing to help secure all other forms of computing”. Currently CSA has the following Working groups and initiatives: Mobile Working Group Big Data Working Group Security as a Service Working Group Trusted Cloud Initiative CloudAudit CloudCERT CloudSIRT Cloud Metrics Security, Trust & Assurance Registry (STAR) Cloud Data Governance http://en.wikipedia.org/wiki/Cloud_Security_Alliance

You can find the useful documents on cloud data security from the following official website of Cloud Security Alliance. https://cloudsecurityalliance.org/

(2) To address potential vulnerabilities of traditional password authentication, idQ® Enterprise digital identity platform has been developed to provide passwordless access authentication for cloud data. -- Cryptographic algorithms have been applied to establish trust relationship among a user, an endpoint device, a remote authentication server, and a web/cloud application (or a cloud storage/resources). -- idQ distributed zero-password authentication and authorization system is the first-ever passwordless digital identity platform where a digital identity can’t be stolen, because no shared secret and no private key are stored anywhere including endpoint devices.

Zero-Password Authentication and Authorization System https://www.researchgate.net/project/Zero-Password-Authentication-and-Authorization-System