People are increasingly using Cloud storage – both in their professional and private lives, thus making data security an increasing concern. Companies and schools have been increasing their use of services like Google Drive for some time, and lots of individual users also store files on Dropbox, Box, Amazon Drive, Microsoft OneDrive and the like. The concern about keeping information private is a big one – and keeping millions of potential users from storing data online once they were more certain of its security.
The good news is that data stored in the Cloud is nearly always stored in an encrypted form that would need to be cracked before an intruder could read the information. However, the location of where the encryption key is stored varies from one Cloud storage service to the next (implying different levels of security). Also, there are somewhat simple ways users themselves can improve the security of their data stored in the Cloud.
The key that turns gibberish into meaningful data can be stored by the Cloud service itself or by individual users. Most services keep the key themselves, letting their systems see and process user data, such as indexing data for future searches. These services also access the key when a user logs in with a password, unlocking the data so the person can use it.
This is a much more convenient option than having users keep the keys themselves. But it is also less secure – just like regular keys, if someone else has them, they might be stolen or misused without the data owner knowing. And some services might have flaws in their security practices that leave users’ data vulnerable.
Some (less popular) Cloud services require users to upload and download files through service-specific client applications that include encryption functions. That extra step lets users keep the encryption keys themselves. For that additional security, users forgo some functions, such as being able to search among their Cloud-stored files.
Bear in mind that these services aren’t perfect either – there’s still a possibility that their own apps might be compromised or hacked, allowing an intruder to read clients’ files either before they’re encrypted for uploading or after being downloaded and decrypted. An encrypted Cloud service provider could even embed functions in its specific app that could leave data vulnerable. And, of course, if a user loses the password, the data is irretrievable.
One new mobile app says it can keep phone photos encrypted from the moment they’re taken, through transmission and storage in the Cloud. Other new services may arise offering similar protection for other types of data, though users should still be on guard against the potential for information to be hijacked in the few moments after the picture is taken, before it’s encrypted and stored.
To maximize Cloud storage security, it’s best to combine the features of these various approaches. Before uploading data to the Cloud, first encrypt it using your own encryption software. Then upload the encoded file to the Cloud. To get access to the file again, log in to the service, download it and decrypt it yourself.
This, of course, prevents users from taking advantage of many Cloud services, like live editing of shared documents and searching Cloud-stored files. And the company providing the Cloud services could still modify the data, by altering the encrypted file before you download it.
The best way to protect against that is to use authenticated encryption. This method stores not only an encrypted file, but also additional metadata that lets a user detect whether the file has been modified since it was created.
Ultimately, for people who don’t want to learn how to program their own tools, there are two basic choices:
1) Find a Cloud storage service with trustworthy upload and download software that is open-source and has been validated by independent security researchers.
2) Use trusted open-source encryption software to encrypt your data before uploading it to the Cloud; these are available for all operating systems and are generally free or very low-cost.
Think very hard about the security of your data when considering using a Cloud service to store it – convenience aside, do what you can to keep the data in your hands.