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I think everyone agrees that if you are going to move data to a cloud (unless it is your own private cloud) it must be encrypted and even then it should be carefully considered.
Most home Internet backups, from various vendors, provide the encryption key. I currently have two backup vendors for my home PCs, being the paranoid person that I am. But I honestly let both vendors handle the encryption.
That might be fine for home backups but it’s not going to be okay for operational usage with tens to thousands of users for any small medium or large company for daily data not backup. The issues are large and complex when deciding what to do or not to do with key management, and your goal needs to be to protect your data and meet all legal requirements (Sarbanes/Oxley, HIPPA, etc).
Here is what I see the issues are:
1) Who controls the keys and has access to them?
2) How do users interface with their keys and what happens when a user leaves?
3) When do the keys get applied to the data?
4) Who is responsible if bad things happen?
The first question I would ask a cloud service provider is: can they read my data?
If the cloud provider has access to the keys by providing the key management system, you need to be concerned if there is any possible way that a rogue employee with access to the keys and the systems could access your data.
If this is even a potential you likely need to determine if you have legally liability if it happens. More than likely if you are aware of the remote possibility, you are likely liable if, say, someone accesses patient records.
Let’s say that you are responsible for key management. In that case there are a variety of questions to ask.
For example, do you have the experience and understanding of the key management system to administrate it?
What happens if the administrator leaves or goes rogue? What needs to happen in an organization is a very solid well thought out plan to ensure that no one person has all of the information and knowledge. Temper that with the knowledge that if everyone has access to the keys, the only thing you’re protecting yourself from is the cloud – provided that none of your staff are selling the keys on the black market.
Key management control needs to be well designed and well thought out for the long term if you are going to move data to the cloud. You cannot assume that everyone will stay forever. Most important, I think that companies have the responsibility to manage and control their encryption policy – this should not be left to the cloud vendor, given the potential liability.
I see a number of types of user issues, chiefly:
1) How do users interface with their keys and what happens when a user leaves?
2) Is the system simple enough for the non-technical employee?
3) What if a user forgets their key?
4) What if a user changes their key and does not tell you and leaves?
Any key management system must allow for all levels of skills and computer knowledge. It must address issues of file ownership after someone leaves or is on extended leave, for example.
Who has the right to look at the files and who does not have the rights? How are accesses logged, such that you know if someone is sharing keys or there is an attempt to break in and get your files? Is the key management logging safe from a smart hacker? What happens if a user forgets their keys? We all can forget stuff, or there could be a medical issue or physical reason (head injury, for example) that causes this. What are the processes and procedures when this happens? You of course do not want users writing down the keys on Post-It Notes. It is not if, it is when a user forgets their keys – at which point it will be too late to institute a procedure.
The last issue I listed is about the malicious user and how you control what happens if they change keys and do not tell you. San Francisco learned this the hard way with their network passwords (see the case of the rogue admin). You need to think about the possible events and the required outcome to ensure that your operations are protected against this event.
When do the keys get applied to the data?
One of the questions I always ask is: when do the keys get applied to the data? And that leads to a related question, which is: when are hash checked to ensure that the data is not corrupted?