Whose keys are they anyway?
- By Garry McCracken
- Aug 27, 2015
Google recently announced enhanced security support for its cloud customers by granting them the ability to hold the encryption keys to their data. These customer-supplied encryption keys for the Google Cloud Platform follow the example set by other cloud industry leaders such as Amazon Web Services and Box and position the tech giant as an advocate for user data privacy.
The many federal IT managers who rely on Google Cloud and AWS are now able to develop a more sound security strategy when it comes to adopting the cloud. Government security managers running Google Cloud should educate themselves on the various cloud encryption models available and also consider which complementary security solutions must also be implemented. Depending on the cloud encryption model employed, cloud data may be susceptible to unauthorized access by cloud service provider insiders or be moved to other jurisdictions that might present data sovereignty issues.
Let’s break it down.
Server-side encryption. At the most basic level of the cloud encryption models, there is server-side encryption (SSE), where the encryption is performed by the cloud service provider using keys it owns and manages itself. Server-side encryption is the most vulnerable cloud encryption model, as the key unlocking access to the data is in control of the cloud provider. While SSE provides a basic level of encryption, it does not provide enterprise security control nor does it help protect against insider attacks because service provider employees could access the data intentionally or by mistake.
Server-side encryption with customer-provided keys. What Box, AWS and now Google offer is server-side encryption with customer-provided keys (SSE-CPK). In this model, the cloud provider handles the encryption but hands the keys the customer to own and manage. The cloud service provider runs the encryption in its underlying infrastructure and promises to only keep the keys in memory while the virtual machine is up and running. However, the keys still flow through cloud provider application programming interfaces, so it is not much of a stretch for the cloud provider to divert or intercept the keys.
Client-side encryption. The most secure solution is client-side encryption (CSE), which occurs in the cloud but it is initiated and managed by the data owner. The customer selects the encryption method and provides the encryption software. Most important, the customer owns and manages the encryption keys.
This approach allows customers to store and manage the keys for the virtual machines on their own premises or in a controlled instance in the cloud. When the virtual machine boots up in the private or public cloud, it can use a pre-boot network connection to an enterprise-controlled intelligent key manager to retrieve the key.
In the announcement of SSE-CPK on Google’s blog, the company chides, “Keep in mind, though, if you lose your encryption keys, we won’t be able to help you recover your keys or your data – with great power comes great responsibility!” The onus is indeed on the customer to not only keep the keys close, but keep them safe. The most responsible move for IT admin is to have an enterprise-controlled intelligent key management solution to manage crypto activities.
Google’s support for SSE-CPK is a step in the right direction to giving enterprises control over who accesses their data, but it still falls short of client-side encryption. Only with the CSE model – where both the encryption and keys are initiated and managed by the data owner, not the cloud provider – does the customer have the most protection and control possible in the cloud.
Garry McCracken is vice president of technology at WinMagic.