Encryption and Key Management – “Bring Your Own” to the Cloud

In this age of “Bring Your Own”, we see the acronyms BYOD (device), BYOE (encryption), and BYOK (key) showing up all over the blog-o-sphere. BYOK is a cloud computing security model that allows cloud service customers to use the provided server-side encryption software and (bring) manage their own encryption keys.

The idea of encryption (cryptography) is almost as old as the concept of written language: if a message might fall into enemy hands, then it is important to ensure that they will not be able to read it. Most typically, encryption relies on some sort of "key" to unlock and make sense of the message it contains, and that transfers the problem of security to a new level – now the message is secure, the focus shifts to protecting the key. In the case of access to cloud services, if we are encrypting data because we are worried about its security in an unknown cloud, then why would we trust the same cloud to hold the keys without using a key management solution?

BYOK can help an organization that wishes to take advantage of cloud services to address both regulatory compliance and data privacy concerns in a third-party multi-tenant environment. This approach allows a customer to use the encryption technology that best suits the customer's needs, including the cloud provider's underlying IT infrastructure. For example, Amazon’s Simple Storage Service (S3) is about protecting data-at-rest using server-side encryption with customer-provided encryption keys (SSE-C) or “BYOK”. With the encryption key you provide as part of your data request, Amazon S3 then manages the encryption (as it writes to disks) and decryption (when you access your data). You don't need to maintain any code to perform data encryption and decryption in S3. The only thing you do is manage the encryption keys you provide to the Amazon Simple Storage Service. When you upload an object, Amazon S3 uses the encryption key you provide to apply AES-256 encryption to your data and then removes the encryption key from memory. When you retrieve data, you must provide the same encryption key as part of your data request. Amazon S3 first verifies that the encryption key you provided matches, and then decrypts the data before returning it to you.

Important to Note: Amazon S3 does not store the encryption key you provide. Instead, they store a randomly salted HMAC value of the encryption key in order to validate future requests. The salted HMAC value cannot be used to derive the value of the encryption key or to decrypt the contents of the encrypted object. That means, if you lose the encryption key, you lose the object.

Any time a company decides it wants to host its applications in the cloud, or use a SaaS application where the company’s data will be stored in the cloud, their IT security professionals have to ask a series of questions.

• Can we encrypt the data? If so, who will have access to the keys?
• How will we perform key rotation and manage the lifecycle of the encryption keys?
• Is the cloud vendor using a proprietary encryption technology that prevents us from moving our data to another vendor?
• If we use 10 SaaS applications, will we have to administrate 10 different key management solutions?

These questions are tough enough to answer when the data and encryption technologies are in a company’s own data center where it has complete control over everything. In many cases, if encryption is provided, the cloud provider holds or has access to the keys, which creates another set of problems for the end user. For one thing, a third-party having access to data in the clear is a violation of regulations such as PCI-DSS, HIPAA, GLBA and others. Also, customers have yet to establish trust in cloud platforms or SaaS providers to protect their data. There have been many high profile data breaches that make end-users nervous. Customers also fear the U.S. government will subpoena access to their data without their knowledge or permission. For companies outside the U.S. that choose to use a U.S.-hosted cloud or app, there are data privacy and residency concerns. Instinctively it feels a lot more secure to manage your own key and use BYOK instead of leaving it to the cloud provider.

A few things have become crystal clear:

1. You need to know where your sensitive information is. Period.
2. You need to know who has access to it. Not who you think has access to it, but who really has access to it.
3. Wherever you put your sensitive information, you need to protect it. The most critical thing you need to do is to apply a strong defense in depth approach to data security, including the use of encryption and access controls.
4. You need to be able to document, through audit logs and reports, who has actually accessed your information. This is true (and important) for sensitive data, as well as for compliance-regulated data.
5. If you think that having your cloud service provider encrypt your data provides adequate security for your information, you probably need to rethink this.

It all boils down to this: When encrypted data is stored or processed in the cloud, the data and the keys must be kept separate and only the end-user should control the encryption keys.

Cloud storage options bring new economies and business efficiencies, but security can’t be ignored, and it can’t be simply outsourced to some other party. We believe that it is fundamental to good security to control all access to your data, including managing your own encryption keys. Managing encryption keys may sound daunting, but it doesn’t need to be. Our technology makes data security and encryption key management simple and straightforward. Our key management solution addresses all of the issues described above and can protect your data everywhere you have it stored.