The security of customer data is Snowflake’s first priority. All customer data is encrypted using industry-standard techniques such as AES-256. Encryption keys are organized hierarchically, rooted in a hardware security module (HSM). This allows complete isolation of customer data and greatly reduces the attack vectors.
For customers with the highest security requirements, we are adding another security component: customer-managed keys. With customer-managed keys, the customer manages the encryption key and makes it available to Snowflake. The customer has full control over this key. If the customer disables access to the encryption key, Snowflake can no longer access the customer’s data. Your data. Your encryption keys.
More Control over Data Access: Customer-managed keys make it impossible for Snowflake to comply with requests to access customer data. If data is encrypted using customer-managed keys and the customer disables access to the encryption key, it is technically impossible for Snowflake to decrypt the data. It is therefore the customer’s responsibility to comply with such requests directly.
Stop Data Breaches: If a customer experiences a data breach, they may disable access of customer-managed keys to Snowflake. This will halt all running queries in Snowflake, including queries that may inspect data or unload data. Disabling customer-managed keys allows customers to stop ongoing exfiltration of their data.
More Control over Data Lifecycle: The last reason why customers require this feature is lack of trust with any cloud provider. Customers may have sensitive data that they do not trust Snowflake to manage on their own. Using customer-managed keys, such sensitive data is ultimately encrypted with the customer’s key. It is impossible for Snowflake to decrypt this data without the customer’s consent. The customer has full control over the data’s lifecycle.
Before we explain the implementation of customer-managed keys, we should first give a background of Snowflake’s key hierarchy and Amazon’s key management service.
Snowflake manages encryption keys hierarchically. Within this key hierarchy, a parent key encrypts all of its child keys. When a key encrypts another key, it is called “wrapping”. When the key is decrypted again, it is called “unwrapping”.
Figure 1 shows Snowflake’s hierarchy of encryption keys. The top-most root keys are stored in a hardware security module (or CloudHSM). A root key wraps account master keys. Each account master key corresponds to one customer account in Snowflake. Account master keys, in turn, wrap all data-level keys, including table master keys, stage master keys, and result master keys. In addition, every single data file is encrypted with a separate key. A detailed overview of Snowflake’s encryption key management is given here.
Amazon’s AWS Key Management Service (KMS) is a service to store encryption keys and tightly control access to them. Amazon provides an audit log of all operations and interactions with KMS by using CloudTrail. This allows customers to manage their own encryption keys and validate their usage via the audit log. KMS also allows customers to disable access to any keys at any time. Combining KMS with Snowflake’s encryption key hierarchy allows us to implement customer-managed keys. More details about AWS KMS can be found here.
