Aptible’s built-in Database Encryption is sufficient to comply with most data regulations, including HIPAA Technical Safeguards [45 C.F.R. § 164.312 (e)(2)(ii)], but we strongly recommend also implementing application-level encryption in your App to further protect sensitive data. The idea behind application-level encryption is simple: rather than store plaintext in your database, store encrypted data, then decrypt it on the fly in your app when fetching it from the database. Using application-level encryption ensures that should an attacker get access to your database (e.g. through a SQL injection vulnerability in your app), they won’t be able to extract data you encrypted unless they also compromise the keys you use to encrypt data at the application level. The main downside of application-level encryption is that you cannot easily implement indices to search for this data. This is usually an acceptable tradeoff as long as you don’t attempt to use application-level encryption on everything. There are, however, techniques that allow you to potentially work around this problem, such as Homomorphic Encryption.
📘 Don’t roll your own encryption. There are a number of libraries for most application frameworks that can be used to implement application-level encryption.

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Key Rotation

Application-level encryption provides two main benefits over Aptible’s built-in Database Encryption and Custom Database Encryption regarding rotating encryption keys.

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Key rotations are faster

Odds are, not all data is sensitive in your database. If you are using application-level encryption, you only need to re-encrypt sensitive data when rotating the key, as opposed to having to re-encrypt everything in your Database. This can be orders of magnitude faster than re-encrypting the disk. Indeed, consider that your Database stores a lot of things on disk which isn’t strictly speaking data, such as indices, etc., which will inevitably be re-encrypted if you don’t use application-level encryption.

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Zero-downtime key rotations are possible

Use the following approach to perform zero-downtime key rotations:
  • Update your app so that it can read data encrypted with 2 different keys (the old key, and the new key). At this time, all your data remains encrypted with the old key.
  • Update your app so that all new writes are encrypted using the new key.
  • In the background, re-encrypt all your data with the new key. Once complete, all your data is now encrypted with the new key.
  • Remove the old key from your app. At this stage, your app can no longer need any data encrypted with the old key, but that’s OK because you just re-encrypted everything.
  • Make sure to retain a copy of the old key so you can access data in backups that were performed before the key rotation