The server can be configured to encrypt a message's payload when storing them, providing encryption at rest. This can be done from the command line or from the configuration file. Check encrypt and encryption_key in the Configuring section.
It is recommended to provide the encryption key through the environment variable NATS_STREAMING_ENCRYPTION_KEY instead of encryption_key. If encryption is enabled and NATS_STREAMING_ENCRYPTION_KEY is found, this will take precedence over encryption_key value.
You can pass this from the command line this way:
$ env NATS_STREAMING_ENCRYPTION_KEY="mykey" nats-streaming-server -store file -dir datastore -encrypt
We currently support two ciphers for encryption: AES and CHACHA. The default selected cipher depends on the platform. For ARM, we use CHACHA, otherwise we default to AES. You can always override that decision by explicitly specifying the cipher like this:
$ env NATS_STREAMING_ENCRYPTION_KEY="mykey" nats-streaming-server -store file -dir datastore -encrypt -encryption_cipher "CHACHA"
or, to select AES:
$ env NATS_STREAMING_ENCRYPTION_KEY="mykey" nats-streaming-server -store file -dir datastore -encrypt -encryption_cipher "AES"
Note that only message payload is encrypted, all other data stored by NATS Streaming server is not.
When running in clustering mode (see below), the server uses RAFT, which uses its own log files. Those will be encrypted too.
Starting a server with encrypt against a datastore that was not encrypted may result in failures when it comes to decrypt a message, which may not happen immediately upon startup. Instead, it will happen when attempting to deliver messages to consumers. However, when possible, the server will detect if the data was not encrypted and return the data without attempting to decrypt it. The server will also detect which cipher was used to encrypt the data and use the proper cipher to decrypt, even if this is not the currently selected cipher.
If the data is encrypted with a key and the server is restarted with a different key, the server will fail to decrypt messages when attempting to load them from the store.
Performance considerations: As expected, encryption is likely to decrease performance, but by how much is hard to define. In some performance tests on a MacbookPro 2.8 GHz Intel Core i7 with SSD, we have observed as little as 1% decrease to more than 30%. In addition to CPU cycles required for encryption, the encrypted payload is bigger, which result in more data being stored or read.