Description:

The file specified by the --keyFile or security.keyFile option is now a YAML file instead of a plain text file. This should be fully backwards compatible with old keys and all the same rules about key formats (base64 characters only with whitespace stripped) are still in place, but the underlying file format is YAML now (i.e. you could escape characters or even add comments) . This is in preparation for supporting multiple keys during the keyfile rollover procedure.

Engineering Ticket Description:

As part of the keyfile rollover project we'll need to support loading multiple keys from disk. This ticket changes the format of the keyfile to YAML to support that.