GetDatabaseEngine returns the database engine correspo.

RegisterDatabaseEngine registers a database engine.

PublicKey is the key type for getting a public keys.

SigningKey is the key type used internally by the HKP server to sign submitted user public keys.

Config is a generic config type for database used essentially during YAML configuration parsing, so database engines are free to implement their own configuration requirements.

Engine defines interface that database engines must implement.

KeyType defines the type of key to be stored in the database.