A secret (symmetric) key. The purpose of this interface is to group (and provide type safety for) all secret key interfaces.
Provider implementations of this interface must overwrite the equals and hashCode methods inherited from Object, so that secret keys are compared based on their underlying key material and not based on reference. Implementations should override the default destroy and isDestroyed methods from the Destroyable interface to enable sensitive key information to be destroyed, cleared, or in the case where such information is immutable, unreferenced. Finally, since SecretKey is Serializable, implementations should also override ObjectOutputStream.writeObject(java.lang.Object) to prevent keys that have been destroyed from being serialized.
Keys that implement this interface return the string RAW as their encoding format (see getFormat), and return the raw key bytes as the result of a getEncoded method call. (The getFormat and getEncoded methods are inherited from the Key parent interface.)