RFR: 8331008: Implement JEP 478: Key Derivation Function API (Preview) [v77]

[Alan Bateman]

On Wed, 15 May 2024 19:59:59 GMT, Kevin Driver <kdriver at openjdk.org> wrote:

>> Introduce an API for Key Derivation Functions (KDFs), which are cryptographic algorithms for deriving additional keys from a secret key and other data. See [JEP 478](https://openjdk.org/jeps/478).
>
> Kevin Driver has updated the pull request incrementally with one additional commit since the last revision:
> 
>   javadoc formatting

> > * The KDF.deriveXXX methods mention "Delayed provider selection". Is this idempotent? If I create a KDF and several threads race to derive keys or data, is it guaranteed that the same provider will be selection for any ordering of these threads?  What does KDF::getProviderName if no provider has been selected?
> 
> I believe it would _not_ be guaranteed that the same provider would be selected for any ordering of the threads (depending on their possibly unique KDFParameterSpec values). Is this a documentation call-out? Or did you have a concern about this?

It means that a KDF is stateful and mutable. It may be thread safe but it would be a hazard to attempt to use a shared instance. So I think there is a bit of a design smell here, something to look at for the next preview. The behaviour of KDF::getProviderName with delayed provider selection is very surprising. It may be that this method has to throw IllegalStateException when not bound to a provider.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/18924#issuecomment-2114096567