RFR: 8297878: KEM: Implementation

[Xue-Lei Andrew Fan]

On Thu, 13 Apr 2023 19:01:24 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

>> Currently, `provider()` is a method of `KEM.Encapsulator`. If `KEMSpi. newEncapsulator` also returns this interface, then what value should its `provider()` method return? This is what I meant registering itself to a provider.
>> 
>> When I said different instances, I was asking
>> 
>> var k = KEM.getInstance("DHKEM", p);
>> var e = k.newEncapsulator(pk);
>> // now, is p == e.provider()?
>> 
>> 
>> Or, are you suggesting we should define `provider()` somewhere else? It's possible, but I have difficulty making every class immutable.
>
>> Currently, `provider()` is a method of `KEM.Encapsulator`. If `KEMSpi. newEncapsulator` also returns this interface, then what value should its `provider()` method return? This is what I meant registering itself to a provider.
>> 
>> When I said different instances, I was asking
>> 
>> ```
>> var k = KEM.getInstance("DHKEM", p);
>> var e = k.newEncapsulator(pk);
>> // now, is p == e.provider()?
>> ```
>> 
>> Or, are you suggesting we should define `provider()` somewhere else? It's possible, but I have difficulty making every class immutable.
> 
> If the provider() method in KEM.Encapsulator is the only reason, the cost to support it may be too high with so many duplicated/similar specifications/names and code.
> 
> Option 1: Remove the KEM.Encapsulator.provider() method, and provide no access to the underlying provider object.
> 
>>  do you expect it to return new SunJCE()? This means the p in getInstance("DHKEM", p) will be a different instance from the value returned by getProvider(). 
> 
> The Provider class is mutable, we may not want to change the provider object asked for "DHKEM".  I think you have used a solution to pass the provider object in the KEM.java implementation currently.  Maybe, it could be twitted a little bit so that the provider can be passed to a delegated KM.Encapsulator interface implementation.
> 
> Option 2:
> 
> public final class KEM {
>     interface Encapsulator {
>         ...
>         KEM.Encapsulated encapsulate(...);
>         ...
>         
>         default Provider provider() {
>             return null;
>         }
>     }
>     
>     private static class DelegatedEncapsulator implements Encapsulator {
>         private final Provider p;
>         private DelegatedEncapsulator(Encapsulator e, Provider p) {
>             this.p = p;
>             ...
>         } 
>         public Provider provider() {
>             return this.p;
>         }
>     }
> 
>     ...
>           KEMSpi spi = (KEMSpi) service.newInstance(null);
>           return new DelegatedEncapsulator(
>                        spi.engineNewEncapsulator(pk, spec, secureRandom),  // This is the interface implementation, use the same provider as KEM.
>                 service.getProvider());    // This is the provider passed to the delegated KEM.Encapsulator object.
>     ...
> }

For more details about option 2, please refer to https://github.com/openjdk/jdk/pull/13470/files.  The KEM.java and KEMSpi.java is pretty much the same except the clean up of En/Decapsulator(s) in this PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13256#discussion_r1166057562