Add support for X25519 algorithm alias to XDH

[exceptionfactory]

This pull request adds X25519 as a supported algorithm name alias for KeyPairGenerator, KeyFactory, and KeyAgreement implementations in the OpenSSLProvider.

Based on the work completed in PR #950 providing the X25519 implementation, this pull request allows integrating libraries to use the X25519 alias instead of XDH.

The alias references align with the JDK 11 implementation of Curve25519 Key Agreement described in JEP 324, which notes that referencing the specific algorithm name provides convenient shorthand for KeyAgreement and related components. It is also worth noting that the JDK 11 implementation returns XDH for calls to getAlgorithm() on generated keys, and this alias strategy follows the same convention.

[prbprbprb]

Thanks very much for this! I noticed it was missing but hadn't got around to it.

However, it should be done as an alias rather than a top-level entry, e.g. instead of

        put("KeyPairGenerator.X25519", PREFIX + "OpenSSLXDHKeyPairGenerator");

you need

        put("Alg.Alias.KeyPairGenerator.X25519", "XDH");

and so on. That way you should need fewer test changes too.

Are you OK with making this change?

[exceptionfactory]

Thanks for the review and feedback @prbprbprb!

I adjusted the alias settings to use the appropriate Alg.Alias names. I also removed most of the unit test changes and rebased from the current master branch.

I retained the X25519 Key Agreement test and related test changes, but if you don't think that is necessary, I can also remove it as well.

[prbprbprb]

Awesome, thanks for the quick turnaround!

[prbprbprb]

Good news, you can use that in source builds right away. Bad news, the earliest it will be available in the Android platform is November.

Plus we plan a maven release "soon" once we finish figuring out Gradle issues.

[exceptionfactory]

Good news, you can use that in source builds right away. Bad news, the earliest it will be available in the Android platform is November.

Plus we plan a maven release "soon" once we finish figuring out Gradle issues.

Thanks again @prbprbprb!