RFR: 8314323: Implement JEP 527: TLS 1.3 Hybrid Key Exchange [v6]

[Sean Mullan]

On Wed, 15 Oct 2025 06:48:50 GMT, Hai-May Chao <hchao at openjdk.org> wrote:

>> Implement hybrid key exchange support for TLS 1.3 by adding three post-quantum hybrid named groups: X25519MLKEM768, SecP256r1MLKEM768, and SecP384r1MLKEM1024.
>> Please see [JEP 527](https://openjdk.org/jeps/527) for details about this change.
>
> Hai-May Chao has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Revert changes to UseStrongDHSizes test as ffdhe6144/8192 added back
>  - Updated comment in ServerHello and hybrid to upper-case in NamedGroup

test/jdk/sun/security/ssl/CipherSuite/RestrictNamedGroup.java line 1:

> 1: /*

Question: does disabling "x25519" also disable "X25519MLKEM768"? It probably should not. I think both groups would need to be specified in order to disable both. Please add a test for this case.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27614#discussion_r2478574748