RFR: 8353578: Refactor existing usage of internal HKDF impl to use the KDF API [v8]

[Valerie Peng]

On Sat, 10 May 2025 14:30:16 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> src/java.base/share/classes/sun/security/util/KeyUtil.java line 451:
>> 
>>> 449:                 || alg.equalsIgnoreCase("Generic");
>>> 450:     }
>>> 451: 
>> 
>> As you know, I've been working on the [TLS Exporters change]( https://github.com/openjdk/jdk/pull/24976) which will use the same KDF APIs.  I've already updated that to use your style.  
>> 
>> Looks like I've now got one more thing to change!  ;)
>
> This is a reply to the comment above. I don't know why GitHub does not show a reply box there.
> 
>> Is any specific salt needed here like in TLS?
> 
> In DHKEM, the salt used is always empty.

So, no need to explicitly set it I assume? As this is a refactoring, I prefer to minimize changes unless consensus is different.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24393#discussion_r2085631201