RFR: 8331008: Implement JEP 478: Key Derivation Function API (Preview) [v11]

[Valerie Peng]

On Tue, 13 Aug 2024 15:24:11 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).
>> 
>> Work was begun in [another PR](https://github.com/openjdk/jdk/pull/18924).
>
> Kevin Driver has updated the pull request incrementally with one additional commit since the last revision:
> 
>   addressed several review comments, namely: - renaming the getParameters method - renaming the AlgorithmParameterSpec object - address some javadoc exception messages - add some information to KDF class private constructor javadocs - other general cleanup

src/java.base/share/classes/com/sun/crypto/provider/HkdfKeyDerivation.java line 227:

> 225:                                                                       == null) ? null : salt.getEncoded());
> 226:                 pseudoRandomKey = new SecretKeySpec(extractResult, "RAW");
> 227:                 return Arrays.copyOf(hkdfExpand(pseudoRandomKey, info, length),

In the case of `length` is an exact multiples of hmac out length, we can return the output directly w/o the `Arrays.copyOf(...)` call, right?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20301#discussion_r1719173082