RFR: 8331008: Implement JEP 478: Key Derivation Function API (Preview) [v15]

[Sean Mullan]

On Fri, 23 Aug 2024 21:48:44 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:
> 
>   code review comments and test renaming

src/java.base/share/classes/javax/crypto/KDF.java line 84:

> 82:  *                              .addSalt(salt).thenExpand(info, 32);
> 83:  *
> 84:  *    kdfHkdf.deriveKey("AES", derivationParameterSpec);

Should show what is returned, i.e. `SecretKey key = ...`

src/java.base/share/classes/javax/crypto/spec/HKDFParameterSpec.java line 142:

> 140:          *     if {@code length} is not greater than 0
> 141:          */
> 142:         public ExtractThenExpand thenExpand(byte[] info, int length) {

If it is a fairly common use case to not have an `info` parameter, then I think we should add a method that does not take this parameter, i.e. `thenExpand(int length)`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20301#discussion_r1732589985
PR Review Comment: https://git.openjdk.org/jdk/pull/20301#discussion_r1732593180