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 300:

> 298:         }
> 299:         Mac hmacObj = Mac.getInstance(hmacAlgName);
> 300:         hmacObj.init(new SecretKeySpec(salt, "HKDF-Salt"));

Why use "HKDF-Salt" as key algorithm name? This is just internal key for the Hmac object and maybe it's safer to just use the `hmacAlgName` as the key algorithm? The key algorithm does not affect the Hmac operation anyway.

src/java.base/share/classes/com/sun/crypto/provider/HkdfKeyDerivation.java line 312:

> 310:      * Perform the HMAC-Expand operation.  At the end of the operation, the
> 311:      * keyStream instance variable will contain the complete KDF output based on
> 312:      * the input values and desired length.

These lines are outdated? I can't find any `keyStream` instance variable.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20301#discussion_r1719073308
PR Review Comment: https://git.openjdk.org/jdk/pull/20301#discussion_r1719075233