RFR: 8349946: Cipher javadoc could describe AEAD reuse better

[Anthony Scarpino]

On Sat, 7 Jun 2025 05:24:40 GMT, Sebastian Stenzel <duke at openjdk.org> wrote:

>> The class documentation in javax.crypto.Cipher could better describe AEAD and reuse. The current class description example is outdated as GCM encryption does not allow resets. The doc should state that reset() may not be possible with some algorithms or providers and that an InvalidAlgorithmParameterException is thrown
>
> src/java.base/share/classes/javax/crypto/Cipher.java line 117:
> 
>> 115:  * forgery attacks due to Key and IV uniqueness requirements.
>> 116:  * An {@link IllegalStateException} will be thrown when calling {@code update}
>> 117:  * or {@code doFinal} methods when a reset did not occur.
> 
> It might be helpful to describe what to do instead:
> 
> When reset is not possible, you don't need to dispose the cipher object. Instead you can call init again with a different key/nonce.

I suggest appending the sentence:  "{@code init} may re-initialize the {@code Cipher} object with new parameters".

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PR Review Comment: https://git.openjdk.org/jdk/pull/25399#discussion_r2136696481