RFR: 8325448: Hybrid Public Key Encryption [v20]

[Sean Mullan]

On Thu, 28 Aug 2025 11:55:13 GMT, Weijun Wang <weijun at openjdk.org> wrote:

> > > Hi Sebastian, the API you suggested is only the KEM step, and it should be made internal inside HPKE.
> > > At the end of the day, HPKE is still a cipher. I understand the key encapsulation message (aka, KEM ciphertext) is different from a traditional IV, but they share some key characteristics: 1) generated by the sender after initialization, 2) cryptographically random, 3) then made public, 4) has critical impact on encryption result.
> > 
> > 
> > To avoid some of this potential confusion, I think it could help to expand on the description of `Cipher.getIV()` to describe this new use case for IV, something like changing this sentence:
> > "This is useful in the case where a random IV was created, or in the context of password-based encryption or decryption, where the IV is derived from a user-supplied password."
> > to:
> > "This is useful in the case where a random IV was created, or in the context of password-based encryption or decryption, where the IV is derived from a user-supplied password, or in the case of HPKE (Hybrid Public Key Encryption) where IV contains the encapsulation of the KEM shared secret."
> 
> Good idea. Somehow I hesitate to update the base spec directly. Shall we put the whole paragraph into an `@apiNote`? A similar paragraph also appears in `CipherSpi::engineGetIV`.

Yes, making this text an API note, which is what it really is, is a really good idea.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/18411#issuecomment-3233362526