HKDF and/or PBKDF2 support for generating AES keys

[Wavesonics]

The ability to provide a client and server secret to generate a key would be very helpful.

Some pseudo code:

    shared_secret = server_secret + client_secret

    hkdf = HKDF(
        algorithm=SHA256(),
        length=key_length,
        salt=salt,
    )
    
    aes_key = hkdf.derive(shared_secret)

[whyoleg]

0.4.0 was just released!
PBKDF2, ECDH and HKDF are now available via secret derivation and shared secret derivation APIs.

[Wavesonics]

amazing, that was fast!