public void init(PublicKey recipientKey, byte[] info, PrivateKey senderKey)
            throws InvalidKeyException {
        if (senderKey == null) {
            throw new InvalidKeyException("Sender private key is null");
        }
        // Remaining argument checks are performed by the SPI
        spi.engineInitSender(
                recipientKey, info, senderKey, HpkeSpi.DEFAULT_PSK, HpkeSpi.DEFAULT_PSK_ID);
    }
Initialises this HpkeContextSender in AUTH mode, i.e. messages are authenticated using
the sender's public key.

@param recipientKey public key of the recipient
@param info additional application-supplied information, may be null or empty
@param senderKey private key of the sender
@throws InvalidKeyException if either recipientKey or senderKey are null
        or an unsupported key format
@throws UnsupportedOperationException if mode is not a supported HPKE mode
@throws IllegalStateException if this HpkeContextSender has already been initialised
common/src/main/java/org/conscrypt/HpkeContextSender.java