@Override
    protected void engineInitSign(PrivateKey privateKey) throws InvalidKeyException {
        this.privateKey = (OpenSslMlDsaPrivateKey) privateKey;
        this.publicKey = null;
        buffer.reset();
    }
Buffer to hold value to be signed or verified.
common/src/main/java/org/conscrypt/OpenSslSignatureMlDsa.java