[wakawaka28]

There's only a couple of cases where this can go wrong. Either the contents of what is being sent out could be wrong, or the hardware itself could be tampered with to extract extra information on another optical or radio channel. Both of these require extensive software tampering. In the simple case where you trust the software on both sides, and the hardware, this can be practically as good as it gets (with the requirement that the inside be monitored automatically somehow).