Only xs and t are sent. Even if a hacker intercepts the data, without knowing the exact sensing matrix used to produce xs, he/she cannot reconstruct the original signal.
In this demo app, data between the sender and the receiver is transmitted via the HTTP POST protocol.

Optional: Tamper with the sensing matrix.

To verify the security of this system, users are allowed to tamper with the sensing matrix in Step 3 "Signal Reconstruction".
With a changed sensing matrix, you will find that you can no longer correctly reconstruct the signal.