HankG wrote:
While tuning through 20 meters, I came across a transmission on 14.1730 at
17:50 UTC. As I tried to bring in the station, I realized that it was
encrypted.

It ended abruptly at 17:53 and started again at 17:57. Not your typical ham
QSO.

Is encryption allowed by hams?
no

but how can you telling it was encrypted

Not knowing the HF Band plan it could have been one of the various
digtal mode to go on and off as you describe could simply have been a
qso where you could only hear one station instead of both

HankG