IIRC, Sagan specifically mentioned that our radio signals are being beamed out into space (long ago, in the TV series Cosmos.) The probability of decoding NTSC

IIRC, Sagan specifically mentioned that our radio signals are being beamed out into space (long ago, in the TV series Cosmos.) The probability of decoding NTSC signals (ie, the old SD standard) without prior knowledge is probably going to be better than decoding the current digital MPEG broadcast standard. So the aliens have about 50 years of signals to look at before it suddenly looks like we encrypted everything. I hope they like reruns of Mr Ed.