"ASK" is amplitude shift keying (shifting/changing between two amplitudes). In cheap transmitters (like the ones on keyfobs) one of the amplitudes commonly is "

"ASK" is amplitude shift keying (shifting/changing between two amplitudes). In cheap transmitters (like the ones on keyfobs) one of the amplitudes commonly is "on", the other "off". This is morse, literally the first modulation ever invented to be used with radio waves. Receivers for much more complicated modulation schemes have been built by amateurs for many decades, so I think in the case of analyzing the keyfobs' security SDRs were not a necessary tool. But of course with the advent of cheap Rx and Tx capable SDRs the amount of people able to decode (and transmit) all kinds of modulated signal in all kinds of frequency bands has exploded, and for example my ability to quickly change from running a cell-tower to receiving satellites signals to decoding/analyzing/transmitting the keyfob radiwaves and unlocking a car is only one "./configure ; make" away, once I have acquired a sufficiently advanced SDR. No need to build, solder, tune, debug an electronic circuit tediously custom built for one application.