RIP computer security
"Acoustic. The power consumption of a CPU and related chips changes drastically (by many Watts) depending on the computation being performed at each moment. Electronic components in a PC's internal power supply, struggling to provide constant voltage to the chips, are subject to mechanical forces due to fluctuations of voltages and currents. The resulting vibrations, as transmitted to the ambient air, create high-pitched acoustic noise, known as "coil whine," even though it often originates from capacitors. Because this noise is correlated with the ongoing computation, it leaks information about what applications are running and what data they process. Most dramatically, it can acoustically leak secret keys during cryptographic operations.
By recording such noise while a target is using the RSA algorithm to decrypt ciphertexts (sent to it by the attacker), the RSA secret key can be extracted within one hour for a high-grade 4,096-bit RSA key. We experimentally demonstrated this attack from as far as 10 meters away using a parabolic microphone (see Figure 1) or from 30cm away through a plain mobile phone placed next to the computer."
h/t +Christopher Tate