GnuPG is prone to a side-channel attack by using acoustic cryptanalysis against the computer running it. While this flaw is not in GnuPG itself, this attack is demonstrated against it due to the prevalence and perceived security. By examining the audio emissions of a laptop computer, certain encryption functions can be deduced due to the core processor noise. Such attacks can be carried out covertly via a mobile phone placed very close to the computer, or from a greater distance (e.g. several meters) using a more sensitive microphone. This attack can allow for the full recovery of a 4096-bit RSA decryption key, considered to be extremely strong, in about an hour.
