A side channel attack breaks cryptography by using information leaked by cryptography, such as monitoring the electromagnetic field (EMF) radiation emitted by a computer screen to view information before it’s encrypted in a van Eck phreaking attack. Other well-known side channel attacks include spying on the power consumption of an electronic device to steal an encryption key, or acoustic attacks that record the sound of a user’s key strokes to steal their passphrase. TEMPEST attacks work because screens emit EMF radiation that can be sniffed from as far as hundreds of meters away (and certainly from across the street)”]