Stealing Keys from PCs using a Radio: Cheap Electromagnetic Attacks on Windowed ExponentiationWe demonstrate the extraction of secret decryption keys from laptop computers, by nonintrusively measuring electromagnetic emanations for a few seconds from a distance of 50 cm. The attack can be executed using cheap and readily-available equipment: a consumer-grade radio receiver or a Software Defined Radio USB dongle. [...]
We successfully extracted keys from laptops of various models running GnuPG (popular open source encryption software, implementing the OpenPGP standard), within a few seconds. The attack sends a few carefully-crafted ciphertexts, and when these are decrypted by the target computer, they trigger the occurrence of specially-structured values inside the decryption software. These special values cause observable fluctuations in the electromagnetic field surrounding the laptop, in a way that depends on the pattern of key bits (specifically, the key-bits window in the exponentiation routine). The secret key can be deduced from these fluctuations, through signal processing and cryptanalysis.
The counter: playing music. "Why did you guys have to have GnuPGP play 'Daisy, Daisy' when decrypting ciphertext? Isn't that a little creepy?"
This seems bogus given the following piece from the summary:
A quick scan of the actual paper reveals: "our examples use Lenovo 3000 N200 laptops, which exhibit a particularly clear signal." It appears as if this is not a general attack, but rather a flaw in specific pieces of hardware that should be addressed (possibly with some software mitigation).
It's feasible for many types of computer. It just sounds like they chose the strongest signal to establish a lower bound on how many samples are needed.
I was disappointed after realizing this article did not announce the resurrection of your Tempest arcade game.
PITMITM: a PITA in the man in the middle attack.