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"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," explained Genkin and his colleagues in a paper detailing their work. "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."Genkin and his colleagues designed their gadget to fit inside a pita bread to illustrate that attackers could use this method against targets in public places, such as restaurants and cafeterias, without drawing attention to themselves. The only restriction is that they would need to be no farther than 50cm from their target laptop. The security researchers were able to crack the encryption key in a matter of seconds, they go on to report in their paper. To read more about how attackers can use radio waves to steal users' data, including on airgapped computers, please click here.