It's unthinkably difficult to separate the decryption signal from all the other tasks the computer is performing at any given time
Sigh. No, it isn't. Please familiarize yourself with current research in the field.
There are plenty of plausible attack scenarios under which general-purpose systems are coaxed into executing mostly the vulnerable code, over a sufficient number of iterations that the attacker can extract enough information and model the behavior sufficiently to narrow the keyspace down into something feasible to attack. That shouldn't be surprising for anyone who's paid attention to information security for the past couple of decades, since attackers have been using those sorts of techniques for various purposes (such as exploiting TOCTOU vulnerabilities).
Of course, GP systems are not the primary target for this sort of EMF side-channel attack on cryptographic operations anyway. The real profit is attacking embedded systems, such as digital satellite TV boxes, to derive master keys, which can then be used to generate user keys for the black market.
Man, any time anything crypto- or security-related comes up, the Reg Genius Brigade really swings into action.
Biting the hand that feeds IT
