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Side-Channel-Free Quantum Key Distribution

<01>Both classical and quantum cryptography rely on the (rarely made explicit) assumption that the legitimate users have the use of private spaces which are assumed perfectly inaccessible to an eavesdropper. Yet certainly in classical cryptography many successful attacks rely on tell-tale information that leaks out from or is actively gleaned by probing these so-called private spaces. We construct a protocol in quantum cryptography which forbids probing of the output port of the private space. We rigorously prove its security. Finally, we show how information leakage can be effectively eliminated by blind quantum processing replacing all classical post-processing.