There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indicates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physical secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnson-noise and a Kirchhoff-loop—i.e., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol—for secure key distribution leads to information theoretic security levels superior to those of today's quantum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer-reviewed publications. The KLJN system is briefly surveyed with discussions about the essential questions such as: perfect and imperfect security characteristics of the key distribution, and how can these two types of securities be unconditional (or information theoretical)?
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[v1] 2012-10-29 10:10:40
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