Cryptography Reference
In-Depth Information
Table 4.1
Assessment of “Classic” Quantum Cryptography
Important Goals for a
Cryptographic Key
Distribution System
QKD Strengths and Weaknesses
Protection of Keys
QKD offers significant advantages in this regard and
indeed this is the main reason for interest in QKD.
Assuming that QKD techniques are properly
embedded into an overall secure system, they can
provide automatic distribution of keys that may
offer security superior to that of competitors.
Authentication
QKD does not in itself provide authentication.
Current strategies for authentication in QKD
systems include prepositioning of secret keys at
the distant device, to be used in hash-based
authentication schemes, or hybrid QKD-public key
techniques.
Robustness
This critical property has not traditionally been taken
into account by the QKD community. Since keying
material is essential for secure communications, it
is extremely important that the flow of keying
material not be disrupted, whether by accident or
by the deliberate acts of an adversary (i.e., by
denial of service). Here QKD has provided a highly
fragile service to date, since QKD techniques have
implicitly been employed along a single point-to-
point link.
Distance- and Location-
Independence
This feature is notably lacking in QKD, which
requires the two entities to have a direct and
unencumbered path for photons between them,
and which can only operate for a few tens of
kilometers through fiber.
Resistance to Traffic Analysis
QKD in general has had a rather weak approach, since
most setups have assumed dedicated,
point-to-point QKD links between communicating
entities, which has thus clearly laid out a map of
the underlying key distribution relationships.
interferometer. Bob contains another modulator and photon detectors, spe-
cifically a twin Mach-Zehnder interferometer and cooled InGaAs APDs.
Here the channel between Alice and Bob is a standard telecommunications
fiber.
In the network context, this system can be viewed as a single, isolated
QKD “link” that allows Alice and Bob to agree upon shared cryptographic
key material. In our terminology, both Alice and Bob are QKD endpoints,
as are other cryptographic stations based on QKD technology, e.g., the Alice
