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Background
and Abstract
 Security of nearly
all modern cryptography is evaluated on a computational complexity basis.
Cryptanalysis requires extraordinary complexity or time. Therefore, it
is pointed out that modern cryptography may be breakable (threatened)
by the advent of high-performance computers such as quantum computers.
On the other hand, quantum cryptography, which has the advantage of being
able to detect eavesdropping on communication channels, is expected to
be realized as an "absolutely unbreakable cryptography" compared
to modern cryptography.
Until now, various long communication experiments for up to tens of kilometers
have been carried out throughout the world. However, to reach success
in telecom wavelength quantum cryptosystems suitable for long-distance
communication, there are several difficulties to be overcome, such as
poor efficiency levels for the single-photon detector for wavelengths
of 1300nm and 1550nm.
Mitsubishi Electric has already successfully demonstrated a quantum cryptosystem
for short wavelength (Mitsubishi Electric News Release--September 26,
2000) and has been striving to develop a quantum cryptosystem for longer-communication
as a total security system.
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Main Features
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High-performance single photon
detector for telecom wavelengths : |
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We have developed a 1550nm single photon detector
with high detection efficiency and low dark count probability.
*dark count probability:
A count in which the detector counts up in case no photons come in. |
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| 2. |
Practical integrated cryptosystem
with 100% guaranteed unbreakable "quantum cryptography"
and high-speed "modern cryptography" : |
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We have developed a practical "integrated quantum
cryptosystem". This modern cryptosystem performs high-speed encryption
of communication data bulk with "encryption keys" which
can be shared by quantum cryptosystems with absolute security. |
Results & Specifications
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Successful quantum cryptosystem
implementation at world's longest distance : |
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We have developed and optimized a quantum cryptosystem
with our single photon detector. As a result, we successfully proved
a quantum cryptosystem over 87km (longest distance in the world). |
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| 2. |
A practical cryptosystem with
both high security and high speed : |
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In conventional cryptographic communications, both
the sender and receiver share the same key, which is used in the encryption
and decryption processes. In our experiment, we realized cryptographic
communications with both high security and high speed by sending "encryption
keys" through the quantum cryptography. |
This work was supported by the project "Research and Development on Quantum
Cryptography" of the Telecommunications Advancement Organization as part
of the Ministry of Public Management, Home Affairs, Posts and Telecommunications
of Japan's program "Research and Development on Quantum Communication Technology".
Future Developments
Our quantum cryptographic technique is applicable
to those communication systems with ultra-high security, such as banking,
foreign policy, defense networks and so on. We attempted to enhance the
performance of the single photon detector and system bit rate and to develop
an user-friendlier integrated cryptosystem. Mitsubishi Electric Corporation
will also apply our quantum cryptosystem to the installed fibers for general
telecommunication use and make the system more compact and attractive as
a commercial product.
Details of Results & Specifications
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| 1. |
Quantum cryptosystem
for telecom wavelength (1550nm) |
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Basic features : |
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Key distribution |
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Eavesdropper detection |
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Error correcting, privacy amplification |
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Specifications
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Bit rate: 7.2 bps |
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Quantum bit error rate: 7.6 % |
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Transmission distance: 87 km (optical fiber) |
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Optics which can compensate for phase and polarization
fluctuations |
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| 2. |
Integrated cryptosystem
with conventional cryptography |
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Basic features
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One picks up algorithms for his usage (ultimate security/fast
encryption) |
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One Time Pad |
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Modern cryptography
(64bit block cipher MISTY, 128bit block cipher Camellia) |
About Mitsubishi Electric
With over 80 years of experience in providing
reliable, high-quality products to both corporate clients and general consumers
all over the world, Mitsubishi Electric Corporation (FTSE: 6503q.l) is a
recognized world leader in the manufacture, marketing and sales of electrical
and electronic equipment used in information processing and communications,
space development and satellite communications, consumer electronics, industrial
technology, energy, transportation and building equipment. The company has
operations in 35 countries and recorded consolidated group sales of 3,649
billion yen (US$27.4 billion) in the year ended March 31, 2002. For more
information about Mitsubishi Electric, visit Global.MitsubishiElectric.com.
For more information:
(Media inquiries only)
Public Relations Department
Mitsubishi Electric Corporation
Tel: +81-3-3218-2346
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-- Mitsubishi Electric Corporation (President and CEO:
Tamotsu Nomakuchi) announced the successful results of
their experimental quantum cryptosystem over 87km (approximately
54 miles), the longest in world, in their report titled
"Quantum Cryptosystem over the distance of 87km with
Absolute Security Against Cryptanalysis". This distance
is roughly the same distance of that between Tokyo and
Mt. Fuji.
