Longer communication for ultra high security, such as banking networks, now possible

TOKYO--November 14, 2002-- 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.
This experiment, which used a 1550nm wavelength optical fiber (a wavelength deemed suitable for long distance telecom communications) has great significance toward the realization of a practical integrated cryptosystem with absolute-security quantum and high-speed, modern cryptography.

*quantum cryptography:
	In the microscopic world, once a system is observed, it is inevitably affected and changes into another state (Heisenberg's Uncertainty Principle). By incorporating the fact that weak light behaves as "photons" subject to this law, quantum cryptography is an unbreakable cryptography with the photons becoming the information carriers.

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.

Main Features

1. High-performance single photon detector for telecom wavelengths
	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.
2.	Practical integrated cryptosystem with 100% guaranteed unbreakable "quantum cryptography" and high-speed "modern cryptography"
	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

1.	Successful quantum cryptosystem implementation at world's longest distance
	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).
2.	A practical cryptosystem with both high security and high speed
	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

1.	Quantum cryptosystem for telecom wavelength (1550nm)
	Basic features:
	-	Key distribution
	-	Eavesdropper detection
	-	Error correcting, privacy amplification
	Specifications:
	-	Bit rate: 7.2 bps
	-	Quantum bit error rate: 7.6 %
	-	Transmission distance: 87 km (optical fiber)
	-	Optics which can compensate for phase and polarization fluctuations
2.	Integrated cryptosystem with conventional cryptography
	Basic features:
	-	One picks up algorithms for his usage (ultimate security/fast encryption)
	-	One Time Pad
	-	Modern cryptography (64bit block cipher MISTY, 128bit block cipher Camellia)

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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 Robert.Barz@hq.melco.co.jp