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CHAOS-BASED COMMUNICATIONS
- Coordinator: Prof. David Citrin (Georgia Tech, USA and UMI Georgia Tech-CNRS, France)
- Permanent members: Prof. David Citrin and Dr. Alexandre Locquet (UMI Georgia Tech-CNRS, France and Georgia Tech Lorraine)
- Associate members: Assist. Prof. Marc Sciamanna (Supélec-LMOPS, France and UMI Georgia Tech-CNRS, France)
- PhD students: Damien Rontani (UMI Georgia Tech-CNRS, France, and Supélec-LMOPS, France, and Georgia Tech, USA)
CONTEXT
This project focuses on the use of the chaotic dynamics of semiconductor-based laser systems to serve as the basis for secure optical communications systems. Such systems are of interest to commercial, military, and individual users. To be deployed to greatest possible extent, chaos-based communications systems must be secure, capable of high data rates, and compatible with existing optical-communications infrastructure.
At present, most of the principles used in communications employ linear theory. In particular, great effort is applied in designing conventional transmitters and receivers to make their components operate in a linear regime. Instead of spending this effort attempting to circumvent nonlinearities, we propose to exploit the complicated dynamics naturally produced by nonlinear optical dynamical systems. These complex dynamics, long viewed as something to be avoided, can also be considered a potential source of numerous improvements in communications. Complicated and unpredictable dynamics can be exploited to physically encrypt a message.
- Description of a chaos based communication scheme
- Alice encrypts her data using the chaotic behavior of a laser. Then, the encrypted data is transmitted to Bob, who decrypts it using chaos synchronization. An eavesdropper, Eve, can hack the communication channel and decrypt the encrypted data, if she manages to identify Alice’s laser parameters.
Nonlinear dynamical systems have the potential for greater efficiency, since they react sensitively to small perturbations and can thus be controlled and can produce signals with small amounts of energy. They also have the potential for great information-bearing capacity, since the complex signals and the variety of states produced offers more possibilities for compact conventional encoding of information. Furthermore, since nonlinear optical communications are not restricted to the standard spectra of sinusoidal frequency bands, the number of channels available for communications could be larger than with linear systems and only limited by the ability of receivers to distinguish between different chaotic states.
Optoelectronic cryptosystems can be built using standard semiconductor lasers subjected to optical feedback or to optical injection from other lasers. This further promises the ability to easily construct time-delay optoelectronic cryptosystems operating in various portions of the electromagnetic spectrum. Nonetheless, such systems exhibit rich dynamical behavior. In certain operating regimes, the output of the semiconductor laser can be chaotic. These chaotic dynamics can be used to conceal or encode, at the physical level, an information-bearing signal in real time. In order to decode the signal, a semiconductor-laser-based receiver duplicating the parameters of the transmitter can be synchronized with the transmitter and can be used to extract the information-bearing signal.
RESEARCH OBJECTIVES
I. Security analysis of optical chaotic communication systems
In chaotic regime, the synchronization of a receiver laser depends crucially and sensitively on the emitter laser system internal and operating parameters. An eavesdropper who does not know these parameters is unlikely to be able to decode the signal. Chaotic encryption can thus be considered a physical-level implementation of private-key cryptography, in which the key is the collection of the internal and operating parameters. But contrary to the case of a software implementation of private-key encryption, even if an eavesdropper knew the private key it would be physically difficult for him to build a decoder laser because of the difficulty of fabricating a laser with given internal parameters. There are, however, potential ways to crack the system by a suitable analysis of the output of the transmitter. It is thus necessary to determine ways to build optical chaos-based communication systems resist cracking.
II. Performances enhancement of optical chaotic communication systems
The bandwidth of the communications system is mainly occupied by the chaotic output of the transmitter to enable synchronization with the receiver. This bandwidth may not be available to the information-bearing signal. Thus, chaotic cryptosystems, as deployed, suffer from data-rate or bandwidth limitations. this project aims to determine ways to build optical chaos-based communications that offer a better security level, that attain higher bit rates, that are compatible with current digital communications systems, and that work in different regions of the electromagnetic spectrum. Our ideas will be applied to a test bed based on coupled semiconductor lasers subjected to optical feedback or/and injection.
SOME ACHIEVEMENTS
- Impact of polarization dynamics on the synchronization of vertical-cavity surface-emitting lasers subjected to polarization-preserved and polarization-rotated feedback.
- Identification of the conditions that lead to parameter concealment for a chaotic semiconductor laser subjected to external optical feedback (external-cavity semiconductor laser ECSL).
- Dynamical explanation of the concealment of the parameters of an ECSL
- Novel multiplexing concepts for chaos-based communications leading to an efficient use of the chaotic spectrum.
- Experimental setup of an external cavity semiconductor laser (ECSL)
A FEW PUBLICATIONS:
Delay Identification 2 - 5.5 Mb to be published in JQE |
Delay Identification 1 - 372 kb Optics Letters |
Synchronization of VCSELS-1 modes/2modes - 263.8 kb Optics Letters |
|
Synchronization regimes of VCSELS - 3.8 Mb Phys. Rev. E |
Chaos Digitization - 543.4 kb IEE Proc. Optoelectronics |
Parameter Identification - 1.2 Mb Journal of Optical Technology |
Keywords
cryptography, optics
-->CHAOS-BASED COMMUNICATIONS
- Coordinator: Prof. David Citrin (Georgia Tech, USA and UMI Georgia Tech-CNRS, France)
- Permanent members: Prof. David Citrin and Dr. Alexandre Locquet (UMI Georgia Tech-CNRS, France and Georgia Tech Lorraine)
- Associate members: Assist. Prof. Marc Sciamanna (Supélec-LMOPS, France and UMI Georgia Tech-CNRS, France)
- PhD students: Damien Rontani (UMI Georgia Tech-CNRS, France, and Supélec-LMOPS, France, and Georgia Tech, USA)
CONTEXT
This project focuses on the use of the chaotic dynamics of semiconductor-based laser systems to serve as the basis for secure optical communications systems. Such systems are of interest to commercial, military, and individual users. To be deployed to greatest possible extent, chaos-based communications systems must be secure, capable of high data rates, and compatible with existing optical-communications infrastructure.
At present, most of the principles used in communications employ linear theory. In particular, great effort is applied in designing conventional transmitters and receivers to make their components operate in a linear regime. Instead of spending this effort attempting to circumvent nonlinearities, we propose to exploit the complicated dynamics naturally produced by nonlinear optical dynamical systems. These complex dynamics, long viewed as something to be avoided, can also be considered a potential source of numerous improvements in communications. Complicated and unpredictable dynamics can be exploited to physically encrypt a message.
- Description of a chaos based communication scheme
- Alice encrypts her data using the chaotic behavior of a laser. Then, the encrypted data is transmitted to Bob, who decrypts it using chaos synchronization. An eavesdropper, Eve, can hack the communication channel and decrypt the encrypted data, if she manages to identify Alice’s laser parameters.
Nonlinear dynamical systems have the potential for greater efficiency, since they react sensitively to small perturbations and can thus be controlled and can produce signals with small amounts of energy. They also have the potential for great information-bearing capacity, since the complex signals and the variety of states produced offers more possibilities for compact conventional encoding of information. Furthermore, since nonlinear optical communications are not restricted to the standard spectra of sinusoidal frequency bands, the number of channels available for communications could be larger than with linear systems and only limited by the ability of receivers to distinguish between different chaotic states.
Optoelectronic cryptosystems can be built using standard semiconductor lasers subjected to optical feedback or to optical injection from other lasers. This further promises the ability to easily construct time-delay optoelectronic cryptosystems operating in various portions of the electromagnetic spectrum. Nonetheless, such systems exhibit rich dynamical behavior. In certain operating regimes, the output of the semiconductor laser can be chaotic. These chaotic dynamics can be used to conceal or encode, at the physical level, an information-bearing signal in real time. In order to decode the signal, a semiconductor-laser-based receiver duplicating the parameters of the transmitter can be synchronized with the transmitter and can be used to extract the information-bearing signal.
RESEARCH OBJECTIVES
I. Security analysis of optical chaotic communication systems
In chaotic regime, the synchronization of a receiver laser depends crucially and sensitively on the emitter laser system internal and operating parameters. An eavesdropper who does not know these parameters is unlikely to be able to decode the signal. Chaotic encryption can thus be considered a physical-level implementation of private-key cryptography, in which the key is the collection of the internal and operating parameters. But contrary to the case of a software implementation of private-key encryption, even if an eavesdropper knew the private key it would be physically difficult for him to build a decoder laser because of the difficulty of fabricating a laser with given internal parameters. There are, however, potential ways to crack the system by a suitable analysis of the output of the transmitter. It is thus necessary to determine ways to build optical chaos-based communication systems resist cracking.
II. Performances enhancement of optical chaotic communication systems
The bandwidth of the communications system is mainly occupied by the chaotic output of the transmitter to enable synchronization with the receiver. This bandwidth may not be available to the information-bearing signal. Thus, chaotic cryptosystems, as deployed, suffer from data-rate or bandwidth limitations. this project aims to determine ways to build optical chaos-based communications that offer a better security level, that attain higher bit rates, that are compatible with current digital communications systems, and that work in different regions of the electromagnetic spectrum. Our ideas will be applied to a test bed based on coupled semiconductor lasers subjected to optical feedback or/and injection.
SOME ACHIEVEMENTS
- Impact of polarization dynamics on the synchronization of vertical-cavity surface-emitting lasers subjected to polarization-preserved and polarization-rotated feedback.
- Identification of the conditions that lead to parameter concealment for a chaotic semiconductor laser subjected to external optical feedback (external-cavity semiconductor laser ECSL).
- Dynamical explanation of the concealment of the parameters of an ECSL
- Novel multiplexing concepts for chaos-based communications leading to an efficient use of the chaotic spectrum.
- Experimental setup of an external cavity semiconductor laser (ECSL)
A FEW PUBLICATIONS:
|
Delay Identification 2 - 5.5 Mb to be published in JQE |
Delay Identification 1 - 372 kb Optics Letters |
Synchronization of VCSELS-1 modes/2modes - 263.8 kb Optics Letters |
|
Synchronization regimes of VCSELS - 3.8 Mb Phys. Rev. E |
Chaos Digitization - 543.4 kb IEE Proc. Optoelectronics |
Parameter Identification - 1.2 Mb Journal of Optical Technology |
Keywords
cryptography, optics
