Optical and Digital Techniques for Information Security

Ting‐Chung Poon, Tae-Geun Kim, Kyu B. Doh

We propose a method for secure wireless transmission of encrypted information. By use of an encryption key, an image or document is optically encrypted by optical heterodyne scanning and hence encryption is performed on the fly. We call this technique optical scanning cryptography. The output of the heterodyne encrypted signal is at radio frequency and can be directly sent through an antenna to a secure site for digital storage to be prepared for decryption. In the secure site, an identical optical scanning system to that used for encryption is used, together with a decryption key, to generate an electrical signal. The electrical signal is then processed and sent to a computer to be used for decryption. Utilizing the stored information received from the encryption stage and the electrical information from the secure site, a digital decryption unit performs a decryption algorithm. If the encryption key and the decryption key are matched, the decryption unit will decrypt the image or document faithfully. The overall cryptosystem can perform the incoherent optical processing counterpart of the well-known coherent double-random phase-encoding technique. We present computer simulations of the idea.

Hongtao Wang, Haoran Zhang, Xiaoyan Zhou +8 more

Patrick J. Clarke, Robert John Collins, Vedran Dunjko +3 more

Digital signatures are frequently used in data transfer to prevent impersonation, repudiation and message tampering. Currently used classical digital signature schemes rely on public key encryption techniques, where the complexity of so-called ‘one-way’ mathematical functions is used to provide security over sufficiently long timescales. No mathematical proofs are known for the long-term security of such techniques. Quantum digital signatures offer a means of sending a message, which cannot be forged or repudiated, with security verified by information-theoretical limits and quantum mechanics. Here we demonstrate an experimental system, which distributes quantum signatures from one sender to two receivers and enables message sending ensured against forging and repudiation. Additionally, we analyse the security of the system in some typical scenarios. Our system is based on the interference of phase-encoded coherent states of light and our implementation utilizes polarization-maintaining optical fibre and photons with a wavelength of 850 nm. Quantum digital signatures exploit quantum mechanics to provide verification of messages at the limits of information theory. Clarkeet al.demonstrate a photonic system that provides quantum digital signatures for messages sent to two receivers and is secure against forgery and repudiation.

吴克难 Wu Kenan, 胡家升 Hu Jiasheng, 乌旭 Wu Xu

Naveen Kumar Nishchal

Sudheesh K. Rajput, Dhirendra Kumar, Naveen Kumar Nishchal

We propose an image encryption system based on phase mask multiplexing and photon counting imaging (PCI) technique for multiple image authentications and digital hologram security. Multiple images to be authenticated are converted into phase-only images using a phase-retrieval algorithm in fractional Fourier transform domain. The multiple phase-only images are multiplexed into a single phase-only mask and it is further encrypted into a complex-valued function. The photon-limited image is generated by applying the PCI technique to a complex-valued function. For decryption, the photon-limited decrypted images are obtained after applying the appropriate keys. The photon-limited decrypted image contains sufficient information for verification because this image has sparse representation. To verify the photon-limited decrypted image, the optical correlation filters can be used. The proposed system has also been used for hologram security. For hologram security, the system provides multiple layers of security by hiding multiple encrypted images. The computer simulation results have been presented. The authentication scheme has been tested for securing three-dimensional information through experimentally recorded Fresnel digital hologram.