Susanna Orlic

3D bit-oriented optical storage in photopolymers

The bit-oriented data storage of conventional optical disks may be expanded into the third dimension by using microscopic reflection gratings instead of pits. Microgratings are holographically induced in a photopolymer layer. The Bragg selectivity of holographic volume gratings makes the application of multiplexing methods possible. High storage density may be achieved by combining wavelength multiplexing and multilayer storage. Wavelength multiplexing is realized by recording several gratings overlapping with write beams of different wavelengths. All gratings are recorded simultaneously in the same volume element. By translating a photopolymer sample perpendicularly to the laser beam axis during exposure, stripe-shaped microgratings are induced dynamically with constant linear velocity. The length of a grating is defined by the exposure time. Stripe-shaped gratings are required to realize an areal structure of recorded data similar to the pit-land structure of conventional disks that allows us to overtake the progress made in proceeding CD/DVD technology. Experimental results have been obtained for writing and reading of microholograms in different photopolymer materials including DuPont holographic recording films and CROP photopolymers from Polaroid.

Simple Photonic Emission Analysis of AES

This work presents a novel low-cost optoelectronic setup for time- and spatially resolved analysis of photonic emissions and a corresponding methodology, Simple Photonic Emission Analysis (SPEA). Observing the backside of ICs, the system captures extremly weak photoemissions from switching transistors and relates them to program running in the chip. SPEA utilizes both spatial and temporal information about these emissions to perform side channel analysis of ICs. We successfully performed SPEA of a proof-of-concept AES implementation and were able to recover the full AES secret key by monitoring accesses to the S-Box. This attack directly exploits the side channel leakage of a single transistor and requires no additional data processing. The system costs and the necessary time for an attack are comparable to power analysis techniques. The presented approach significantly reduces the amount of effort required to perform attacks based on photonic emission analysis and allows AES key recovery in a relevant amount of time.

Simple photonic emission analysis of AES: photonic side channel analysis for the rest of us

This work presents a novel low-cost optoelectronic setup for time- and spatially resolved analysis of photonic emissions and a corresponding methodology, Simple Photonic Emission Analysis (SPEA). Observing the backside of ICs, the system captures extremly weak photoemissions from switching transistors and relates them to program running in the chip. SPEA utilizes both spatial and temporal information about these emissions to perform side channel analysis of ICs. We successfully performed SPEA of a proof-of-concept AES implementation and were able to recover the full AES secret key by monitoring accesses to the S-Box. This attack directly exploits the side channel leakage of a single transistor and requires no additional data processing. The system costs and the necessary time for an attack are comparable to power analysis techniques. The presented approach significantly reduces the amount of effort required to perform attacks based on photonic emission analysis and allows AES key recovery in a relevant amount of time.

Modeling of multilayer microholographic data storage

We focus on the investigation of multilayer recording in microholographic data storage. We have developed a numerical model for calculating the electromagnetic scattering from thick microholographic gratings using the Born approximation and the direct volume integral. The signal-to-noise ratio and bit error rate were calculated to estimate the noise arising from interlayer and interhologram cross talk. Measurements were done to prove the validity of the model. The results of our calculations and the measurements show good agreement. We present the application of the model to the investigation of confocal filtering at the image plane and to the evaluation of positioning and wavelength tolerances.

Functional integrated circuit analysis

This work introduces a novel, automated methodology for performing functional analysis of integrated circuits (ICs), such as microcontrollers and smart cards. By selectively executing code on a given chip, the resulting optical emission images yield critical information about the chips functional layout. Automation of the code-generation allows us to generate and process hundreds of test cases that access specific elements of the IC. Subsequently, by correlating the executed code with the images, we are able to locate and identify functional elements of the chips design, such as memory layout and important registers. This methodology provides an efficient way to isolate potential points of interest and thus significantly reduces the amount of effort required to mount attacks. We present exemplary results for a common microcontroller.

Simple photonic emission analysis of AES

This work presents a novel low-cost optoelectronic setup for time- and spatially resolved analysis of photonic emissions and a corresponding methodology, Simple Photonic Emission Analysis (SPEA). Observing the backside of ICs, the system captures extremly weak photo-emissions from switching transistors and relates them to code running in the chip. SPEA utilizes both spatial and temporal information about these emissions to perform side channel analysis of ICs. We successfully performed SPEA of a proof-of-concept AES implementation and were able to recover the full AES secret key by monitoring accesses to the S-Box. This attack directly exploits the side channel leakage of a single transistor and requires no additional data processing. The system costs and the necessary time for an attack are comparable to power analysis techniques. The presented approach significantly reduces the amount of effort required to perform attacks based on photonic emission analysis and allows AES key recovery in a relevant amount of time. We present practical results for the AVR ATMega328P and the AVR XMega128A1.

Holographic reflection gratings in azobenzene polymers.

Writing and reading of reflection gratings in films of an azo side-group polymer are reported. The gratings were induced holographically by use of an argon-ion laser at 488 nm. The measured diffraction efficiency was in the range 2-10%. To estimate the scattering of the reflected light within the material, we further characterized the gratings by calculating a characteristic transmission. A distinct minimum for this transmission was observed, which was redshifted farther from the writing wavelength for gratings written in 50-microm polymer samples.

High-density disc storage by multiplexed microholograms

The new concept of microholographic data storage allows storage capacities of up to 100 GB on a DVD-sized disc 11/. This concept involves bitwise information storage similar to CD and DVD systems. Instead of using pits, the information is coded in form of holographically recorded, microscopic Bragg-reflectors, located in a thin, photosensitive layer (Fig. 1). Each microholographic Bragg-reflector represents one bit, presuming no coding scheme is applied. Microholograms can be stored overlapping in the same volume by using angle multiplexing, wavelength multiplexing or the combination of both. Such storage of multiple information bits in one single position on the disc increases the storage capacity as well as the data transfer rates by the multiplex factor. In contrast to previous holographic storage systems, the storage media are made of cheap and mass-produceable photopolymer layers instead of expensive crystals. Furthermore, the microholographic storage method can be downward compatible with todays Compact-Disk (CD)- and Digital-Versatile-Disk (DVD) systems.

Optical investigation of photopolymer systems for microholographic storage

We investigate different classes of organic photosensitive materials in order to optimize the interaction between the material itself and a surrounding optoelectronic system. The focus of investigation is the application to microholographic data storage. Key issues are the dynamic material response, spatial resolution and photoresponse, spectral and temporal grating development, influence of the light intensity distribution, and impact of pre-exposure. The materials under investigation are cationic ring opening and free radical polymerization systems.

Modeling material saturation effects in microholographic recording

Microholographic data storage system model is presented that includes non-linear and non-local behavior of the storage material for accurate simulation of the system and optimization of the writing process. For the description of the photopolymer material a diffusion based nonlocal material model is used. The diffusion equation is solved numerically and the modulation of the dielectric constant is calculated. Diffraction efficiency of simulated microholograms and measurements were compared, and they show good agreement.