Cryptographic hash functions and CD-based optical biosensors

Cameron L.Jones

Centre for Mathematical Modelling and the Environmnent & Biotechnology Centre

Faculty of Engineering and Industrial Sciences & Faculty of Life and Social Sciences

Swinburne University of Technology, Hawthorn, Victoria, 3122, Australia

cajones@swin.edu.au

 

There has been considerable recent interest in the use of compact disc technology for biological sensor development and for rapid test miniaturisation.љ These methods take advantage of the nanomicroscopic scale of digital data in consumer-grade optical discs; as well as the plasmon resonance effect at the dielectric metal interface.љ Allied work in photonics has shown that light transmission across nanoholes can give rise to quantum effects without complicated apparatus.љ A fundamental technique in microbiology is the differential Gram stain into positive (blue) and negative (red) populations. How the cell wall resists decolourisation is useful in primary identification and taxonomic classification.љ Historically, a microscope is used to distinguish between the two colours.љ This paper develops and empirically tests an automated method to perform the differential Gram stain using cells immobilised on the data surface of CD-R.љ Notably, the method does not require a light microscope for test scoring.љ The staining procedure begins with fixing cells to the data surface of a recordable compact disc, prerecorded with well-defined audio, like pink noise or the digit series .љ We exploit the fact that lasers in CD-ROM, CD-RW, DVD-R and DVD-RW read digital information at fixed wavelength at a resolution between ~ 635-780nm.љ Because CD's generate surface plasmons at the data surface, this effect creates localized regions that admit quantum entanglement of photons, and together with rotational effects, photon transmission is modelled as a nonlinear process across cellular nanoholes.љ Surface plasmons and the induced error correction during chaotic photon fan-out are exploited to develop a set of statistical testing procedures that are useful in cell classification based on the Gram-stain, using consumer-grade hardware.љ The method was tested against the following prokaryotes, Gram negative (red): Escherichia coli and Serratia marcesens and the Gram positive (blue): Bacillus subtilus, Bacillus cereus and Staphylococcus epidermidis.љ Differential staining of the larger eukaryote, Saccharomyces cerevisiae on CD-R was also successful.љ A general equation was developed to measure the photon scattering effect caused by light transmission through the cell morphology by correlating measures of error correction, time delay, drive performance and mean values for fifteen different hashing and message digest functions.љ The use of hash functions to evaluate cell shape, colour, size and spatial distribution is thought to be due to the fact that these algorithms are sensitive to internal numeric collisions.љ The combination of light transmission under rotation across a rough surface and hash algorithm instability can be exploited to return convergent digital signatures for biological samples that can be used in hexadecimal, octal or decimal expansion.љ We briefly comment on the potential of this chaotic method for 'nanocipher' key generation, and how combining cells and software algorithms on CD-based digital data, offers new challenges in the development of hybrid encryption protocols and pseudo-random bit generators.љ Differential staining of cells on CD is rapid, flexible and can be adapted for other cell lines or human-specimens.љ The method is reproducible, but requires calibration for the user's individual hardware system.љ Calibrating the system for colour classification was simple to perform by printing shapes in different colours direct onto the CD data surface using a Casio Thermal Disc Title Printer.љ The principal conclusion was that cells that exhibit the strongest staining reaction, in this case, E. coli and S. epidermidis could be easily classified as either red or blue using one or more of the measured variables; while cells that exhibit low levels of staining, like S. marcesens are more difficult to interpret.љ As well, directly examining the number of C2 errors during disc surface scanning can also be used like spectroscopic traces to index local and global scaling properties of cell density distribution.