Encryption Applications Research Articles

Room-Temperature Persistent Phosphorescence of Aggregated Gold Nanoclusters under Molecular Crystal Confinements.

We report color-tunable and solvent-processable persistent fluorescence to phosphorescence switching at room temperature by doping gold nanoclusters (AuNCs) inside molecular crystals. This provides a significant insight into the tunability of the photoluminescence property of the dopant depending on the crystal environment and compactness of confinement, with the possibility of energy transfer from crystal to aggregated AuNCs. For test cases, we have doped histidine-stabilized AuNCs (HIS-AuNCs) inside histidine (HIS-AuNCs-HIS) and isophthalic acid (HIS-AuNCs-IPA) crystals, respectively, and glutathione-stabilized AuNCs (GSH-AuNCs) inside histidine crystals (GSH-AuNCs-HIS). The maximal phosphorescence decay time recorded for crystal doped aggregated AuNCs was 9.38 ms, and the photoluminescence quantum yield value was measured as 25%. The possible energy states and potential interactions between aggregated NCs and host crystals were accounted for through density functional theory calculations and docking techniques, respectively. This finding opens new possibilities for designing and producing color-tunable persistent AuNC-based luminous crystals for multilayer information encryption, display, and biological applications.

High-Stability Near-Infrared Luminescent Glass Ceramic and Its Applications.

Near-infrared (NIR) light, valuable for its biological penetration and invisibility to the human eye, is a crucial tool in biomedicine, environmental monitoring, anticounterfeiting, and information encryption, yet traditional NIR luminescent materials are often unstable in humid conditions. Here, a highly stable MgGeO3:Mn2+ glass ceramic (GC) with NIR luminescence was successfully synthesized. As-obtained GC700 boasts exceptional luminescent capabilities and possesses abundant trap structures, enabling data inscription with a 405 nm laser and retrieval via laser/thermal excitation. Moreover, the emission peak of Mn2+ can be manipulated from 630 to 691 nm by increasing the annealing treatment temperature. With the harnessing of the effective NIR emission, stable carrier characteristics, and numerous trap structures, there is potential for application in information encryption. Accordingly, we explored the application of MgGeO3:Mn2+ GC (GC700 and GC800) samples in precious three-dimensional (3D) information storage and NIR mechanoluminescence (ML) for biological tissue imaging. These applications demonstrate the potential and versatility of electron-capturing NIR luminescent materials in a range of cutting-edge fields.

Simultaneous Dynamic Display of Meta‐Hologram and Meta‐Nanoprinting with High Frame Rate

AbstractDynamic holography can reconstruct realistic and highly interactive 3D scenes, offering a promising way for future display. Emerging metasurface with small pixel size and powerful light modulation capability demonstrates performance superior to traditional spatial light modulators, but dynamic meta‐holography with high information capacity and high frame rate remains a challenge. This paper presents a design scheme combining a preset polarization‐dependent metasurface with a high‐speed projection module to realize smooth dynamic display at multiple polarization states. With the projection module, the system can achieve dynamic meta‐holography at two orthogonal circular polarization states with 237 and 247 different holographic frames respectively, and grayscale meta‐nanoprinting at a linear polarization state with three different patterns. At the same time, the polarization multiplexed dynamic display scheme enables independent displays at three distinct polarization states with an extremely high frame rate (9523 frames per second). This advancement holds promise for applications in dynamic holographic display, optical encryption, virtual reality, and information storage.

Retraction Note: Construction of S-box based on chaotic Boolean functions and its application in image encryption

Retraction Note: Construction of S-box based on chaotic Boolean functions and its application in image encryption

Thermal-treatment controlled room temperature phosphorescence of carbon dots for anti- counterfeiting

Due to the high stability, hypotoxicity and tunable optical properties, room temperature phosphorescence (RTP) carbon dots (CDs) have a great range of application in anti-counterfeiting encryption, bioimaging and optoelectronic devices, etc. Nevertheless, the synthesis procedures for RTP CDs are always pricey, burdensome and involve toxic chemicals. Herein, a facile method to produce RTP CDs materials by heat treatment of creatine and boric acid (BA) at 350 °C is reported. TEM, XRD, FT-IR and XPS are carried out and the structural characterizations showed that B–C covalent bond and CDs embedded in the rigid B2O3 matrix stabilize the triplet excitons and limit the nonradiative transition. The yellow green RTP CDs/BA displayed an ultralong lifetime of 1.286 s and last more than 5 s to naked eye. What's more, the prepared CDs/BA are successfully applied in anti-counterfeiting and information encryption. This work provides new insights to design metal-free RTP CDs with persistent luminescence for promising remarkable applications.

Sulfur-doped carbon dots and g-C3N4 composite with thermally activated delayed fluorescence for white-light illumination and anticounterfeiting

Long-lived afterglow materials have attracted considerable interest in the fields of information security and illumination. Herein, a novel carbon dot (CD)-based thermally activated delayed fluorescence (TADF) material was synthesized by embedding sulfur-doped CDs (SCDs) into a graphitic carbon nitride matrix. The formation of covalent bonds between the matrix and SCDs enhances the stabilization of the triplet state in the composite, effectively suppressing nonradiative transitions. This stabilization, coupled with the effects of sulfur doping and covalent bonding, reduces the singlet–triplet splitting energy in the composite, thereby facilitating reverse intersystem crossing and resulting in TADF emission. This composite material has been successfully employed in the development of three types of CD-based white light–emitting diodes (WLEDs) excited by blue light. These WLEDs exhibit color temperatures of 7641, 5590, and 3215 K, with CIE coordinates of (0.30, 0.29), (0.33, 0.30), and (0.42, 0.40), respectively. The corresponding values of the color rendering index are recorded as 81.86, 90.13, and 75.07. In addition, this research provides a brief demonstration of the potential of the composite in information encryption and visible-light encryption applications. Furthermore, this study contributes to the advancement of CD utilization in the WLED field, promoting the development of next-generation CD-based WLEDs with exceptional properties.

A novel S-box generator using Frobenius automorphism and its applications in image encryption

A novel S-box generator using Frobenius automorphism and its applications in image encryption

High Resolution Nanostructuring of Perovskites With Tunable Morphologies by Ultrafast Laser Direct Writing

AbstractMetal halide perovskites (MHPs) have attracted increasing attention in various optoelectronic devices due to their exceptional optical and electrical properties. The high precision patterning of MHPs is crucial adjective for device fabrication, while it is severely hindered by the active and sensitive chemistry of MHPs. In this work, high resolution and tunable nanostructuring of 2D MHP films are achieved by ultrafast laser direct writing (ULDW). The feature size of the created structure is down to 47 nm (λ/21), which is far beyond the diffraction limit of the optical system. The study proves the critical influence of the thermodynamic properties of materials on structure morphologies and establish a new mechanism of molten phase self‐evolution (MPSE) for the formation of super‐solution convex structures, which provides a new understanding for ultrafast laser‐matter interaction and high‐resolution patterning with ULDW. Different structure morphologies bring tunable optical properties. The applications are demonstrated in multimode information storage and encryption. The findings open new approaches to achieve hyperfine multi‐morphological structures on MHPs, which can boost many MHPs integration applications in nanophotonics, on‐chip electronics, and information encryption.

Michelson Interferometric Methods for Full Optical Complex Convolution.

Optical real-time data processing is advancing fields like tensor algebra acceleration, cryptography, and digital holography. This technology offers advantages such as reduced complexity through optical fast Fourier transform and passive dot-product multiplication. In this study, the proposed Reconfigurable Complex Convolution Module (RCCM) is capable of independently modulating both phase and amplitude over two million pixels. This research is relevant for applications in optical computing, hardware acceleration, encryption, and machine learning, where precise signal modulation is crucial. We demonstrate simultaneous amplitude and phase modulation of an optical two-dimensional signal in a thin lens's Fourier plane. Utilizing two spatial light modulators (SLMs) in a Michelson interferometer placed in the focal plane of two Fourier lenses, our system enables full modulation in a 4F system's Fourier domain. This setup addresses challenges like SLMs' non-linear inter-pixel crosstalk and variable modulation efficiency. The integration of these technologies in the RCCM contributes to the advancement of optical computing and related fields.

S-Boxes design based on the Lu-Chen system and their application in image encryption

S-Boxes design based on the Lu-Chen system and their application in image encryption

Dual-band complex-amplitude metasurface empowered high security cryptography with ultra-massive encodable patterns

Abstract The significance of a cryptograph method lies in its ability to provide high fidelity, high security, and large capacity. The emergence of metasurface-empowered cryptography offers a promising alternative due to its unparalleled wavefront modulation capabilities and easy integration with traditional schemes. However, the majority of reported strategies suffer from limited capacity as a result of restricted independent information channels. In this study, we present a novel method of cryptography that utilizes a dual-band complex-amplitude meta-hologram. The method allows for the encoding of 225 different patterns by combining a modified visual secret-sharing scheme (VSS) and a one-time-pad private key. The use of complex-amplitude modulation and the modified VSS enhances the quality and fidelity of the decrypted results. Moreover, the transmission of the private key through a separate mechanism can greatly heighten the security, and different patterns can be generated simply by altering the private key. To demonstrate the feasibility of our approach, we design, fabricate, and characterize a meta-hologram prototype. The measured results are in good agreement with the numerical ones and the design objectives. Our proposed strategy offers high security, ultra-capacity, and high fidelity, making it highly promising for applications in information encryption and anti-counterfeiting.

Programmable Optical Encryption Based on Electrical-Field-Controlled Exciton-Trion Transitions in Monolayer WS2.

Optical encryption is receiving much attention with the rapid growth of information technology. Conventional optical encryption usually relies on specific configurations, such as metasurface-based holograms and structure colors, not meeting the requirements of increasing dynamic and programmable encryption. Here, we report a programmable optical encryption approach using WS2/SiO2/Au metal-oxide-semiconductor (MOS) devices, which is based on the electrical-field-controlled exciton-trion transitions in monolayer WS2. The modulation depth of the MOS device reflection amplitude up to 25% related to the excitons ensures the fidelity of information, and the decryption based on the near excitonic resonance assures security. With such devices, we successfully demonstrate their applications in real-time encryption of ASCII codes and visual images. For the latter, it can be implemented at the pixel level. The strategy shows significant potential for low-cost, low-energy-consumption, easily integrated, and high-security programmable optical encryptions.

Dimension-Controlled VO2 Film for Optoelectronic Logic Gates and Information Encryption.

As the fields of photonics and information technology develop, a lot of novel applications based on VO2 material, such as optoelectronic computing and information encryption, have been developed. While the performance of these devices was not only closely associated with the VO2 phase transition properties but also depended on their dimensional characteristics. In the current study, we conducted the dimension-controlled vanadium dioxide (VO2) film growth, resulting in the epitaxial 2-dimensional (2D) VO2 film and well-distributed 3-dimensional (3D) VO2 crystal film deposition, respectively. It was revealed that, unlike the 2D film, the pronounced localized surface plasmon resonance dominated the near-infrared spectrum across the phase transition for the 3D VO2 film due to the naturally formed meta-surface structure, which showed a transmittance valley in the infrared spectrum after metallization. Based on this distinct infrared spectrum feature in the 3D VO2 film, we proposed an optoelectronic logic gate controlled by the input voltage and the probing Vis/IR light. By detecting the transmittance states of the probing light with different wavelengths, we achieved multistate encoding functions and demonstrated the information encryption application. This new conception device also showed great potential for some other applications such as optoelectronic coupled computing, information encryption, and optical near-field sensing computing.

Room temperature phosphorescence materials based on small organic molecules: Design strategies and applications

AbstractRoom‐temperature phosphorescence (RTP) materials have attracted significant attention due to their applications in various fields such as information storage and encryption, organic light‐emitting diode (OLED), sensing, lighting and display, biological imaging, and photodynamic therapy. Traditionally, RTP materials can be efficiently developed using inorganic systems with noble metals or rare earth elements. Recently, many efforts have been devoted to the development of RTP materials based on small organic molecules. The strategies to construct RTP materials include hydrogen bonding, heavy atom effect, n–π* transitions, π–π stacking, donor–acceptor effect, and host–guest doping. Herein, we summarize the recent examples of RTP materials based on small organic molecules primarily focusing on their design strategies and properties. Moreover, their promising applications in information encryption, OLED, as well as bio‐imaging and phototherapy are discussed. The challenges and perspectives are given to provide inspiration toward the future development of organic RTP materials.

Autonomous three-dimensional oscillator with two and four wings attractors embedded in the microcontroller: analysis, amplitude controls, random number generator, and image encryption application

Robust chaotic systems offer unpredictability, complex dynamics, noise-like properties, efficient bifurcation behavior, and the ability to model real-world phenomena, making them valuable in diverse scientific and engineering applications. This paper details on the dynamical appraisal, amplitude controls, microcontroller execution, Random number generator (RNG) of an autonomous three-dimensional (3D) oscillator with two and four wings attractors (ATDOTFWA), and its image encryption application. Thanks to the Routh-Hurwitz criteria, five steady states found in the ATDOTFWA are classified as stable or unstable, depending on its two control parameters. During the numerical simulations employing the Runge–Kutta scheme, the ATDOTFWA exhibit a wide range of dynamic behaviors, including no oscillations, Hopf bifurcation, limit cycle, five distinct presentations of two wings chaotic structures, monostable and bistable two wings chaotic structures, bistable and monostable regular oscillations, chaotic bursting characteristics, coexistence of period-2-oscillations and four wings chaotic structure, and four wings chaotic attractor which were validated experimentally by the microcontroller implementation. The total and partial controls of the amplitude are achieved in the ATDOTFWA. A RNG is designed based on the ATDOTFWA, and the generated random numbers are successfully tested using the ENT and NIST 800–22 statistical test suites, demonstrating the reliability of the ATDOTFWA-based RNG. This reliability is further confirmed through the application of the ATDOTFWA-based RNG in an efficient and secure image encryption process, where the generated random numbers are used as the encryption key. The effectiveness of the image encryption process is validated through comprehensive cryptanalysis, with an encryption time of 0.1923 s for a 512×512 image, an average normalized pixel change rate (NPCR) of 99.6126%, an average unified average changing intensity (UACI) of 33.4578%, and an average information entropy of 7.9994.

Retraction Note: A novel construction of substitution box for image encryption applications with Gingerbreadman chaotic map and S8 permutation

Retraction Note: A novel construction of substitution box for image encryption applications with Gingerbreadman chaotic map and S8 permutation

Unexpected tunable photoluminescence and emission mechanism during the gradual increase of cyclic glucose units

Excitation-dependent (λex-dependent) emission is one of the most common emission characteristics of nonconventional luminophores. Previously, we have reported D-xylose crystals has an obvious λex-dependent color tunable persistent room temperature phosphorescence (p-RTP) from blue to green, but its p-RTP emission at long wavelength is very weak. To further explore this attractive multicolor p-RTP behavior, and to enhance its tunability, the photoluminescence (PL) behavior of three common cyclodextrins (CDs), namely α-CD, β-CD and γ-CD, including solution and single crystals, were studied. Their single crystals demonstrate λex-dependent multicolor p-RTP properties in the order of β-CD>α-CD>γ-CD, rather than the strongest with the least glucose units (α-CD). Among them, the λex-dependent tunable p-RTP of β-CD and α-CD is superior to that of D-(+)-xylose single crystal. The above unexpected phenomena could be explained reasonably through detailed single crystal structure analysis and theoretical calculations. The emission behavior of solution and single crystals of CDs can be reasonably explained by the clustering-triggered emission (CTE) mechanism. Furthermore, CD-based covalent organic frameworks (COF) and supramolecules are readily fabricated, which own significantly enhanced p-RTP emission. Due to the intriguing PL property as well as hydrophilic rim and low biotoxicity of CDs, successful imaging of HCT116 cells and encryption applications were demonstrated. It is believed that the intrinsic PL properties of CDs, especially their regularly adjustable multicolor p-RTP that varies with the number of glucose units, have significant guidance for the development of a series of multicolor luminescent materials.

A new encryption algorithm for image data based on two-way chaotic maps and iterative cellular automata

Due to their simplicity of implementation and compliance with the encryption issue, chaotic models are often utilized in picture encryption applications. Despite having many benefits, this approach still has a crucial space issue that makes encryption algorithms based on it susceptible to brute-force assaults. This research’s proposed novel picture encryption technique has a vast key space and great key sensitivity. To achieve this goal, the proposed method combines two-way chaotic maps and reversible cellular automata (RCA). First, this approach uses a two-way chaotic model named spatiotemporal chaos for image confusion. This step includes permuting the image pixels using a chaotic map at the byte level. Then, the RCA model is utilized for image diffusion. In this step, the RCA model iterates over image pixels to modify them at the bit level. The method’s performance in encrypting grayscale images was evaluated using various analysis methods. According to the results, the proposed method is a compelling image encryption algorithm with high robustness against brute-force, statistical, and differential attacks.

Ultra-adherable dual-network conductive hydrogel with moistening and anti-freezing as a flexible sensor

Multifunctional conductive hydrogels have shown great promise in wearable flexible sensor application. This paper reported a dual-network self-healing electrically hydrogel through simple one-pot polymerization, which initiated from Ag+- lignin nanoparticles (LNPs) -APS redox system. Owing to the reversible metal coordination and hydrogen bonding cross-linked among polymer network, the resulting conductive hydrogel-based sensor demonstrated excellent stretchable, adhesion strength, and fatigue resistance. Additionally, the complex hydrogel (PHEMA/SA/Gly/Ca) incorporating with glycerol and CaCl2 in particular exhibited strong frost resistance (−40oC) and moisturizing qualities to monitor the motion signals in the low-temperature dry state. Therefore, the fabricated wearable sensor is sufficient for detecting large and small human motions, suggesting lots of promising applications in electronic skins, information identification and encryption, and human-motion monitoring.

Control the handedness of CPL using a cholesteric liquid crystal elastomer film

The reversible modulation of the handedness of circularly polarized luminescence (CPL) is highly important for anti-counterfeiting, flexible displays, and encrypted transmission applications. A thermochromic cholesteric liquid crystal (CLC) oligomer was prepared and applied for printing colourful patterns. The structural colours of the patterns were sensitive to the temperature. A CLC elastomer (CLCE) film was prepared using this CLC oligomer, which exhibited mechanochromic property with a wide range of structural colour changes. A CPL-active CLCE film was obtained with the addition of a fluorescent dye. The handedness of the CPL was reversibly switched upon uniaxial stretching of the film. This work not only sheds insight into CPL handedness control based on the CLCE system, but also provides possibilities for flexible decorations and displays.