RESUMEN

In this paper, we present a new protocol for achieving lower noise and consequently a higher dynamic range in optical encryption. This protocol allows for the securing and optimal recovery of any arbitrary grayscale images encrypted using an experimental double random phase mask encoding (DPRE) cryptosystem. The protocol takes advantage of recent advances that help reduce the noise due to the correlation of random phase mask in the decryption procedure and introduces the use of a "reference mask" as a reference object used to eliminate the noise due to the complex nature of the masks used in experimental DRPE setups. This noise reduction increases the dynamic range of the decrypted data, retaining the grayscale values to a higher extent and opening new possible applications. We detailed the procedure, and we present the experimental results, including an actual experimental video of a grayscale scene, confirming the validity of our proposal.

RESUMEN

In this contribution, we implement two techniques to reinforce optical encryption, which we restrict in particular to the QR codes, but could be applied in a general encoding situation. To our knowledge, we present the first experimental-positional optical scrambling merged with an optical encryption procedure. The inclusion of an experimental scrambling technique in an optical encryption protocol, in particular dealing with a QR code "container", adds more protection to the encoding proposal. Additionally, a nonlinear normalization technique is applied to reduce the noise over the recovered images besides increasing the security against attacks. The opto-digital techniques employ an interferometric arrangement and a joint transform correlator encrypting architecture. The experimental results demonstrate the capability of the methods to accomplish the task.

RESUMEN

We report, to our knowledge for the first time, the experimental implementation of a quick response (QR) code as a "container" in an optical encryption system. A joint transform correlator architecture in an interferometric configuration is chosen as the experimental scheme. As the implementation is not possible in a single step, a multiplexing procedure to encrypt the QR code of the original information is applied. Once the QR code is correctly decrypted, the speckle noise present in the recovered QR code is eliminated by a simple digital procedure. Finally, the original information is retrieved completely free of any kind of degradation after reading the QR code. Additionally, we propose and implement a new protocol in which the reception of the encrypted QR code and its decryption, the digital block processing, and the reading of the decrypted QR code are performed employing only one device (smartphone, tablet, or computer). The overall method probes to produce an outcome far more attractive to make the adoption of the technique a plausible option. Experimental results are presented to demonstrate the practicality of the proposed security system.

RESUMEN

We introduce for the first time the concept of an information "container" before a standard optical encrypting procedure. The "container" selected is a QR code which offers the main advantage of being tolerant to pollutant speckle noise. Besides, the QR code can be read by smartphones, a massively used device. Additionally, QR code includes another secure step to the encrypting benefits the optical methods provide. The QR is generated by means of worldwide free available software. The concept development probes that speckle noise polluting the outcomes of normal optical encrypting procedures can be avoided, then making more attractive the adoption of these techniques. Actual smartphone collected results are shown to validate our proposal.

RESUMEN

In experimental optodigital encrypting architectures, the use of a reference wave is essential. In this contribution, we present an experimental alternative to avoid the reference wave during the encrypting procedure in a joint transform correlator architecture by introducing the concept of a master key. Besides, the master key represents an additional security element for the entire protocol. In our method, the master key is holographically processed and used during the encryption process with the encrypting key. We give the mathematical description for the process in case of a single input object and then we extend it to multiple input objects. We present the experimental demonstration of the proposed method including two examples where this technique is successfully applied for several input objects.

RESUMEN

We present the first experimental technique to encrypt a movie under a joint transform correlator architecture. We also extend the method to multiplex several movies in a single package. We use a Mach-Zehnder interferometer to encrypt experimentally each movie. One arm of the interferometer is the joint transform correlator and the other arm is the reference wave. We include the complete description of the procedure along with experimental results supporting the proposal.

RESUMEN

We demonstrate a smart image-packaging optical technique that uses what we believe is a new concept to save byte space when transmitting data. The technique supports a large set of images mapped into modulated speckle patterns. Then, they are multiplexed into a single package. This operation results in a substantial decreasing of the final amount of bytes of the package with respect to the amount resulting from the addition of the images without using the method. Besides, there are no requirements on the type of images to be processed. We present results that proof the potentiality of the technique.

Asunto(s)

RESUMEN

We introduce a way to encrypt-decrypt a color dynamical phenomenon using a pure optical alternative. We split the three basic chromatic channels composing the input, and then each channel is processed through a 4f encoding method and a theta modulation applied to the each encrypted frame in every channel. All frames for a single channel are multiplexed. The same phase mask is used to encode all the information. Unlike the usual procedure we do not multiplex the three chromatic channels into a single encoding media, because we want to decrypt the information in real time. Then, we send to the decoding station the phase mask and the three packages each one containing the multiplexing of a single channel. The end user synchronizes and decodes the information contained in the separate channels. Finally, the decoding information is conveyed together to bring the decoded dynamical color phenomenon in real-time. We present material that supports our concepts.

RESUMEN

We introduce for the first time the concept of an all-optical encrypted movie. This movie joints several encrypted frames corresponding to a time evolving situation employing the same encoding mask. Thanks to a multiplexing operation we compact the encrypted movie information into a single package. But the decryption of this single package implies the existence of cross-talk if we do not adequately pre-process the encoded information before multiplexing. In this regard, we introduce a grating modulation to each encoded image, and then we proceed to multiplexing. After appropriate filtering and synchronizing procedures applied to the multiplexing, we are able to decrypt and to reproduce the movie. This movie is only properly decoded when in possession of the right decoding key. The concept development is carried-out in virtual optical systems, both for the encrypting and the filtering-decrypting stages. Experimental results are shown to confirm our approach.

RESUMEN

We demonstrate in this Letter that a joint transform correlator shows vulnerability to known-plaintext attacks. An unauthorized user, who intercepts both an object and its encrypted version, can obtain the security key code mask. In this contribution, we conduct a hybrid heuristic attack scheme merge to a Gerchberg-Saxton routine to estimate the encrypting key to decode different ciphertexts encrypted with that same key. We also analyze the success of this attack for different pairs of plaintext-ciphertext used to get the encrypting code. We present simulation results for the decrypting procedure to demonstrate the validity of our analysis.