46results about How to "Expand the key space" patented technology

An asymmetric double-image encryption method based on a fractional Fourier domain phase recovery procedure comprises the steps of pure phase extraction, phase modulation and fractional Fourier transform. The asymmetric double-image encryption method based on the fractional Fourier domain phase recovery procedure is applied to double-image encryption, the encryption process is different from the decryption process, an encryption key is different from a decryption key, and the defects that a traditional symmetric encryption algorithm is easy to attack and an encryption key is the same as a decryption key are overcome. Through attack tests, it is proved that the method is high in resistance to violent attacks, noise attacks and other specific attacks. Meanwhile, key space is large, the problem that a traditional encryption algorithm is insufficient in key space is solved, the decryption process can be realized through an optical method, and a system is simple and convenient to operate.

The present invention provides a biometrics-based cryptographic key generation system and method. A user-dependent distinguishable feature transform unit provides a feature transformation for each authentic user, which receives N-dimensional biometric features and performs a feature transformation to produce M-dimensional feature signals, such that the transformed feature signals of the authentic user are compact in the transformed feature space while those of other users presumed as imposters are either diverse or far away from those of the authentic user. A stable key generation unit receives the transformed feature signals to produce a cryptographic key based on bit information respectively provided by the M-dimensional feature signals, wherein the length of the bit information provided by the feature signal of each dimension is proportional to the degree of distinguishability in the dimension.

The invention discloses an encryption and decryption method based on coupling and self-triggering cellular automata. The encryption and decryption method comprises: according to the properties of the coupling and self-triggering cellular automata, adopting n interactional cellular automata as an entirety, and constructing an encryption and decryption system of coupling and self-triggering cellular automata. A simulation experiment result indicates that the algorithm greatly improves the key space and effectively prevents brute force attack; and meanwhile, when a random number is introduced in an encryption process to prevent an attacker from obtaining an exclusive plaintext and ciphertext pair, so that known plaintext attach and selective ciphertext attach are effectively prevented.

The present invention relates to a DNA dynamic coding based colored image encryption method, comprising: obtaining a key through a colored plain-text image; by the key, calculating an initial value and a parameter of a chaotic system used in scrambling and diffusion processes; substituting the initial value and the parameter to the chaotic system for iteration to obtain W1 and W2, obtaining a scrambling matrix K from W1, obtaining an integer matrix Y and an index matrix Ind from W2, and performing DNA coding on Y according to the index matrix Ind; and performing scrambling on the plain-text image row by row by using the matrix K, then performing coding and diffusion until all rows finish DNA coding, and finally performing decoding and recomposing on a DNA matrix, to obtain a final colored ciphertext image. According to the method, a function SHA256 is used to generate the key, so that the key space is expanded; the generation of the key depends on a plain-text, so that plain-text attack can be effectively resisted; chaotic characteristics are combined with DNA dynamic coding, so that the security is further improved; and meanwhile, scrambling and diffusion operations are performed according to the row of images, so that parallel computing is facilitated and the efficiency is improved.

The invention discloses a novel digital image encryption method belonging to the field of DNA calculation and image encryption, and provides a digital image encryption method based on a DNA sequence and multi-chaotic mapping. The traditional encryption algorithm based on chaos has the defects that a key space is small, a chaos system is easy to analyze and forecast, and the like; and almost of the current encryption systems based on DNA need complex biological operation and are hard to realize. In order to overcome the defects, the invention provides the digital image encryption method based on a DNA sequence and multi-chaotic mapping, comprising the following steps of: firstly, scrambling the positions of pixels of images by utilizing a two-dimension chaotic sequence generated by Cubic mapping and Haar wavelet functions, and then disrobing the pixel values of the images under the action of a chaotic sequence generated by the DNA sequence and the Logistic mapping. The experimental result shows that the algorithm is easy to realize, has better encryption effect on images, large key space and high sensitivity to keys and can effectively resist exhaustive attack and statistical attack.

The invention discloses a color image encryption and decryption method based on multiple-fractional-order chaotic systems. An encryption algorithm comprises an original image scrambling stage and a scrambling image encryption stage. Firstly, two different fractional-order chaotic systems are utilize to generate three scrambling arrays and respectively process R, G and B three primary color component arrays of an original color image I0 in a scrambling mode to obtain scrambled image I1. Furthermore, another two different fractional-order chaotic systems are utilize to generate three secret key arrays and carries out exclusive OR operation on elements on the secret key arrays and pixel of the scrambled image I1 one by one to change values of all pixel points of the scrambled image I1 to obtain encrypted image I2, and the image decryption is a reversed process of the encryption. The method uses the multiple-fractional-order chaotic systems so as to greatly enhance safety. Furthermore, the algorithm secret keys are large in space, high in secret key sensitiveness and strong in impact resistance.

A multi-image encryption method based on piecewise linear chaotic map (PWLCM) belongs to the field of information encryption, and aims to solve the problems that most of the conventional image encryption methods take a single image as an encryption object, and cannot adapt to mass image encryption, and the encryption efficiency of the conventional image encryption methods is relatively low. Being different to the conventional image encryption methods, the multi-image encryption method takes multiple images as encryption objects, and adopts the steps of converting the multiple images into a single large image, encrypting the single large image, and converting the encrypted single large image into multiple encrypted images, so as to protect contents in the multiple images. The multi-image encryption method comprises the key steps of combining k interactive images into a large image, encrypting the large image according to PWLCM to obtain an encrypted large image, dividing the encrypted large image into k encrypted images, and naming the k encrypted images sequentially according to a chaotic sequence generated based on PWLCM. Test results show that the method is easy to implement, the encryption effect is favorable, the encryption efficiency and security are high, and communication security of contents of any multiple images can be protected simultaneously.

The invention relates to an intra-class coefficient scrambling-based JPEG image encryption method. The method comprises the following steps: firstly reading in a JPEG image file, acquiring a Huffman coding table and image data which undergoes JPEG coding compression, carrying out decoding to acquire all the non-zero quantized DCT coefficient numerical values and positions and carrying out classification; selecting a password, carrying out chaotic iteration by utilizing the password, so as to generate a chaotic sequence, and scrambling the non-zero coefficients and 8*8 block of each class by utilizing the chaotic sequence; and carrying out entropy coding on a scrambled quantized DCT coefficient matrix, and writing the coded data into the JPEG image file so as to complete intra-class coefficient scrambling-based JPEG image encryption. According to the method disclosed in the invention, scrambling is carried out on different classes of quantized DCT coefficients through the chaotic sequence, and the quantized DC coefficients and the non-zero AC coefficients are processed by directly using one encryption scheme, so that the safety and the high efficiency are both considered; and the encrypted images are similar to clear text image files in the aspect of size, and have high compression ratios.

The invention discloses a method for constructing a new chaotic system based on a fractal algorithm, which includes selecting a three-dimensional chaotic system and taking the chaotic sequence generated by it as the input sequence of the fractal algorithm; applying the obtained chaotic sequence to the ternary fractal algorithm to obtain the final A new type of fractal chaotic system. The construction method of this new type of chaotic system based on fractal algorithm provided by the present invention can construct many different chaotic systems by selecting different chaotic subsystems and increasing the number of fractals, which can not only improve the key space of the system, but also improve the applicability Strong, high flexibility.

The invention relates to a physical layer encryption method that introduces a Latin matrix. Use the chaotic system and Latin matrix to generate a key with good performance, and then use the key to scramble the constellation diagram to make the distribution of constellation points of different modulation methods on the complex plane tend to be uniform, and then the individual characteristic parameters of different modulation methods will tend to be uniform. In the same way, the purpose of protecting the modulation method and modulation information from the physical layer is achieved. Make full use of the mapped complex plane information to greatly expand the key space. By introducing the Extract function, the correlation between chaotic sequences is fully eliminated, and the key space is ensured without generating a large number of keys, which greatly reduces the complexity of hardware implementation and performs NIST randomness testing on the generated keys. , verify its unpredictability.

The present invention is a chaotic optical communication transceiver with a large key space, which belongs to the technical field of secure optical communication; the key space is increased by increasing the number of external cavities, the structure is complex, and it is susceptible to environmental interference, and the pseudo-random code modulation increases the key space and cannot play chaos The unique hardware encryption advantage of secure communication increases the complexity of the feedback loop and increases the key space, which is expensive and inconvenient for integration and large-scale production; the present invention provides a chaotic optical communication transceiver with a large key space, and the key space is DFB semiconductor The laser feedback intensity, driving current and key parameters of the random filter module are combined. The random filter module replaces the traditional feedback mirror to realize the random selection function after the optical path range is encoded to the spectrum, which greatly improves the key space of the chaotic optical communication transceiver and meets the legal requirements. The confidential communication of users increases the difficulty of stealing by illegal users, effectively hides delay characteristics, ensures hardware consistency, facilitates chaotic synchronization, and facilitates large-scale production.