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

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.

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 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.