Image encryption and decryption using chaotic key sequence generated by sequence of logistic map and sequence of states of Linear Feedback Shift Register

In this paper image encryption and decryption using key sequence {K_i} generated by sequence {K_{1, i}} of logistic map and sequence of states {K_{2, i}} of Linear Feedback Shift Register (LFSR) is proposed. Initially one dimensional sequence is generated in the range of 0 to 1 using logistic map for the bifurcation parameter r and initial value X₀. The generated sequences are multiplied with 255 and bit by bit XOR operation employed on states of 8 bit LFSR to obtain final key sequence {K_i}. So obtained key sequence {K_i} is XORed with 8-bit grayscale image pixels {P_i} to obtain the encrypted image. Performance of the proposed scheme is analyzed by computing Histogram, Entropy, Correlation and MSE (Mean Square Error) between the original and encrypted image. This scheme has been tested for two different 8-bit grayscale images of size 256×256 pixels. Proposed scheme is compared with encryption/decryption using sequence {K_{1, i}} generated using logistic map. Result of histogram plot of encrypted image using proposed scheme is flat and uniformly distributed compared to encryption scheme using generated sequence of logistic map. MSE measured between original and encrypted image found to be high. Also correlation between adjacent pixels of encrypted image found to be low.