The Influence Of Noise And Stolen Keys On Optical Image Encryption And Recognition

The development of traditional information security technology is limited by the processing speed, hardware cost of computer and digital signal processor. The optical image encryption and identification technology can deal with large amounts of data at high speed. In recent years it attracts much attention. In practice, an image may contain different kinds of noises. In reality, partial key leakage may happen. Therefore, it is significant to study the influence of noise and stolen partial keys on optical image encryption and identification.Firstly, based on a joint transform correlator, the influences of different noise and different filtering methods on optical image recognition are studied, respectively. The binary image ‘B’,‘光’and ‘滤’are given as examples. The Gauss noise and the salt and pepper noise are considered, respectively. At the same time, the median filter, the mean filter, and the wiener filter are used, respectively. The corresponding peak-background ratios are given. Results show that for the gauss noise, the wiener filter is the relatively better ones, and for the salt and pepper noise, the median filter is the relatively better ones. Therefore, an optional filter should be chosen according to the properties of noises to improve recognition performance.Secondly, the influences of stolen partial keys and noises on optical image encryption are studied. Using quick-response(QR) code, the text-image is as an example. The content of a text is converted to binary data with QR code. With the same methods of encryption and decryption, studies comparing the original image encryptions with the generated image ones based on QR code are given. Results show that at the same level of partial key leakage, more information will lose for the encryption method with QR code than that without QR code. Therefore the former needs higher-security requirements for keys.Finally, an optical encryption and identification protocol based on phase correlation is proposed. The influence of stolen partial keys on this system is studied. Results show that the mean peak-background ratio(the mean correlation peak intensity) rapidly decreases as the key amount deceases. Even for relatively larger stolen key amount, the value of mean peak-background ratio is relatively smaller, so the optical encryption and identification system has high security. Therefore it is a novel optical encryption and identification system.