Optical asymmetric image encryption using gyrator wavelet transform

• GWT is as an alternative to information processing tools such as, WT, FWT, FT, FRT.
• The GWT can be effectively applied in optical information security applications.
• As the GT order is increased, all the sub-bands get fused so that it is difficult to visually analyze each sub-band in the ciphertext.
• Attack algorithms cannot be directly applied to extract the security keys.
• The GWT can be applied to 2D and 3D binary, color, and multispectral images.

In this paper, we propose a new optical information processing tool termed as gyrator wavelet transform to secure a fully phase image, based on amplitude- and phase-truncation approach. The gyrator wavelet transform constitutes four basic parameters; gyrator transform order, type and level of mother wavelet, and position of different frequency bands. These parameters are used as encryption keys in addition to the random phase codes to the optical cryptosystem. This tool has also been applied for simultaneous compression and encryption of an image. The system's performance and its sensitivity to the encryption parameters, such as, gyrator transform order, and robustness has also been analyzed. It is expected that this tool will not only update current optical security systems, but may also shed some light on future developments. The computer simulation results demonstrate the abilities of the gyrator wavelet transform as an effective tool, which can be used in various optical information processing applications, including image encryption, and image compression. Also this tool can be applied for securing the color image, multispectral, and three-dimensional images.