Medical image encryption based on biometric keys and lower-upper decomposition with partial pivoting.

The security of medical image transmission in telemedicine is very important to patients' privacy and health. A new asymmetric medical image encryption scheme is proposed. The medical image is encrypted by two spiral phase masks (SPM) and the lower-upper decomposition with partial pivoting, where the SPM is generated from the iris, chaotic random phase mask, and amplitude truncated spiral phase transformation. The proposed scheme has the following advantages: First, the iris is used for medical image encryption, which improves the security of the encryption scheme. Second, the combination of asymmetric optical encryption and three-dimensional Lorenz chaos improves the key space and solves the linear problem based on double-random phase encoding. Third, compared with other encryption schemes, the proposed scheme has advantages in occlusion attacks, key space, correlation, and information entropy. Numerical simulation and optical results verify the feasibility and robustness of the encryption scheme.