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The Twofish cipher is a very powerful algorithm with a fairly complex structure that permeates most data parsing and switching and can be easily implemented. The keys of the Two-fish algorithm are of variable length (128, 192, or 256 bits), and the key schedule is generated once and repeated in encrypting all message blocks, whatever their number, and this reduces the confidentiality of encryption. This article discusses the process of generating cipher keys for each block. This concept is new and unknown in all common block cipher algorithms. It is based on the permanent generation of sub keys for all blocks and the key generation process, each according to its work. The Geffe's Generator is used to generate subkeys to make each explicit block a new key that differs from block to block, gaining protection against attacks. Finally, this algorithm works almost like a One-Time Pad. [ABSTRACT FROM AUTHOR]

Information hiding strategies have recently gained popularity in a variety of fields. Digital audio, video, and images are increasingly being labelled with distinct but undetectable marks that may contain a hidden copyright notice or serial number, or even directly help to prevent unauthorized duplication. This approach is extended to medical images by hiding secret information in them using the structure of a different file format. The hidden information may be related to the patient. In this paper, a method for hiding secret information in DICOM images is proposed based on Discrete Wavelet Transform (DWT). Firstly. segmented all slices of a 3D-image into a specific block size and collecting the host image depend on a generated key, secondly selected the block number and slice number, thirdly, the low-high band used for embedding after adding the generated number, fourthly, used the Hessenberg transform on the blocks that portioned the band (low-high) in a specific size. The secret information (image or text) is a binary value. It was embedded by setting the positive value in the diagonal to odd values if the embedded is one and setting it to even if the secret bit is zero. Several tests were applied, such as applying mean square error, peak signal to noise ratio PSNR, and structural similarity index measure SSIM. Some analyses such as adding noise, scaling, and rotation analysis are applied to test the efficiency. The results of the tests showed the strength of the proposed method. [ABSTRACT FROM AUTHOR]