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Practical Constructions of Symmetric-Key Primitives
Published in Jonathan Katz, Yehuda Lindell, Introduction to Modern Cryptography, 2020
The core of ChaCha20 is a fixed permutation P that operates on 512-bit strings. This permutation is carefully constructed to be both highly efficient and “cryptographically strong.” To improve efficiency, it was designed to rely primarily on only three assembly-level instructions operating on 32-bit words: Addition (modulo 232), bitwise (cyclic) Rotation, and XOR; P is thus an example of what is called an ARX-based design. From a cryptographic point of view, P is intended to be a suitable instantiation of a “random permutation,” and constructions based on P can be analyzed in the so-called random-permutation model. By analogy with the random-oracle model (see Section 6.5), the random-permutation model assumes that all parties are given access to oracles for a uniform permutation P as well as its inverse P−1. In this model, as in the random-oracle model, the only way to compute P (or P−1) is to explicitly query those oracles. (We refer to Section 7.3.3 for an example of a proof of security in the random-permutation model.)
New approach for attack of permutation-based image encryption schemes
Published in International Journal of Computers and Applications, 2021
Tahar Mekhaznia, Akram Bennour
The first case illustrates various steps of decryption of the ‘Cat’ image. The image has 300 × 400 pixels, 17.5 Ko disc size and encloses 22 colors. It has been encrypted by a pseudo-random permutation algorithm. Figure 10 illustrates various stages of ciphertext and plaintext forms after the localization of pixels of each color (Figure 10b–v) starting from a ciphertext (Figure 10a). The marked color used is the black one. The final result is shown in Figure 10w where all ciphertext pixels are marked with black (Ic_level = 0). The whole stages of execution have been accomplished during 321 iterations (6.8 s of processing time, excluding the Output display of intermediate layers). We note that the result becomes perceptible with less than a dozen of stages (Figure 10h) where it appears unnecessary to extend the execution until the whole plaintext recovery.
Estimation of distribution algorithm with path relinking for the blocking flow-shop scheduling problem
Published in Engineering Optimization, 2018
Zhongshi Shao, Dechang Pi, Weishi Shao
To enhance the exploitation of EDA, a local search is implemented to quickly lead the current new individual towards the promising area. To solve the BFSP with the makespan criterion, Wang et al. (2010) presented an RLS, which has been adopted in other algorithms (Wang, Pan, and Tasgetiren 2011; Pan et al.2013). In RLS, denotes the reference sequence. Usually, the best individual or a random permutation of all jobs is selected as the reference sequence. The process of RLS is shown as follows. Suppose that the current individual is . First, the RLS removes job , , from the current individual and inserts it into all possible slots of . Then, find the slot j with the lowest makespan and insert job into the slot j of to generate a new individual . Finally, if is better than , will be replaced by . Repeat this procedure until no better solutions are obtained.
3-min whole body cryotherapy/cryostimulation after training in the evening improves sleep quality in physically active men
Published in European Journal of Sport Science, 2019
Wafa Douzi, Olivier Dupuy, Maxence Tanneau, Geoffroy Boucard, Romain Bouzigon, Benoit Dugué
The experiment was held for two weeks. Each session occurred once per week on the same weekday and at the same time during the day (starting at 7 pm). Subjects undertook a standardized training session for 55 min. Then, each subject was assigned to a 3-min whole-body cryotherapy session using a recently described chamber (AuroreConcept®, Noisels, France) (Bouzigon et al., 2017) or 3-min passive recovery (participant were seated) in a random order. The randomization was performed using random permutation tables, generated by a computer algorithm. The night following the recovery (cryotherapy or passive), subjects wore accelerometers and heart rate monitors and recorded their bedtime and waking time in a logbook.