This research proposes an algorithm to sign messages using the ElGamal asymmetric cryptosystem, called: Digital signature algorithm based on ElGamal, Diffie-Hellman protocol and the number π (DSAπ). This proposal has a high level of security like the DSA standard, in addition, execution times are reduced in relation to it. The Diffie-Hellman protocol and the number π were used in the construction of the digital signature algorithm in conjunction with the Hash-Sha-512 function. Some experiments are presented to provide evidence that the bits on the right side of the decimal point of π appear randomly, such as: a color image was constructed of a string of consecutive bits chosen at random, of the number π. Subsequently, parameters such as: entropy, correlation, discrete Fourier transform, goodness-of-fit test χ2 were evaluated. It is mentioned that an S-box 8×8 is involved in the signature. The sensitivity of the signature was measured, that is, when small changes are made to the sender’s private key, or small changes to the message. Finally, an image was constructed using the signatures of random texts, and subsequently the randomness of its pixels was obtained, to verify that there is no relationship between the different signatures.

Active learning has demonstrated its effectiveness regarding the improvement of the capacities of abstraction, comprehension, and development of cognitive, expression and relationship skills of the students. In this study, the redesign and implementation of an electromagnetism course for engineering students is presented, under the methodology of Backward Design (BD), recognized for its attributes for the development of active learning and its possibility of specifying the fun-damentals and principles of engineering education in the development of syllabus in higher ed-ucation. The purposes of this study were: 1) To implement the Backward Design (BD) methodology to develop argumentative, purposeful and interpretive skills in an electromagnetism course; 2) Design and apply rubrics to evaluate tests and laboratory reports, determine the level that best suits the knowledge, skills and competencies of students. 3) Assess the perception of students regarding the use of the methodology, their contributions to the development and understanding of the concepts of the course. The results of this educational research experience shown that the BD teaching approach was pedagogical and significantly superior to conventional models towards improving knowledge and skills of electromagnetism based on Hake's statistic (h) reached 0.73 that allow us to conclude that there was a learning gain in the students.

In the first wave of COVID-19, up to 20% of patients had skin lesions with variable characteristics. There is no clear evidence of the involvement of the SARS-CoV-2 virus in all the cases; some of these lesions may be secondary to drug hypersensitivity. To analyze the possible cause of the skin lesions, we performed a complete allergology study on 11 patients. One year after recovery from COVID-19, we performed a lymphocyte transformation test (LTT) and Th1/Th2 cytokine secretion assays of PBMC. We included 5 nonallergic patients treated with the same drugs without lesions. Except for one patient who had an immediate reaction to azithromycin, all patients had a positive LTT to at least one of the drugs tested (azithromycin, clavulanic acid, hydroxychloroquine, lopinavir, and ritonavir). None of the nonallergic patients had a positive LTT. We found mixed Th1/Th2 cytokine secretion (IL-4, IL-5, IL-13, and IFN-γ) in patients with skin lesions corresponding to mixed drug hypersensitivity type IVa and IVb. In all cases, we identified a candidate drug as the culprit for skin lesions during SARS-CoV-2 infection, although only three patients had a positive drug challenge. Therefore, it would be reasonable to recommend avoiding the drug in question in all cases.