TOTP is a prevalent industrial and environmental contaminant which has been shown to be a neurotoxic agent. This study was undertaken to investigate the effects of this compound on the immune system. Several techniques were employed to test the humoral as well as cellular effects. Male Swiss Webster mice were administered by gastric gavage with three doses of TOTP (5, 50, and 500 mg/kg) and one dose TMTP (50 mg/kg) in corn oil once a week for 13 weeks. Control animals were given corn oil alone. Lymphocyte transformation was determined on cultures of splenic cells obtained from animals sacrificed at 1, 4, 8, and 13 weeks. Relative Proliferation Index (RPI) and Stimulation Index (SI) was calculated for phytohemagglutinin (PHA), pokeweed (PWM), and lipopolysaccharide (LPS) mitogen treated cultures. Proliferation was measured by uptake of radioisotope labeled thymidine. Plaque formation as well as delayed hypersensitivity was evaluated at all dose levels after 4 weeks of treatment. Humoral effects were determined utilizing quantitative (Rocket) immunoelectropheresis. Serum was compared with control serum for IgA, IgG, and IgM fractions. TOTP was found to cause slight suppression in proliferation of splenic lymphocytes at 8 and 13 weeks although this suppression was non-specific and not dose related. No effects were seen on body and organ weights. Plaque forming cells and delayed hypersensitivity were not affected either by dose or time of treatment. Immunoglobulin fractions tested were similarly not affected by time or dosage. These findings suggest that neither TOTP nor TMTP exhibit immunotoxic effects at levels used.

This thesis is focused on authentication methods, for regular private users and company solutions. Based on the analysis of individual authentication methods discussed in a theoretical part, the most suitable solutions are chosen. The practical part then offers various solutions divided into categories based on the users profiles. This presented overview suggests possible follow up discussion topics and an outline of the future development in the area of authentication methods and tools.

Multi-factor authentication is a term that was foreign until a few years ago. But in reality, it has been around for decades in the world of computer security. In theory, has the purpose to improve the security of user authentication by adding an extra layer of security to the process. Although password authentication has been shown to be an imperfect technique, it is still the most widely used today. That is why this research has been carried out, to shed light on the issue of why multi-factor authentication is not a fundamental pillar in security. For this, two promising protocols of the second authentication factor have been chosen, Time-based One-time Password (TOTP) and Universal 2nd Factor (U2F), and the usability of these methods has been compared together with password authentication usability as well. A Systematic Literature Review has been executed to answer the raised research question. Although the setup and login processes of the protocols are excessively slow, the results show that the U2F devices are overall more usable than TOTP, as they have a more “friendly” daily usage. But not enough data has been found on TOTP to be able to make a comparison with a solid basis. / La autenticación de múltiples factores es un término que era extraño hasta hace varios años. Pero en realidad, ha existido durante décadas en el mundo de la seguridad informática. En teoría, su objetivo es mejorar la seguridad del proceso de autenticación de usuarios, agregando una capa adicional de seguridad al proceso. Aunque se ha demostrado que la autenticación de contraseña es una técnica imperfecta, sigue siendo la más utilizada en la actualidad. Esta es la razón por la que se ha realizado esta investigación, para arrojar luz sobre el tema de por qué la autenticación de múltiples factores no es un pilar fundamental en la seguridad. Para ello, se han elegido dos protocolos prometedores del segundo factor de autentificación, como son, Time-based One-time Password (TOTP) y Universal 2nd Factor (U2F), y se ha comparado la usabilidad de estos métodos junto con usabilidad de la autenticación por contraseña. Se ha realizado una Revisión Sistemática de la Literatura (Systematic Literature Review) para dar respuesta a la pregunta de investigación planteada. Aunque los procesos de configuración e inicio de sesión de los protocolos son excesivamente lentos, los resultados muestran que los dispositivos U2F son en general mas usables ya que tienen un uso diario más “amigable”. Pero no se han encontrado suficientes datos sobre TOTP para poder hacer una comparación con una sólida base. / <p><strong>Laburpena</strong> [Summary/Abstract, Basque/baskiska]</p><p>Faktore-anitzeko autentifikazioa orain dela urte gutxi arte arrotza izan den terminoetako bat da. Baina, egia esan, hamarkada batzuk daramatza segurtasun informatikoaren munduan errotua. Teorian, erabiltzaileen autentifikazio-prozesuaren segurtasuna hobetzeko helburu du, prozesuari segurtasun-geruza berri bat gehituz. Pasahitz autentifikazio teknika inperfektua dela frogatu bada ere, gaur egun oraindik erabiliena da. Horregatik egin da ikerketa hau, faktore anitzeko autentifikazioa zergatik ez den segurtasunaren oinarrizko zutabea argitzeko. Horretarako, faktore-anitzeko autentifikazio barruan aurkitzen diren bi protokolo itxaropentsu aukeratu dira, hala nola, Time-based One-time Password (TOTP) eta Universal 2nd Factor (U2F), eta hauen erabilgarritasuna konparatu da pasahitz bidezko erabilgarritasunarekin batera. Planteatutako ikerketa galderari erantzuteko Literatura Ikerketa Sistematikoa (Systematic Literature Review) burutu da, protokolo bakoitzaren onurak/eragozpenak bilduz eta hauen arteko konparaketa bat eginez. Protokoloen konfigurazio eta saioa hasteko prosezuak motelegiak badira ere, emaitzek erakusten dute U2F gailuak orokorreak TOTP baino erabilgarriagoak direla, eguneroko erabilera “lagunartekoagoa” baitute. Baina ez da datu nahikorik aurkitu TOTP-en oinarri sendo batekin konparazio bat egin ahal izateko.</p><p><strong>HITZ-GAKOAK:</strong> autentifikazioa, faktore-anitzeko autentifikazioa, Universal 2nd Factor, U2F, Time-based One-time Password, TOTP, alderaketa, erabilgarritasuna</p>