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Shannon Y Pgp

In: Computers and Technology

Submitted By raul93
Words 950
Pages 4
Confusión-Shannon
La confusión se refiere a hacer la relación entre el texto cifrado y la clave simétrica tan complejo y complicado como sea posible.
Objetivos
Dado que normalmente el criptoanalista sólo dispondrá del texto cifrado y del conocimiento del funcionamiento del algoritmo de cifrado utilizado, intentará dar con la clave secreta. La confusión busca ocultar la relación entre el texto cifrado y la clave secreta.
Los algoritmos de cifrado que se sirven de la confusión y de la difusión se suelen llamar cifradores de producto. Cada aplicación de la confusión y de la difusión se produce en una vuelta de cifrado. Los cifradores modernos suelen utilizar muchas vueltas de cifrado o iteraciones.
Por tanto, si un algoritmo está bien diseñado, pasará como con el candado: un texto cifrado sólo se podrá descifrar si se conoce la clave.
En la buena criptografía se sigue siempre el Principio de Kerckhoffs: la seguridad del sistema debe recaer en la seguridad de la clave, debiéndose suponer conocidos el resto de los parámetros del sistema criptográfico. Como dijo Claude Shannon: “el adversario conoce el sistema”.
PGP
PGP es el acrónimo de Pretty Good Privacy (Privacidad Bastante Buena), un programa desarrollado por Phil Zimmermann que sirve para cifrar contenido y acceder a él mediante una clave pública y firmar documentos digitalmente para autentificarlos. El programa vio la luz en 1991, y desde entonces se ha convertido en una herramienta imprescindible para el cifrado de toda clase de archivos, ya que a pesar de sus más de 20 años de vida, sigue siendo una tecnología de cifrado muy segura. En la actualidad, la tecnología es propiedad de Symantec, pero está disponible a través de una gran cantidad de programas distintos para diferentes plataformas. Además, existe una versión de código abierto cuyo principal representante es la aplicación GnuPG.
Cómo funciona PGP
Intentando no ser demasiado técnico, hay que decir que PGP (Pretty Good Privacy) utiliza cuatro procesos distintos de cifrado (hashing, compresión de datos, cifrado de clave simétrica y cifrado de clave pública) que garantizan la seguridad desde el momento en que cifras un archivo, mensaje o documento y lo descifras. En el proceso de cifrado, se comprime el documento o archivo y se genera una clave aleatoria. Al enviar el paquete de datos se adjunta una clave cifrada con la clave del receptor, que en el momento de descifrar el archivo o documento, realiza el proceso inverso.
Funciones de PGP
La PGP ofrece las siguientes funciones: * Firmas digitales y verificación de la integridad de los mensajes: función que se basa en el uso simultáneo de la función hash (MD5) y del sistema RSA. La función MD5 condensa el mensaje y produce un resultado de 128 bits que después se cifra, gracias al algoritmo RSA, por la clave privada del emisor. * Cifrado de archivos locales: función que utiliza el algoritmo IDEA. * Generación de claves públicas o privadas: cada usuario cifra su mensaje mediante las claves privadas IDEA. La transferencia de las claves electrónicas IDEA utiliza el sistema RSA. Por lo tanto, PGP ofrece dispositivos para la generación de claves adaptados al sistema. El tamaño de las claves RSA se propone de acuerdo con varios niveles de seguridad: 512, 768, 1024 o 1280 bits. * Administración de claves: función responsable de la distribución de la clave pública del usuario a los remitentes que desean enviarle mensajes cifrados. * Certificación de claves: esta función permite agregar un sello digital que garantice la autenticidad de las claves públicas. Es una característica original de PGP, que basa su confianza en una noción de proximidad social en vez de en una entidad de certificación central. * Revocación, desactivación y registro de claves: función que permite producir certificados de revocación.
Programas para utilizar PGP
Hoy en día hay multitud de aplicaciones web y programas de Escritorio o móviles que utilizan la tecnología PGP para cifrar comunicaciones y archivos. Entre la gran variedad disponible, he procurado mencionar los más representativos. * PGP Desktop (ahora Symantec Encryption): El primer programa para usar PGP era PGP Desktop. Sin embargo, tras la adquisición de PGP por parte de Symantec, este programa desapareció, dando paso a una serie de aplicaciones variadas de pago, enfocadas sobre todo a la empresa, y que están enfocadas a distintas posibilidades de PGP, como cifrado de correos electrónicos, cifrado de datos en redes locales o cifrado de discos duros locales. * GnuPG o GPG: Paralelamente al desarrollo de PGP, el mundo open source decidió crear su alternativa libre y gratuita, GnuPG (Gnu Privacy Guard). Esta herramienta, disponible para varias plataformas, incluyendo OS X a través de GPG Suite. Aunque por defecto funciona desde línea de comandos, en su página oficial encontrarás programas con entorno gráfico para usar GPG, acrónimo de GnuPG. * GPGshell: Uno de los programas más populares que utiliza GnuPG para cifrar archivos. Su aspecto es muy simple pero ofrece todas las opciones de GPG pero con menús, ventanas y sin tener que abrir la línea de comandos. * Enigmail: Una extensión para Thunderbird y Seamonkey que permite cifrar mensajes de correo electrónico usando el estándar OpenPGP. Se integra muy bien en estos gestores de correo y permite crear claves distintas por cada cuenta de usuario, entre otras opciones. * GNUPGK: Otro programa que se basa en GnuPG para cifrar y descifrar toda clase de archivos. Entre otras cosas, ofrece soporte para PGP, y además se integra en el menú contextual de Windows para ejecutar las acciones más sencillas directamente desde el botón derecho del ratón.

Referencias http://www.oroyfinanzas.com/2014/01/criptografia-simetrica-sistemas-cifra-clave-secreta/ http://docsetools.com/articulos-educativos/article_10078.html http://hipertextual.com/archivo/2013/08/que-es-pgp-y-para-que-sirve/ http://es.kioskea.net/contents/132-pgp-pretty-good-privacy

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