The document discusses network security principles such as cryptography, authentication, and message integrity. It explains symmetric key cryptography where senders and receivers share the same key, and public key cryptography where users have a public key for encrypting messages and a private key for decrypting. The document also outlines common attacks like eavesdropping, message insertion, and denial of service and how techniques like encryption, firewalls, and access control can help address security threats.
The document summarizes key concepts in network security including cryptography, authentication, integrity, and access control. It discusses principles like confidentiality, authentication, and integrity. It introduces common examples of Alice, Bob, and Trudy to illustrate security concepts and the need to protect against eavesdropping, impersonation, message alteration, and denial of service attacks. Symmetric and public key cryptography algorithms are overviewed including DES, AES, and RSA.
The document discusses various topics related to network security including encryption, authentication, and protocols. It provides an overview of symmetric and public key cryptography, algorithms like DES and RSA, digital signatures, protocols like SSL and IPsec, and applications like PGP. Common security threats like packet sniffing, IP spoofing, and denial of service attacks are also summarized.
Encryption obscures information to authorize access while hiding it from others. Private key encryption uses a shared key while public key encryption uses separate keys for encryption and decryption. Digital signatures authenticate information through encryption with a private key. Key management creates, distributes, certifies, protects, and revokes keys, while hierarchical and web of trust models establish trust in encryption systems.
This document discusses enhancing security in DNA-based cryptography. It describes how DNA can be used to store encrypted data by encoding messages in DNA strands using an alphabet of short DNA sequences. The document outlines several methods for DNA-based cryptography including DNA steganography systems that hide encrypted messages within collections of DNA strands. It also summarizes the RSA encryption algorithm and describes challenges in DNA-based cryptography systems like preventing unauthorized access and protecting against cryptanalysis. The document concludes that initial investigations show DNA cryptography methods can in principle be unbreakable but also discusses ways to improve security.
Cryptography for Developers provides an overview of cryptography concepts for developers. It defines cryptography as the encryption of plaintext into ciphertext and back again. It discusses symmetric and asymmetric cryptography, including examples like the Caesar cipher. It covers hashing of passwords for storage and discusses popular algorithms like MD5 and SHA-2. The document also summarizes public key cryptography techniques like RSA and references materials for further learning.
Cupdf.com public key-cryptography-569692953829ajsk1950
This document provides an overview of public key cryptography. It discusses how public key cryptography uses asymmetric key pairs, with one key used for encryption and the other for decryption. One key is public and accessible, while the other is private. It also discusses how digital signatures use public key cryptography to authenticate the sender of a message. The document provides examples to illustrate how public key encryption and digital signatures work. It discusses issues like key management and risks associated with public key cryptography.
Public key cryptography uses key pairs - a public key and a private key - to encrypt and decrypt messages. The public key can be shared widely, while the private key is kept secret. This allows users to securely share encrypted messages without having to first share secret keys. Common applications of public key cryptography include public key encryption and digital signatures.
The document discusses network security principles such as cryptography, authentication, and message integrity. It explains symmetric key cryptography where senders and receivers share the same key, and public key cryptography where users have a public key for encrypting messages and a private key for decrypting. The document also outlines common attacks like eavesdropping, message insertion, and denial of service and how techniques like encryption, firewalls, and access control can help address security threats.
The document summarizes key concepts in network security including cryptography, authentication, integrity, and access control. It discusses principles like confidentiality, authentication, and integrity. It introduces common examples of Alice, Bob, and Trudy to illustrate security concepts and the need to protect against eavesdropping, impersonation, message alteration, and denial of service attacks. Symmetric and public key cryptography algorithms are overviewed including DES, AES, and RSA.
The document discusses various topics related to network security including encryption, authentication, and protocols. It provides an overview of symmetric and public key cryptography, algorithms like DES and RSA, digital signatures, protocols like SSL and IPsec, and applications like PGP. Common security threats like packet sniffing, IP spoofing, and denial of service attacks are also summarized.
Encryption obscures information to authorize access while hiding it from others. Private key encryption uses a shared key while public key encryption uses separate keys for encryption and decryption. Digital signatures authenticate information through encryption with a private key. Key management creates, distributes, certifies, protects, and revokes keys, while hierarchical and web of trust models establish trust in encryption systems.
This document discusses enhancing security in DNA-based cryptography. It describes how DNA can be used to store encrypted data by encoding messages in DNA strands using an alphabet of short DNA sequences. The document outlines several methods for DNA-based cryptography including DNA steganography systems that hide encrypted messages within collections of DNA strands. It also summarizes the RSA encryption algorithm and describes challenges in DNA-based cryptography systems like preventing unauthorized access and protecting against cryptanalysis. The document concludes that initial investigations show DNA cryptography methods can in principle be unbreakable but also discusses ways to improve security.
Cryptography for Developers provides an overview of cryptography concepts for developers. It defines cryptography as the encryption of plaintext into ciphertext and back again. It discusses symmetric and asymmetric cryptography, including examples like the Caesar cipher. It covers hashing of passwords for storage and discusses popular algorithms like MD5 and SHA-2. The document also summarizes public key cryptography techniques like RSA and references materials for further learning.
Cupdf.com public key-cryptography-569692953829ajsk1950
This document provides an overview of public key cryptography. It discusses how public key cryptography uses asymmetric key pairs, with one key used for encryption and the other for decryption. One key is public and accessible, while the other is private. It also discusses how digital signatures use public key cryptography to authenticate the sender of a message. The document provides examples to illustrate how public key encryption and digital signatures work. It discusses issues like key management and risks associated with public key cryptography.
Public key cryptography uses key pairs - a public key and a private key - to encrypt and decrypt messages. The public key can be shared widely, while the private key is kept secret. This allows users to securely share encrypted messages without having to first share secret keys. Common applications of public key cryptography include public key encryption and digital signatures.
Jaimin chp-8 - network security-new -use this - 2011 batchJaimin Jani
The document discusses cryptography concepts including symmetric and asymmetric encryption algorithms like DES, AES, RSA. It explains the basic working principles of RSA including key generation using large prime numbers, modular arithmetic and the concept of one-way functions that make private key derivation difficult. It also covers cryptographic modes of operation like ECB, CBC that are used to encrypt data blocks of arbitrary length.
Public key cryptography uses asymmetric encryption with two related keys - a public key and a private key. The public key can be shared openly but the private key is kept secret. When Alice wants to send a confidential message to Bob, she encrypts it with Bob's public key. Only Bob can decrypt it using his private key. Public key infrastructure involves policies and technologies for issuing, managing, and revoking digital certificates that bind public keys to identities. Popular public key algorithms like RSA are based on the difficulty of factoring large prime numbers.
Network security relies heavily on cryptography, which transforms messages to make them secure. There are two main categories of cryptography: symmetric-key cryptography where the same key is used to encrypt and decrypt, and asymmetric-key cryptography where different keys are used for encryption and decryption. Traditional symmetric-key ciphers include substitution ciphers that replace symbols and transposition ciphers that rearrange symbols. Modern symmetric-key ciphers operate on bits and are more complex.
Blockchain privacy approaches in hyperledger indyManishKumarGiri2
Hyperledger Indy provides privacy-preserving identity solutions using distributed ledger technology. It uses several cryptographic techniques like elliptic curve cryptography, zero-knowledge proofs, and authenticated encryption. Zero-knowledge proofs allow a prover to prove possession of certain information to a verifier without revealing the information itself. Hyperledger Indy implements zero-knowledge proofs using zk-SNARKs and Idemix to privately verify credential information. It also uses Libsodium's sealed boxes for anonymous messaging and credential revocation features to preserve privacy in credentials over time. These approaches help Hyperledger Indy provide private and decentralized identity solutions on blockchains.
Hybrid encryption combines asymmetric and symmetric encryption algorithms to provide increased security. It uses a public key algorithm like RSA to encrypt a randomly generated symmetric key, which is then used with a symmetric algorithm like AES to encrypt the plaintext. The encrypted symmetric key is sent along with the encrypted plaintext. To decrypt, the recipient uses their private key to recover the symmetric key and decrypts the ciphertext with that key. Hybrid encryption leverages the strengths of both types of algorithms to improve security compared to either one alone.
The document discusses digital signatures and related cryptographic concepts. It introduces El Gamal and RSA algorithms for digital signatures, and how they use public/private key pairs to sign and verify messages. It also discusses hashing functions and how they are used to generate digests of messages for signing rather than signing full messages. The Secure Hash Algorithm (SHA) and Digital Signature Algorithm (DSA) are presented as common standards. The properties and process of DSA signature generation and verification are described in detail.
Encryption is a process that converts plain text into ciphertext through the use of cryptographic algorithms and encryption keys. There are two main types of encryption: symmetric encryption which uses the same key for encryption and decryption, and asymmetric encryption which uses a public key for encryption and a private key for decryption. Common symmetric encryption algorithms discussed include DES, Triple DES, AES, Blowfish and Twofish. Asymmetric algorithms include RSA. Other algorithms mentioned are IDEA, MD5, and FPE. The document also discusses how encryption keys are used and changed in Magento.
This document analyzes and compares the performance of various cryptography algorithms. It discusses symmetric key algorithms like DES, AES, Blowfish and IDEA as well as asymmetric algorithms like RSA and Diffie-Hellman. The performance is evaluated based on parameters like encryption/decryption time, memory usage and throughput. Experiments show that Blowfish has better performance than AES for encrypting audio files, with lower average encryption and decryption times. In conclusion, cryptography is important for network security and Blowfish performs encryption/decryption more efficiently than AES for audio files.
Principles of public key cryptography and its UsesMohsin Ali
This document discusses the principles of public key cryptography. It begins by defining asymmetric encryption and how it uses a public key and private key instead of a single shared key. It then discusses key concepts like digital certificates and public key infrastructure. The document also provides examples of how public key cryptography can be used, including the RSA algorithm and key distribution methods like public key directories and certificates. It explains how public key cryptography solves the key distribution problem present in symmetric encryption.
What is cryptography,its types,two algorithms i.e RSA and DES.
explained well and referenced the slide share too to give more precise presentation. Thank you.
AES (Advanced Encryption Standard) is a symmetric block cipher algorithm that was adopted as a replacement for the DES (Data Encryption Standard) algorithm. AES is considered more secure than DES due to using a larger key size and being more computationally difficult to break. While AES is fast and reliable for encrypting files and documents, it is not suitable for encrypting communications due to the key exchange problem - for that, an asymmetric algorithm like RSA is typically used to securely exchange the AES key.
Twenty years of attacks on the rsa cryptosystemlinzi320
- The document surveys various attacks on the RSA cryptosystem over the past 20 years.
- It describes some elementary attacks, such as using a common modulus for multiple users or blinding signatures, which illustrate improper implementations of RSA.
- It also summarizes Wiener's 1994 attack, which shows that if the private exponent d is too small (less than N1/4), it can be efficiently recovered, breaking the system. The attack uses continued fraction approximations to recover d.
Cryptography is the art and science of securing communication and information by encrypting and decrypting data. It allows for secure transmission of data through both symmetric and asymmetric encryption methods as well as ensuring the integrity, confidentiality and authenticity of digital information. Modern cryptography plays a crucial role in network security through protocols like SSL/TLS that protect internet communication and transactions.
This document provides an overview of data encryption. It defines encryption as disguising information so that only those with the key can recover it. Encryption involves encrypting cleartext into ciphertext using an encryption key. Symmetric encryption uses the same key for encryption and decryption, while asymmetric encryption uses different keys. Encryption methods include transposition, which rearranges bits or characters, and substitution, which replaces them. The document discusses the Data Encryption Standard (DES) and RSA public key cryptosystem algorithms. It concludes that public key encryption can provide both privacy and authentication.
This document summarizes a talk on proxy cryptography given by Anca-Andreea Ivan and Yevgeniy Dodis at NDSS 2003. It introduces the problem of allowing one party (Bob) to decrypt ciphertexts or sign messages on behalf of another party (Alice) without knowing Alice's secret key. This is achieved using a third party (Escrow) and proxy functions. The talk aims to formally define proxy functions and construct simple schemes satisfying the definitions. It outlines related work and compares the authors' formal approach to previous work. It then defines unidirectional and bidirectional proxy functions for both encryption and signatures and presents generic and specialized constructions satisfying security definitions.
A 2,000-BIT MESSAGE IS USED TO GENERATE A 256-BIT HASH. ONE THE AVERAGE, HOW ...SophiaMorgans
1. The document provides 20 questions related to cryptography concepts such as hash functions, encryption algorithms (RSA, DES, 3DES), and digital signatures.
2. Questions cover topics like determining the key length needed to increase cracking time for a brute force attack, using asymmetric encryption to provide a digital signature, and comparing symmetric and asymmetric encryption algorithms.
3. Answers require applying mathematical and conceptual knowledge of cryptography standards and best practices.
The document discusses various topics related to security in e-commerce including cryptography mechanisms like symmetric and asymmetric encryption, hashing functions, and encryption algorithms like DES, AES, and RSA. It also covers security protocols like SSL/TLS, SET, S/MIME, and SSH. IPSec and its components AH, ESP and IKE are explained. The IKE phases including phase 1 for mutual authentication and phase 2 for establishing session keys are summarized.
Introduction to and survey of TLS security (BsidesHH 2014)Aaron Zauner
This document provides an introduction and survey of Transport Layer Security (TLS). It begins with motivations for studying TLS and provides background information on topics like cryptography, the TLS handshake process, and cipher suites. The document then discusses the history of TLS and examples of attacks against it. It aims to educate about TLS security and the ongoing efforts by the Internet Engineering Task Force (IETF) to improve TLS mitigations against modern threats.
1) O documento discute as mudanças necessárias na educação para se adaptar à sociedade mais interconectada, com foco na flexibilidade e na integração das novas tecnologias.
2) As dificuldades para a mudança na educação incluem desigualdades, falta de modelos avançados e contradições entre teoria e prática.
3) É necessário que educadores, administradores e alunos estejam abertos à mudança para que ela ocorra de forma efetiva.
Jaimin chp-8 - network security-new -use this - 2011 batchJaimin Jani
The document discusses cryptography concepts including symmetric and asymmetric encryption algorithms like DES, AES, RSA. It explains the basic working principles of RSA including key generation using large prime numbers, modular arithmetic and the concept of one-way functions that make private key derivation difficult. It also covers cryptographic modes of operation like ECB, CBC that are used to encrypt data blocks of arbitrary length.
Public key cryptography uses asymmetric encryption with two related keys - a public key and a private key. The public key can be shared openly but the private key is kept secret. When Alice wants to send a confidential message to Bob, she encrypts it with Bob's public key. Only Bob can decrypt it using his private key. Public key infrastructure involves policies and technologies for issuing, managing, and revoking digital certificates that bind public keys to identities. Popular public key algorithms like RSA are based on the difficulty of factoring large prime numbers.
Network security relies heavily on cryptography, which transforms messages to make them secure. There are two main categories of cryptography: symmetric-key cryptography where the same key is used to encrypt and decrypt, and asymmetric-key cryptography where different keys are used for encryption and decryption. Traditional symmetric-key ciphers include substitution ciphers that replace symbols and transposition ciphers that rearrange symbols. Modern symmetric-key ciphers operate on bits and are more complex.
Blockchain privacy approaches in hyperledger indyManishKumarGiri2
Hyperledger Indy provides privacy-preserving identity solutions using distributed ledger technology. It uses several cryptographic techniques like elliptic curve cryptography, zero-knowledge proofs, and authenticated encryption. Zero-knowledge proofs allow a prover to prove possession of certain information to a verifier without revealing the information itself. Hyperledger Indy implements zero-knowledge proofs using zk-SNARKs and Idemix to privately verify credential information. It also uses Libsodium's sealed boxes for anonymous messaging and credential revocation features to preserve privacy in credentials over time. These approaches help Hyperledger Indy provide private and decentralized identity solutions on blockchains.
Hybrid encryption combines asymmetric and symmetric encryption algorithms to provide increased security. It uses a public key algorithm like RSA to encrypt a randomly generated symmetric key, which is then used with a symmetric algorithm like AES to encrypt the plaintext. The encrypted symmetric key is sent along with the encrypted plaintext. To decrypt, the recipient uses their private key to recover the symmetric key and decrypts the ciphertext with that key. Hybrid encryption leverages the strengths of both types of algorithms to improve security compared to either one alone.
The document discusses digital signatures and related cryptographic concepts. It introduces El Gamal and RSA algorithms for digital signatures, and how they use public/private key pairs to sign and verify messages. It also discusses hashing functions and how they are used to generate digests of messages for signing rather than signing full messages. The Secure Hash Algorithm (SHA) and Digital Signature Algorithm (DSA) are presented as common standards. The properties and process of DSA signature generation and verification are described in detail.
Encryption is a process that converts plain text into ciphertext through the use of cryptographic algorithms and encryption keys. There are two main types of encryption: symmetric encryption which uses the same key for encryption and decryption, and asymmetric encryption which uses a public key for encryption and a private key for decryption. Common symmetric encryption algorithms discussed include DES, Triple DES, AES, Blowfish and Twofish. Asymmetric algorithms include RSA. Other algorithms mentioned are IDEA, MD5, and FPE. The document also discusses how encryption keys are used and changed in Magento.
This document analyzes and compares the performance of various cryptography algorithms. It discusses symmetric key algorithms like DES, AES, Blowfish and IDEA as well as asymmetric algorithms like RSA and Diffie-Hellman. The performance is evaluated based on parameters like encryption/decryption time, memory usage and throughput. Experiments show that Blowfish has better performance than AES for encrypting audio files, with lower average encryption and decryption times. In conclusion, cryptography is important for network security and Blowfish performs encryption/decryption more efficiently than AES for audio files.
Principles of public key cryptography and its UsesMohsin Ali
This document discusses the principles of public key cryptography. It begins by defining asymmetric encryption and how it uses a public key and private key instead of a single shared key. It then discusses key concepts like digital certificates and public key infrastructure. The document also provides examples of how public key cryptography can be used, including the RSA algorithm and key distribution methods like public key directories and certificates. It explains how public key cryptography solves the key distribution problem present in symmetric encryption.
What is cryptography,its types,two algorithms i.e RSA and DES.
explained well and referenced the slide share too to give more precise presentation. Thank you.
AES (Advanced Encryption Standard) is a symmetric block cipher algorithm that was adopted as a replacement for the DES (Data Encryption Standard) algorithm. AES is considered more secure than DES due to using a larger key size and being more computationally difficult to break. While AES is fast and reliable for encrypting files and documents, it is not suitable for encrypting communications due to the key exchange problem - for that, an asymmetric algorithm like RSA is typically used to securely exchange the AES key.
Twenty years of attacks on the rsa cryptosystemlinzi320
- The document surveys various attacks on the RSA cryptosystem over the past 20 years.
- It describes some elementary attacks, such as using a common modulus for multiple users or blinding signatures, which illustrate improper implementations of RSA.
- It also summarizes Wiener's 1994 attack, which shows that if the private exponent d is too small (less than N1/4), it can be efficiently recovered, breaking the system. The attack uses continued fraction approximations to recover d.
Cryptography is the art and science of securing communication and information by encrypting and decrypting data. It allows for secure transmission of data through both symmetric and asymmetric encryption methods as well as ensuring the integrity, confidentiality and authenticity of digital information. Modern cryptography plays a crucial role in network security through protocols like SSL/TLS that protect internet communication and transactions.
This document provides an overview of data encryption. It defines encryption as disguising information so that only those with the key can recover it. Encryption involves encrypting cleartext into ciphertext using an encryption key. Symmetric encryption uses the same key for encryption and decryption, while asymmetric encryption uses different keys. Encryption methods include transposition, which rearranges bits or characters, and substitution, which replaces them. The document discusses the Data Encryption Standard (DES) and RSA public key cryptosystem algorithms. It concludes that public key encryption can provide both privacy and authentication.
This document summarizes a talk on proxy cryptography given by Anca-Andreea Ivan and Yevgeniy Dodis at NDSS 2003. It introduces the problem of allowing one party (Bob) to decrypt ciphertexts or sign messages on behalf of another party (Alice) without knowing Alice's secret key. This is achieved using a third party (Escrow) and proxy functions. The talk aims to formally define proxy functions and construct simple schemes satisfying the definitions. It outlines related work and compares the authors' formal approach to previous work. It then defines unidirectional and bidirectional proxy functions for both encryption and signatures and presents generic and specialized constructions satisfying security definitions.
A 2,000-BIT MESSAGE IS USED TO GENERATE A 256-BIT HASH. ONE THE AVERAGE, HOW ...SophiaMorgans
1. The document provides 20 questions related to cryptography concepts such as hash functions, encryption algorithms (RSA, DES, 3DES), and digital signatures.
2. Questions cover topics like determining the key length needed to increase cracking time for a brute force attack, using asymmetric encryption to provide a digital signature, and comparing symmetric and asymmetric encryption algorithms.
3. Answers require applying mathematical and conceptual knowledge of cryptography standards and best practices.
The document discusses various topics related to security in e-commerce including cryptography mechanisms like symmetric and asymmetric encryption, hashing functions, and encryption algorithms like DES, AES, and RSA. It also covers security protocols like SSL/TLS, SET, S/MIME, and SSH. IPSec and its components AH, ESP and IKE are explained. The IKE phases including phase 1 for mutual authentication and phase 2 for establishing session keys are summarized.
Introduction to and survey of TLS security (BsidesHH 2014)Aaron Zauner
This document provides an introduction and survey of Transport Layer Security (TLS). It begins with motivations for studying TLS and provides background information on topics like cryptography, the TLS handshake process, and cipher suites. The document then discusses the history of TLS and examples of attacks against it. It aims to educate about TLS security and the ongoing efforts by the Internet Engineering Task Force (IETF) to improve TLS mitigations against modern threats.
1) O documento discute as mudanças necessárias na educação para se adaptar à sociedade mais interconectada, com foco na flexibilidade e na integração das novas tecnologias.
2) As dificuldades para a mudança na educação incluem desigualdades, falta de modelos avançados e contradições entre teoria e prática.
3) É necessário que educadores, administradores e alunos estejam abertos à mudança para que ela ocorra de forma efetiva.
Este documento describe los conceptos de presupuesto, plan de compras y presupuesto de materiales. Explica que un presupuesto es un plan financiero que estima los ingresos y gastos de una empresa para un período determinado, con el objetivo de planificar y controlar las actividades y resultados. El presupuesto de materiales estima las cantidades de materia prima necesarias para la producción, mientras que el plan de compras programa la adquisición de dichos materiales. Un buen presupuesto y plan de compras permite asegurar el abastecimiento oportuno de mater
Este documento proporciona un plan de estudios detallado para una asignatura que incluye 5 unidades de contenido, actividades de aprendizaje intra y extraclase, evaluaciones parciales, un examen final y un proyecto final. Además, incluye secciones sobre la universidad, el autor, el currículo, diarios metacognitivos y una bibliografía.
El pensamiento lógico-matemático se refiere al razonamiento deductivo y la capacidad de inferir nuevas proposiciones a partir de las conocidas usando reglas lógicas. La inteligencia lógico-matemática incluye habilidades como el cálculo matemático, el pensamiento numérico y la solución de problemas abstractos. Según Piaget, el pensamiento lógico del niño evoluciona de las funciones básicas de clasificación hacia la abstracción a medida que se desarrollan estructuras cognit
Financial statement analysis involves assessing a firm's past, present, and future financial conditions to identify strengths and weaknesses. Key tools include financial statements and ratio analysis, which standardizes information for comparisons of performance over time, against peers, and to industry standards. Ratio analysis is used for tasks like evaluating loan applications, creditworthiness, mergers, and investment opportunities. Ratios measure liquidity, leverage, activity/efficiency, and profitability.
buenos dias el trabajo q era para el dia de hoy.......mary taipe
El documento describe las características y funciones de los sistemas operativos. Un sistema operativo es el programa más importante de una computadora que provee una interfaz entre los programas, dispositivos hardware y el usuario. Los sistemas operativos realizan tareas básicas como administrar recursos, coordinar hardware y organizar archivos.
El documento describe las competencias matemáticas requeridas para resolver problemas. Define competencia como la capacidad de aplicar conocimientos en contextos reales de manera creativa y flexible. Explica que las competencias matemáticas incluyen pensar lógicamente, comunicar, modelar, plantear y resolver problemas, y usar herramientas matemáticas. Además, identifica ocho competencias específicas como pensar críticamente, argumentar, comunicar, modelar, resolver problemas, representar, usar lenguaje simbólico y herramientas.
La normalización es un proceso para organizar los datos en una base de datos relacional de manera que se minimicen la redundancia y dependencia de los datos. Existen tres formas normales principales: la primera forma normal elimina columnas repetidas, la segunda forma normal elimina dependencias parciales, y la tercera forma normal elimina datos que no dependen de la clave principal. Siguiendo este proceso de normalización, los datos se organizan de manera más eficiente y lógica en la base de datos.
El documento habla sobre los recursos humanos y su función dentro de las organizaciones. Explica que los recursos humanos se refieren al conjunto de empleados y su trabajo, pero también a la función que se encarga de la selección, contratación, formación y retención del personal. Esta función busca alinear las políticas de recursos humanos con la estrategia de la organización para implementarla a través de las personas. Generalmente incluye áreas como reclutamiento, capacitación, inducción y retención del personal.
El documento describe el entorno turístico, incluyendo la evolución histórica del turismo desde la antigüedad hasta la era contemporánea, los países más visitados, los elementos clave del turismo como la demanda, la oferta y los operadores turísticos. También cubre el paradigma de la sostenibilidad turística, las tres pilares de la sostenibilidad (económico, social y ambiental), las diferentes clases de turismo, y la normatividad turística en Colombia.
El documento presenta el plan de clases para una unidad sobre reacciones químicas. La unidad cubrirá diferentes tipos de reacciones químicas, sus características y fórmulas. El plan incluye expectativas de aprendizaje, temas, estrategias didácticas como presentaciones y debates en grupos, y una evaluación basada en el cumplimiento de las expectativas.
El documento resume las principales teorías sobre la naturaleza de la luz desde la antigüedad hasta el siglo XX. Comenzó con las teorías corpuscular y ondulatoria en los siglos XVII-XVIII, continuó con las teorías electromagnéticas y cuánticas en los siglos XIX-XX, y culminó con la mecánica ondulatoria que unificó las perspectivas corpuscular y ondulatoria.
El documento resume las principales teorías sobre la naturaleza de la luz desde la antigüedad hasta el siglo XX. Comenzó con las teorías corpuscular y ondulatoria en los siglos XVII-XVIII, continuó con las teorías electromagnéticas y de cuantos en los siglos XIX-XX, y culminó con la mecánica ondulatoria que unificó las perspectivas corpuscular y ondulatoria.
El documento describe tres formas en que se transmite el calor: conducción, convección y radiación. La conducción ocurre en sólidos en contacto, la convección ocurre en fluidos, y la radiación ocurre a través del espacio vacío entre cuerpos. El documento también describe experimentos que ilustran estas tres formas de transferencia de calor.
Este documento resume diferentes tipologías de redes. Describe las topologías de bus, anillo, estrella, árbol, malla y híbridas, explicando sus ventajas y desventajas. También explica mecanismos para la resolución de conflictos como CSMA/CD utilizados en algunas de estas topologías.
1) As empresas reconhecem que não podem apelar para todos os compradores e devem identificar quais segmentos podem atender melhor e de forma mais lucrativa.
2) O posicionamento do produto é como ele é definido pelos consumidores em relação aos seus atributos importantes e em relação aos produtos concorrentes.
3) A segmentação de mercado é essencial para que as empresas criem produtos para cada mercado-alvo e ajustem preços, distribuição e marketing de forma eficiente.
Este documento presenta información sobre las lesiones de los tejidos blandos. Describe las funciones de la piel y su estructura, así como diferentes tipos de lesiones cerradas y abiertas de los tejidos blandos como contusiones, hematomas, laceraciones, amputaciones y más. También detalla la evaluación y el tratamiento de emergencia para este tipo de lesiones, incluida la estabilización, control de sangrado, prevención de infecciones y transporte al hospital.
La normalización de esquemas de bases de datos relacionales sigue tres formas normales básicas. La primera forma normal elimina columnas repetidas. La segunda forma normal requiere que todas las columnas no clave dependan completamente de la clave primaria. La tercera forma normal elimina cualquier dependencia transitiva entre columnas no clave. Juntas, estas tres formas normales producen esquemas de bases de datos más simples, cohesivos y flexibles.
Module 6
Advanced Networking
Security problems with internet architecture, Introduction to Software defined networking, Working of SDN, SDN in data centre, SDN applications, Data centre networking, IoT.
This document discusses network security concepts including encryption, authentication, and threats. It introduces common network security scenarios involving friends (Alice and Bob) communicating securely while an intruder (Trudy) may intercept or alter messages. Examples of real systems that require security are also given such as web browsers, online banking, and network routers. Common network attacks are then outlined like eavesdropping, spoofing, and denial of service attacks. The document proceeds to explain approaches to network security including symmetric and public key encryption methods. Specific encryption algorithms are described like DES and RSA public key encryption.
The document discusses network security and introduces concepts like cryptography, authentication, and message integrity. It notes that network security aims to ensure confidentiality, authentication, and access for legitimate users while preventing attacks from unauthorized parties. The chapter will cover principles of cryptography, security protocols for different layers, and operational security measures like firewalls and intrusion detection systems. Users are asked to cite the source if using the slides and to respect the authors' copyright.
This document discusses the use and sharing of PowerPoint slides from a textbook on computer networking. It allows the slides to be modified and used for educational purposes with only two requirements: 1) Cite the source if using the slides substantially unaltered, and 2) Note the copyright if posting slides substantially unaltered online. The document is copyrighted by the authors of the textbook from 1996-2007.
The document discusses network security and introduces concepts like cryptography, authentication, and message integrity. It notes that network security aims to ensure confidentiality, authentication, and access to services. Cryptography uses techniques like encryption, digital signatures, and hash functions to provide these security properties. The document provides examples to illustrate symmetric and public key cryptography, including how algorithms like DES, AES, RSA and hash functions work. It also introduces common network security examples like Alice, Bob and the intruder Trudy.
This document discusses public key cryptography and the RSA algorithm. RSA allows two parties to communicate securely without having to share a secret key beforehand. It works by having each party generate both a public and private key. The public key can be used to encrypt messages, while only the private key can decrypt them. RSA relies on the difficulty of factoring large numbers to be secure. The document provides an example of how RSA key generation and encryption/decryption work in practice.
This document provides an overview of network security principles including cryptography, authentication, message integrity, and key distribution. It begins with an introduction to network security concepts and then outlines the topics that will be covered, which include principles of cryptography, authentication, integrity, key distribution, access control using firewalls, common attacks, and security at different layers. Examples are provided to illustrate authentication protocols and their vulnerabilities. Digital signatures and message digests are introduced as techniques for authentication and integrity. Symmetric and public key encryption algorithms like DES, AES, RSA are briefly described. The need for trusted intermediaries like key distribution centers and certification authorities is also noted.
The document discusses authentication protocols to securely prove identity between two parties communicating over a network. Protocol ap5.0 uses public key cryptography and a nonce (random number) to authenticate, but it is vulnerable to a man-in-the-middle attack where an attacker can pose as both parties to intercept and alter communications. The document explores several authentication protocols and their vulnerabilities to illustrate challenges in securely authenticating identities over an open network.
This document provides an introduction to security and cryptography. It begins with an overview of security goals like confidentiality, authenticity, integrity, and non-repudiation. It then discusses symmetric cryptography algorithms like DES and AES, and how they provide confidentiality. Asymmetric cryptography algorithms like RSA and ECC are introduced for providing authentication, non-repudiation through digital signatures, and facilitating key exchange. Hash functions are described for providing integrity and digital signatures. Modes of operation for block ciphers like CBC are covered. Popular algorithms and their application to security goals are summarized.
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography help achieve them.
- Symmetric cryptography algorithms like DES, Triple DES, and AES as well as modes of operation like CBC.
- Asymmetric cryptography concepts like public/private key pairs, digital signatures, and how RSA works.
- Other cryptographic tools like hash functions, message authentication codes, and key exchange methods like Diffie-Hellman.
- The role of public key infrastructure and certificates in authenticating public keys.
- Attacks on cryptographic algorithms and their implementations are also briefly discussed.
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography help achieve them.
- Symmetric cryptography algorithms like DES, Triple DES, and AES along with modes of operation like CBC.
- Asymmetric cryptography including key exchange with Diffie-Hellman and digital signatures with RSA and ECC.
- Cryptographic hash functions like SHA and their properties. Message authentication codes (MACs) that provide integrity.
- Public key infrastructure with certificates and how they establish authenticity of public keys.
- Attacks on algorithms, implementations, and protocols and the need for unpredictable
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography help achieve them.
- Symmetric cryptography algorithms like DES, Triple DES, and AES and how they operate using symmetric keys for encryption and decryption.
- Cryptographic hashing and message authentication codes (MACs) and how they provide integrity and authentication.
- Asymmetric (public key) cryptography like RSA and ECC using key pairs for encryption, signatures, and key exchange without pre-shared secrets.
- Key exchange methods like Diffie-Hellman and how public key infrastructure (PKI) uses digital
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography, hashes, signatures, and MACs address them.
- Symmetric block ciphers like DES and AES including modes of operation like CBC.
- Asymmetric cryptography concepts like key exchange using Diffie-Hellman and digital signatures using RSA.
- Cryptographic hash functions like SHA and their properties.
- Public key infrastructure concepts like certificates and how they establish authenticity of public keys.
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography help achieve them.
- Symmetric cryptography algorithms like DES, Triple DES, and AES and how they operate using symmetric keys for encryption and decryption.
- Cryptographic hashing and message authentication codes (MACs) and how they provide integrity and authentication.
- Asymmetric (public key) cryptography like RSA and ECC using key pairs for encryption, signatures, and key exchange without pre-shared secrets.
- Key exchange methods like Diffie-Hellman and how public key infrastructure (PKI) uses digital
This document provides an overview of security and cryptography topics including:
- The basics of security including confidentiality, authenticity, integrity, and non-repudiation goals and how symmetric and asymmetric cryptography help achieve them.
- Symmetric cryptography algorithms like DES, Triple DES, and AES and how they operate using symmetric keys for encryption and decryption.
- Cryptographic hashing and message authentication codes (MACs) and how they provide integrity and authentication.
- Asymmetric (public key) cryptography like RSA and ECC using key pairs for encryption, signatures, and key exchange without pre-shared secrets.
- Key exchange methods like Diffie-Hellman and how public key infrastructure (PKI) uses digital
This document provides an introduction to symmetric and asymmetric cryptography. Symmetric cryptography uses the same key for encryption and decryption, while asymmetric cryptography uses public and private key pairs. Symmetric cryptography is faster but requires secure key exchange, while asymmetric cryptography allows secure communication between parties who have not previously shared a key. Examples of symmetric algorithms discussed include AES and DES, while asymmetric or public key cryptography is illustrated using Diffie-Hellman key exchange. Both types are still widely used with increasingly large key sizes providing greater security.
Symmetric encryption suffers from several key distribution and management problems in modern distributed communication environments. Asymmetric encryption solves these issues by using public/private key pairs, allowing anyone to encrypt messages using the public key but only the private key holder can decrypt. Digital signatures, key certification through public key infrastructure (PKI), and hash functions are important applications of asymmetric cryptography.
The document discusses network security and begins by noting that the slides can be freely used and modified if their source is mentioned. It then provides an overview of the goals and roadmap for Chapter 8, which covers principles of cryptography, message integrity, securing various network layers, firewalls, and intrusion detection systems. The chapter aims to explain the fundamentals of network security and how security is implemented in practice.
Asymmetric key cryptography uses two keys - a public key that can be shared publicly and a private key that is kept secret. This allows two parties who have never shared secrets before, like Alice and Bob, to communicate securely by encrypting messages with each other's public keys. Common asymmetric algorithms discussed are RSA, which uses prime number factorization, and ECC, which is based on elliptic curve discrete logarithms. A public key infrastructure (PKI) with certificate authorities (CAs) is required to authenticate users and manage public keys.
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International Upcycling Research Network advisory board meeting 4Kyungeun Sung
Slides used for the International Upcycling Research Network advisory board 4 (last one). The project is based at De Montfort University in Leicester, UK, and funded by the Arts and Humanities Research Council.
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1. Chapter 8
Network Security
A note on the use of these ppt slides:
We’re making these slides freely available to all (faculty, students, readers). Computer Networking:
They’re in powerpoint form so you can add, modify, and delete slides
(including this one) and slide content to suit your needs. They obviously A Top Down Approach
represent a lot of work on our part. In return for use, we only ask the Featuring the Internet,
following:
If you use these slides (e.g., in a class) in substantially unaltered form,
that you mention their source (after all, we’d like people to use our book!) 2nd edition.
If you post any slides in substantially unaltered form on a www site, that
you note that they are adapted from (or perhaps identical to) our slides, and Jim Kurose, Keith Ross
note our copyright of this material. Addison-Wesley, July
Thanks and enjoy! JFK/KWR 2002.
All material copyright 1996-2002
J.F Kurose and K.W. Ross, All Rights Reserved
Network Security 7-1
2. Chapter 7: Network Security
Chapter goals:
Ì understand principles of network security:
r cryptography and its many uses beyond
“confidentiality”
r authentication
r message integrity
r key distribution
Ì security in practice:
r firewalls
r security in application, transport, network, link
layers
Network Security 7-2
3. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-3
4. What is network security?
Confidentiality: only sender, intended receiver
should “understand” message contents
r sender encrypts message
r receiver decrypts message
Authentication: sender, receiver want to confirm
identity of each other
Message Integrity: sender, receiver want to ensure
message not altered (in transit, or afterwards)
without detection
Access and Availability: services must be accessible
and available to users
Network Security 7-4
5. Friends and enemies: Alice, Bob, Trudy
Ì well-known in network security world
Ì Bob, Alice (lovers!) want to communicate “securely”
Ì Trudy (intruder) may intercept, delete, add messages
Alice Bob
data, control
channel
messages
data secure secure data
sender receiver
Trudy
Network Security 7-5
6. Who might Bob, Alice be?
Ì … well, real-life Bobs and Alices!
Ì Web browser/server for electronic
transactions (e.g., on-line purchases)
Ì on-line banking client/server
Ì DNS servers
Ì routers exchanging routing table updates
Ì other examples?
Network Security 7-6
7. There are bad guys (and girls) out there!
Q: What can a “bad guy” do?
A: a lot!
r eavesdrop: intercept messages
r actively insert messages into connection
r impersonation: can fake (spoof) source address
in packet (or any field in packet)
r hijacking: “take over” ongoing connection by
removing sender or receiver, inserting himself
in place
r denial of service: prevent service from being
used by others (e.g., by overloading resources)
more on this later ……
Network Security 7-7
8. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-8
9. The language of cryptography
Alice’s Bob’s
K encryption K decryption
A
key B key
plaintext encryption ciphertext decryption plaintext
algorithm algorithm
symmetric key crypto: sender, receiver keys identical
public-key crypto: encryption key public, decryption key
secret (private)
Network Security 7-9
10. Symmetric key cryptography
substitution cipher: substituting one thing for another
r monoalphabetic cipher: substitute one letter for another
plaintext: abcdefghijklmnopqrstuvwxyz
ciphertext: mnbvcxzasdfghjklpoiuytrewq
E.g.: Plaintext: bob. i love you. alice
ciphertext: nkn. s gktc wky. mgsbc
Q: How hard to break this simple cipher?:
brute force (how hard?)
other?
Network Security 7-10
11. Symmetric key cryptography
KA-B KA-B
plaintext encryption ciphertext decryption plaintext
message, m algorithm algorithm
K (m)
A-B
m=K ( K (m) )
A-B A-B
symmetric key crypto: Bob and Alice share know same
(symmetric) key: K
A-B
Ì e.g., key is knowing substitution pattern in mono
alphabetic substitution cipher
Ì Q: how do Bob and Alice agree on key value?
Network Security 7-11
12. Symmetric key crypto: DES
DES: Data Encryption Standard
Ì US encryption standard [NIST 1993]
Ì 56-bit symmetric key, 64-bit plaintext input
Ì How secure is DES?
rDES Challenge: 56-bit-key-encrypted phrase
(“Strong cryptography makes the world a safer
place”) decrypted (brute force) in 4 months
r no known “backdoor” decryption approach
Ì making DES more secure:
r use three keys sequentially (3-DES) on each datum
r use cipher-block chaining
Network Security 7-12
13. Symmetric key
crypto: DES
DES operation
initial permutation
16 identical “rounds” of
function application,
each using different
48 bits of key
final permutation
Network Security 7-13
14. AES: Advanced Encryption Standard
Ì new (Nov. 2001) symmetric-key NIST
standard, replacing DES
Ì processes data in 128 bit blocks
Ì 128, 192, or 256 bit keys
Ì brute force decryption (try each key)
taking 1 sec on DES, takes 149 trillion
years for AES
Network Security 7-14
15. Public Key Cryptography
symmetric key crypto public key cryptography
Ì requires sender, Ì radically different
receiver know shared approach [Diffie-
secret key Hellman76, RSA78]
Ì Q: how to agree on key Ì sender, receiver do
in first place not share secret key
(particularly if never Ì public encryption key
“met”)? known to all
Ì private decryption
key known only to
receiver
Network Security 7-15
16. Public key cryptography
+ Bob’s public
K
B key
- Bob’s private
K
B key
plaintext encryption ciphertext decryption plaintext
message, m algorithm + algorithm message
K (m) - +
B m = K B(K (m))
B
Network Security 7-16
17. Public key encryption algorithms
Requirements:
+ . .
1 need K B( ) and K - ( ) such that
B
- +
K (K (m)) = m
B B
+
2 given public key KB , it should be
impossible to compute private
-
key K B
RSA: Rivest, Shamir, Adelson algorithm
Network Security 7-17
18. RSA: Choosing keys
1. Choose two large prime numbers p, q.
(e.g., 1024 bits each)
2. Compute n = pq, z = (p-1)(q-1)
3. Choose e (with e<n) that has no common factors
with z. (e, z are “relatively prime”).
4. Choose d such that ed-1 is exactly divisible by z.
(in other words: ed mod z = 1 ).
5. Public key is (n,e). Private key is (n,d).
+ -
KB KB
Network Security 7-18
19. RSA: Encryption, decryption
0. Given (n,e) and (n,d) as computed above
1. To encrypt bit pattern, m, compute
e
c = m e mod n (i.e., remainder when m is divided by n)
2. To decrypt received bit pattern, c, compute
d
m = c d mod n (i.e., remainder when c is divided by n)
Magic d
m = (m e mod n) mod n
happens!
c
Network Security 7-19
20. RSA example:
Bob chooses p=5, q=7. Then n=35, z=24.
e=5 (so e, z relatively prime).
d=29 (so ed-1 exactly divisible by z.
letter m me c = me mod n
encrypt:
l 12 1524832 17
d
decrypt:
c c m = cd mod n letter
17 481968572106750915091411825223071697 12 l
Network Security 7-20
21. RSA: Why is that d
m = (m e mod n) mod n
Useful number theory result: If p,q prime and
n = pq, then: y y mod (p-1)(q-1)
x mod n = x mod n
e
(m mod n) d mod n = med mod n
ed mod (p-1)(q-1)
= m mod n
(using number theory result above)
1
= m mod n
(since we chose ed to be divisible by
(p-1)(q-1) with remainder 1 )
= m
Network Security 7-21
22. RSA: another important property
The following property will be very useful later:
- + + -
K (K (m)) = m = K (K (m))
B B B B
use public key use private key
first, followed first, followed
by private key by public key
Result is the same!
Network Security 7-22
23. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-23
24. Authentication
Goal: Bob wants Alice to “prove” her identity
to him
Protocol ap1.0: Alice says “I am Alice”
“I am Alice”
Failure scenario??
Network Security 7-24
25. Authentication
Goal: Bob wants Alice to “prove” her identity
to him
Protocol ap1.0: Alice says “I am Alice”
in a network,
Bob can not “see”
Alice, so Trudy simply
“I am Alice” declares
herself to be Alice
Network Security 7-25
26. Authentication: another try
Protocol ap2.0: Alice says “I am Alice” in an IP packet
containing her source IP address
Alice’s
IP address
“I am Alice”
Failure scenario??
Network Security 7-26
27. Authentication: another try
Protocol ap2.0: Alice says “I am Alice” in an IP packet
containing her source IP address
Trudy can create
a packet
Alice’s
“spoofing”
IP address
“I am Alice” Alice’s address
Network Security 7-27
28. Authentication: another try
Protocol ap3.0: Alice says “I am Alice” and sends her
secret password to “prove” it.
Alice’s Alice’s
“I’m Alice”
IP addr password
Alice’s Failure scenario??
OK
IP addr
Network Security 7-28
29. Authentication: another try
Protocol ap3.0: Alice says “I am Alice” and sends her
secret password to “prove” it.
Alice’s Alice’s
“I’m Alice”
IP addr password
playback attack: Trudy
Alice’s records Alice’s packet
OK
IP addr and later
plays it back to Bob
Alice’s Alice’s
“I’m Alice”
IP addr password
Network Security 7-29
30. Authentication: yet another try
Protocol ap3.1: Alice says “I am Alice” and sends her
encrypted secret password to “prove” it.
Alice’s encrypted
“I’m Alice”
IP addr password
Alice’s Failure scenario??
OK
IP addr
Network Security 7-30
31. Authentication: another try
Protocol ap3.1: Alice says “I am Alice” and sends her
encrypted secret password to “prove” it.
Alice’s encryppted
IP addr password
“I’m Alice” record
and
Alice’s
OK playback
IP addr
still works!
Alice’s encrypted
“I’m Alice”
IP addr password
Network Security 7-31
32. Authentication: yet another try
Goal: avoid playback attack
Nonce: number (R) used only once –in-a-lifetime
ap4.0: to prove Alice “live”, Bob sends Alice nonce, R.
Alice
must return R, encrypted with shared secret key
“I am Alice”
R
KA-B(R) Alice is live, and
only Alice knows
key to encrypt
nonce, so it must
Failures, drawbacks? be Alice!
Network Security 7-32
33. Authentication: ap5.0
ap4.0 requires shared symmetric key
Ì can we authenticate using public key techniques?
ap5.0: use nonce, public key cryptography
“I am Alice”
Bob computes
R + -
- KA(KA (R)) = R
K A (R) and knows only Alice
“send me your public key”
could have the private
+ key, that encrypted R
KA such that
+ -
K (K (R)) = R
A A
Network Security 7-33
34. ap5.0: security hole
Man (woman) in the middle attack: Trudy poses as
Alice (to Bob) and as Bob (to Alice)
I am Alice I am Alice
R -
K (R)
T
R - Send me your public key
K (R) +
A K
T
Send me your public key
+
K
A +
K (m)
Trudy gets T
- +
+ m = K (K (m))
K (m)
A sends T to Alice
m T
- + ennrypted with
m = K (K (m))
A A Alice’s public key
Network Security 7-34
35. ap5.0: security hole
Man (woman) in the middle attack: Trudy poses as
Alice (to Bob) and as Bob (to Alice)
Difficult to detect:
Bob receives everything that Alice sends, and vice
versa. (e.g., so Bob, Alice can meet one week later and
recall conversation)
problem is that Trudy receives all messages as well!
Network Security 7-35
36. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Message integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-36
37. Digital Signatures
Cryptographic technique analogous to hand-
written signatures.
Ì sender (Bob) digitally signs document,
establishing he is document owner/creator.
Ì verifiable, nonforgeable: recipient (Alice) can
prove to someone that Bob, and no one else
(including Alice), must have signed document
Network Security 7-37
38. Digital Signatures
Simple digital signature for message m:
Ì Bob signs m by encrypting with his private key
- -
KB, creating “signed” message, KB(m)
-
Bob’s message, m K B Bob’s private -
K B(m)
key
Dear Alice
Bob’s message,
Oh, how I have missed Public key m, signed
you. I think of you all the
time! …(blah blah blah) encryption (encrypted) with
algorithm his private key
Bob
Network Security 7-38
39. Digital Signatures (more)
-
Ì Suppose Alice receives msg m, digital signature KB(m)
Ì Alice verifies m signed by Bob by applying Bob’s
+ - + -
public key KB to KB(m) then checks KB(KB(m) ) = m.
+ -
Ì If KB(KB(m) ) = m, whoever signed m must have used
Bob’s private key.
Alice thus verifies that:
½ Bob signed m.
½ No one else signed m.
½ Bob signed m and not m’.
Non-repudiation:
-
Alice can take m, and signature KB(m) to
court and prove that Bob signed m.
Network Security 7-39
40. Message Digests large
H: Hash
message
Function
m
Computationally expensive
to public-key-encrypt
H(m)
long messages
Goal: fixed-length, easy- Hash function properties:
to-compute digital Ì many-to-1
“fingerprint”
Ì produces fixed-size msg
Ì apply hash function H
digest (fingerprint)
to m, get fixed size
Ì given message digest x,
message digest, H(m).
computationally
infeasible to find m such
that x = H(m)
Network Security 7-40
41. Internet checksum: poor crypto hash
function
Internet checksum has some properties of hash function:
½ produces fixed length digest (16-bit sum) of message
½ is many-to-one
But given message with given hash value, it is easy to find
another message with same hash value:
message ASCII format message ASCII format
I O U 1 49 4F 55 31 I O U 9 49 4F 55 39
0 0 . 9 30 30 2E 39 0 0 . 1 30 30 2E 31
9 B O B 39 42 D2 42 9 B O B 39 42 D2 42
B2 C1 D2 AC different messages B2 C1 D2 AC
but identical checksums!
Network Security 7-41
42. Digital signature = signed message digest
Alice verifies signature and
Bob sends digitally signed integrity of digitally signed
message: message:
large
message H: Hash encrypted
m function H(m)
msg digest
-
KB(H(m))
Bob’s digital large
private signature message
- Bob’s
key KB (encrypt) m digital
public
+ signature
key KB
encrypted H: Hash (decrypt)
msg digest function
-
+ KB(H(m))
H(m) H(m)
equal
?
Network Security 7-42
43. Hash Function Algorithms
Ì MD5 hash function widely used (RFC 1321)
r computes 128-bit message digest in 4-step
process.
r arbitrary 128-bit string x, appears difficult to
construct msg m whose MD5 hash is equal to x.
Ì SHA-1 is also used.
r US standard [NIST, FIPS PUB 180-1]
r 160-bit message digest
Network Security 7-43
44. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-44
45. Trusted Intermediaries
Symmetric key problem: Public key problem:
Ì How do two entities Ì When Alice obtains
establish shared secret Bob’s public key (from
key over network? web site, e-mail,
Solution: diskette), how does she
know it is Bob’s public
Ì trusted key distribution
key, not Trudy’s?
center (KDC) acting as
intermediary between Solution:
entities Ì trusted certification
authority (CA)
Network Security 7-45
46. Key Distribution Center (KDC)
Ì Alice, Bob need shared symmetric key.
Ì KDC: server shares different secret key with each
registered user (many users)
Ì Alice, Bob know own symmetric keys, KA-KDC KB-KDC , for
communicating with KDC.
KDC
KA-KDC KP-KDC
KX-KDC
KP-KDC KB-KDC
KY-KDC
KZ-KDC
KA-KDC KB-KDC
Network Security 7-46
47. Key Distribution Center (KDC)
Q: How does KDC allow Bob, Alice to determine shared
symmetric secret key to communicate with each other?
KDC
generates
KA-KDC(A,B)
R1
Alice KA-KDC(R1, KB-KDC(A,R1) )
Bob knows to
knows use R1 to
R1 KB-KDC(A,R1) communicate
with Alice
Alice and Bob communicate: using R1 as
session key for shared symmetric encryption
Network Security 7-47
48. Certification Authorities
Ì Certification authority (CA): binds public key to
particular entity, E.
Ì E (person, router) registers its public key with CA.
r E provides “proof of identity” to CA.
r CA creates certificate binding E to its public key.
r certificate containing E’s public key digitally signed by CA
– CA says “this is E’s public key”
Bob’s digital
+
public +
signature KB
key KB (encrypt)
CA
certificate for
K-
Bob’s private
identifying key CA Bob’s public key,
information signed by CA
Network Security 7-48
49. Certification Authorities
Ì When Alice wants Bob’s public key:
r gets Bob’s certificate (Bob or elsewhere).
r apply CA’s public key to Bob’s certificate, get
Bob’s public key
+ digital Bob’s
KB signature public
+
(decrypt) K B key
CA
public +
K CA
key
Network Security 7-49
50. A certificate contains:
Ì Serial number (unique to issuer)
Ì info about certificate owner, including algorithm
and key value itself (not shown)
Ì info about
certificate
issuer
Ì valid dates
Ì digital
signature by
issuer
Network Security 7-50
51. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-51
53. Firewalls: Why
prevent denial of service attacks:
r SYN flooding: attacker establishes many bogus
TCP connections, no resources left for “real”
connections.
prevent illegal modification/access of internal data.
r e.g., attacker replaces CIA’s homepage with
something else
allow only authorized access to inside network (set of
authenticated users/hosts)
two types of firewalls:
r application-level
r packet-filtering
Network Security 7-53
54. Should arriving
Packet Filtering packet be allowed
in? Departing packet
let out?
Ì internal network connected to Internet via
router firewall
Ì router filters packet-by-packet, decision to
forward/drop packet based on:
r source IP address, destination IP address
r TCP/UDP source and destination port numbers
r ICMP message type
r TCP SYN and ACK bits
Network Security 7-54
55. Packet Filtering
Ì Example 1: block incoming and outgoing
datagrams with IP protocol field = 17 and with
either source or dest port = 23.
r All incoming and outgoing UDP flows and telnet
connections are blocked.
Ì Example 2: Block inbound TCP segments with
ACK=0.
r Prevents external clients from making TCP
connections with internal clients, but allows
internal clients to connect to outside.
Network Security 7-55
56. Application gateways gateway-to-remote
host telnet session
host-to-gateway
telnet session
Ì Filters packets on
application data as well application
gateway
router and filter
as on IP/TCP/UDP fields.
Ì Example: allow select
internal users to telnet
outside.
1. Require all telnet users to telnet through gateway.
2. For authorized users, gateway sets up telnet connection to
dest host. Gateway relays data between 2 connections
3. Router filter blocks all telnet connections not originating
from gateway.
Network Security 7-56
57. Limitations of firewalls and gateways
Ì IP spoofing: router Ì filters often use all or
can’t know if data nothing policy for UDP.
“really” comes from Ì tradeoff: degree of
claimed source communication with
Ì if multiple app’s. need outside world, level of
special treatment, each security
has own app. gateway. Ì many highly protected
Ì client software must sites still suffer from
know how to contact attacks.
gateway.
r e.g., must set IP address
of proxy in Web
browser
Network Security 7-57
58. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
Network Security 7-58
59. Internet security threats
Mapping:
r before attacking: “case the joint” – find out
what services are implemented on network
r Use ping to determine what hosts have
addresses on network
r Port-scanning: try to establish TCP connection
to each port in sequence (see what happens)
r nmap (http://www.insecure.org/nmap/) mapper:
“network exploration and security auditing”
Countermeasures?
Network Security 7-59
60. Internet security threats
Mapping: countermeasures
r record traffic entering network
r look for suspicious activity (IP addresses, pots
being scanned sequentially)
Network Security 7-60
61. Internet security threats
Packet sniffing:
r broadcast media
r promiscuous NIC reads all packets passing by
r can read all unencrypted data (e.g. passwords)
r e.g.: C sniffs B’s packets
A C
src:B dest:A payload
B
Countermeasures?
Network Security 7-61
62. Internet security threats
Packet sniffing: countermeasures
r all hosts in orgnization run software that
checks periodically if host interface in
promiscuous mode.
r one host per segment of broadcast media
(switched Ethernet at hub)
A C
src:B dest:A payload
B
Network Security 7-62
63. Internet security threats
IP Spoofing:
r can generate “raw” IP packets directly from
application, putting any value into IP source
address field
r receiver can’t tell if source is spoofed
r e.g.: C pretends to be B
A C
src:B dest:A payload
B
Countermeasures?
Network Security 7-63
64. Internet security threats
IP Spoofing: ingress filtering
r routers should not forward outgoing packets
with invalid source addresses (e.g., datagram
source address not in router’s network)
r great, but ingress filtering can not be mandated
for all networks
A C
src:B dest:A payload
B
Network Security 7-64
65. Internet security threats
Denial of service (DOS):
r flood of maliciously generated packets “swamp”
receiver
r Distributed DOS (DDOS): multiple coordinated
sources swamp receiver
r e.g., C and remote host SYN-attack A
A C
SYN
SYN
SYN SYN SYN
B
SYN
Countermeasures? SYN
Network Security 7-65
66. Internet security threats
Denial of service (DOS): countermeasures
r filter out flooded packets (e.g., SYN) before
reaaching host: throw out good with bad
r traceback to source of floods (most likely an
innocent, compromised machine)
A C
SYN
SYN
SYN SYN SYN
B
SYN
SYN
Network Security 7-66
67. Chapter 7 roadmap
7.1 What is network security?
7.2 Principles of cryptography
7.3 Authentication
7.4 Integrity
7.5 Key Distribution and certification
7.6 Access control: firewalls
7.7 Attacks and counter measures
7.8 Security in many layers
7.8.1. Secure email
7.8.2. Secure sockets
7.8.3. IPsec
8.8.4. 802.11 WEP
Network Security 7-67
68. Secure e-mail
Alice wants to send confidential e-mail, m, to Bob.
KS
m K (.
S )
KS(m ) KS(m )
KS( ) . m
+ Internet - KS
KS
+.
K ()
B + +
- .
KB ( )
KB(KS ) KB(KS )
+ -
KB
KB
Alice:
generates random symmetric private key, KS.
encrypts message with KS (for efficiency)
also encrypts KS with Bob’s public key.
sends both KS(m) and KB(KS) to Bob.
Network Security 7-68
69. Secure e-mail
Alice wants to send confidential e-mail, m, to Bob.
KS
m K (.
S )
KS(m ) KS(m )
KS( ) . m
+ Internet - KS
KS
+.
K ()
B + +
- .
KB ( )
KB(KS ) KB(KS )
+ -
KB
KB
Bob:
uses his private key to decrypt and recover KS
uses KS to decrypt KS(m) to recover m
Network Security 7-69
70. Secure e-mail (continued)
• Alice wants to provide sender authentication
message integrity.
- KA
+
KA
- -
m .
H( )
-.
K ()
A
KA(H(m)) KA(H(m)) +
KA ( )
. H(m )
+ Internet - compare
m H( ) . H(m )
m
• Alice digitally signs message.
• sends both message (in the clear) and digital signature.
Network Security 7-70
71. Secure e-mail (continued)
• Alice wants to provide secrecy, sender authentication,
message integrity.
-
KA
-
m .
H( )
- .
K A( )
KA(H(m))
KS
+ KS( ) .
m + Internet
KS
+
KB( )
. +
KB(KS )
+
KB
Alice uses three keys: her private key, Bob’s public
key, newly created symmetric key
Network Security 7-71
72. Pretty good privacy (PGP)
Ì Internet e-mail encryption A PGP signed message:
scheme, de-facto standard.
---BEGIN PGP SIGNED MESSAGE---
Ì uses symmetric key Hash: SHA1
cryptography, public key
cryptography, hash Bob:My husband is out of town
tonight.Passionately yours,
function, and digital Alice
signature as described.
Ì provides secrecy, sender ---BEGIN PGP SIGNATURE---
Version: PGP 5.0
authentication, integrity. Charset: noconv
Ì inventor, Phil Zimmerman, yhHJRHhGJGhgg/12EpJ+lo8gE4vB3mqJh
was target of 3-year FEvZP9t6n7G6m5Gw2
---END PGP SIGNATURE---
federal investigation.
Network Security 7-72
73. Secure sockets layer (SSL)
Ì transport layer Ì server authentication:
r SSL-enabled browser
security to any TCP- includes public keys for
based app using SSL trusted CAs.
services. r Browser requests
Ì used between Web server certificate,
issued by trusted CA.
browsers, servers for r Browser uses CA’s
e-commerce (shttp). public key to extract
Ì security services: server’s public key from
certificate.
r server authentication Ì check your browser’s
r data encryption security menu to see
r client authentication its trusted CAs.
(optional)
Network Security 7-73
74. SSL (continued)
Encrypted SSL session: Ì SSL: basis of IETF
Ì Browser generates Transport Layer
symmetric session key, Security (TLS).
encrypts it with server’s Ì SSL can be used for
public key, sends non-Web applications,
encrypted key to server. e.g., IMAP.
Ì Using private key, server Ì Client authentication
decrypts session key. can be done with client
Ì Browser, server know certificates.
session key
r All data sent into TCP
socket (by client or server)
encrypted with session key.
Network Security 7-74
75. IPsec: Network Layer Security
Ì Network-layer secrecy:
Ì For both AH and ESP, source,
r sending host encrypts the
destination handshake:
data in IP datagram
r create network-layer
r TCP and UDP segments;
logical channel called a
ICMP and SNMP
security association (SA)
messages.
Ì Each SA unidirectional.
Ì Network-layer authentication
Ì Uniquely determined by:
r destination host can
r security protocol (AH or
authenticate source IP
address ESP)
Ì Two principle protocols: r source IP address
r authentication header r 32-bit connection ID
(AH) protocol
r encapsulation security
payload (ESP) protocol
Network Security 7-75
76. Authentication Header (AH) Protocol
Ì provides source AH header includes:
authentication, data Ì connection identifier
integrity, no Ì authentication data:
confidentiality source- signed message
Ì AH header inserted digest calculated over
between IP header, original IP datagram.
data field. Ì next header field:
Ì protocol field: 51 specifies type of data
Ì intermediate routers (e.g., TCP, UDP, ICMP)
process datagrams as
usual
IP header AH header data (e.g., TCP, UDP segment)
Network Security 7-76
77. ESP Protocol
Ì provides secrecy, host Ì ESP authentication
authentication, data field is similar to AH
integrity. authentication field.
Ì data, ESP trailer Ì Protocol = 50.
encrypted.
Ì next header field is in ESP
trailer.
authenticated
encrypted
ESP ESP ESP
IP header TCP/UDP segment
header trailer authent.
Network Security 7-77
78. IEEE 802.11 security
Ì War-driving: drive around Bay area, see what 802.11
networks available?
r More than 9000 accessible from public roadways
r 85% use no encryption/authentication
r packet-sniffing and various attacks easy!
Ì Wired Equivalent Privacy (WEP): authentication as in
protocol ap4.0
r host requests authentication from access point
r access point sends 128 bit nonce
r host encrypts nonce using shared symmetric key
r access point decrypts nonce, authenticates host
Network Security 7-78
79. IEEE 802.11 security
Ì Wired Equivalent Privacy (WEP): data encryption
r Host/AP share 40 bit symmetric key (semi-
permanent)
r Host appends 24-bit initialization vector (IV) to
create 64-bit key
r 64 bit key used to generate stream of keys, kiIV
r kiIV used to encrypt ith byte, di, in frame:
ci = di XOR kiIV
r IV and encrypted bytes, ci sent in frame
Network Security 7-79
80. 802.11 WEP encryption
IV
(per frame)
KS: 40-bit key sequence generator
secret ( for given KS, IV)
symmetric
k1IV k2IV k3IV … kNIV kN+1IV… kN+1IV 802.11 WEP-encrypted data
key IV
header plus CRC
plaintext
frame data d1 d2 d3 … dN CRC1 … CRC4
plus CRC
c1 c2 c3 … cN cN+1 … cN+4
Sender-side WEP encryption
Figure 7.8-new1: 802.11 WEP protocol
Network Security 7-80
81. Breaking 802.11 WEP encryption
Security hole:
Ì 24-bit IV, one IV per frame, -> IV’s eventually reused
Ì IV transmitted in plaintext -> IV reuse detected
Ì Attack:
r Trudy causes Alice to encrypt known plaintext d1 d2
d3 d4 …
r Trudy sees: ci = di XOR kiIV
r Trudy knows ci di, so can compute kiIV
r Trudy knows encrypting key sequence k1IV k2IV k3IV …
r Next time IV is used, Trudy can decrypt!
Network Security 7-81
82. Network Security (summary)
Basic techniques…...
r cryptography (symmetric and public)
r authentication
r message integrity
r key distribution
…. used in many different security scenarios
r secure email
r secure transport (SSL)
r IP sec
r 802.11 WEP
Network Security 7-82