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 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.
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.
The document provides an overview of cryptography concepts including encryption, decryption, symmetric cryptosystems, block ciphers, substitution ciphers, the one-time pad, and algorithms such as DES, Triple DES, AES, and others. Key points covered include Kerckhoffs's principle of keeping algorithms public and keys private, how symmetric encryption works between two parties with a shared key, methods of encrypting plaintext in blocks or as a bit stream, techniques like substitution and transposition ciphers, weaknesses of approaches like the Hill cipher, and the history and operation of standard block ciphers.
1. The document discusses public-key cryptography and some of its key concepts like asymmetric encryption where each user has a public and private key.
2. It also covers applications like encryption, digital signatures, and key exchange. It notes that while public-key crypto has advantages, symmetric crypto is still important due to public-key crypto's lower speed.
3. The RSA algorithm is presented as one of the first implementations of public-key cryptography based on the difficulty of factoring large integers.
Cryptography is the science of keeping communications secure through various encryption techniques. There are two main types: symmetric encryption which uses a shared secret key for encryption and decryption, and asymmetric encryption which uses a public/private key pair. Symmetric encryption is faster but more difficult to implement for multiple parties, while asymmetric encryption using algorithms like RSA enables easy key distribution and digital signatures.
Generate an Encryption Key by using Biometric Cryptosystems to secure transfe...IOSR Journals
The document describes a proposed method for generating an encryption key from biometric cryptosystems to securely transfer data over a network. It involves extracting minutiae points from a fingerprint scan, generating a cryptographic key from the biometric template, and using an RSA encryption algorithm with the biometric-derived private key. A public key is also calculated based on ridge and furrow patterns in the fingerprint scan. The goal is to uniquely generate encryption keys for each individual using their biometric fingerprint information to add an extra layer of security beyond traditional encryption techniques.
This document provides an overview of cryptography concepts and algorithms. It discusses symmetric and asymmetric encryption algorithms such as DES, AES, RSA. It also covers hashing algorithms like MD5 and SHA which are used to generate cryptographic checksums of documents. The key ideas are that encryption encodes information, decryption decodes it, symmetric algorithms use the same key for both, and asymmetric algorithms use different public/private keys for encryption and decryption respectively.
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.
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.
The document provides an overview of cryptography concepts including encryption, decryption, symmetric cryptosystems, block ciphers, substitution ciphers, the one-time pad, and algorithms such as DES, Triple DES, AES, and others. Key points covered include Kerckhoffs's principle of keeping algorithms public and keys private, how symmetric encryption works between two parties with a shared key, methods of encrypting plaintext in blocks or as a bit stream, techniques like substitution and transposition ciphers, weaknesses of approaches like the Hill cipher, and the history and operation of standard block ciphers.
1. The document discusses public-key cryptography and some of its key concepts like asymmetric encryption where each user has a public and private key.
2. It also covers applications like encryption, digital signatures, and key exchange. It notes that while public-key crypto has advantages, symmetric crypto is still important due to public-key crypto's lower speed.
3. The RSA algorithm is presented as one of the first implementations of public-key cryptography based on the difficulty of factoring large integers.
Cryptography is the science of keeping communications secure through various encryption techniques. There are two main types: symmetric encryption which uses a shared secret key for encryption and decryption, and asymmetric encryption which uses a public/private key pair. Symmetric encryption is faster but more difficult to implement for multiple parties, while asymmetric encryption using algorithms like RSA enables easy key distribution and digital signatures.
Generate an Encryption Key by using Biometric Cryptosystems to secure transfe...IOSR Journals
The document describes a proposed method for generating an encryption key from biometric cryptosystems to securely transfer data over a network. It involves extracting minutiae points from a fingerprint scan, generating a cryptographic key from the biometric template, and using an RSA encryption algorithm with the biometric-derived private key. A public key is also calculated based on ridge and furrow patterns in the fingerprint scan. The goal is to uniquely generate encryption keys for each individual using their biometric fingerprint information to add an extra layer of security beyond traditional encryption techniques.
This document provides an overview of cryptography concepts and algorithms. It discusses symmetric and asymmetric encryption algorithms such as DES, AES, RSA. It also covers hashing algorithms like MD5 and SHA which are used to generate cryptographic checksums of documents. The key ideas are that encryption encodes information, decryption decodes it, symmetric algorithms use the same key for both, and asymmetric algorithms use different public/private keys for encryption and decryption respectively.
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.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Bluetooth technology is an emerging wireless networking standard, which is based on chip that provides short-range wireless frequency hopping communication. Now, Bluetooth technology is mainly applied to the communication between mobile terminal devices, such as palm computers, mobile phones, laptops and so on. However, the phenomenon of data-leaking frequently arises in using the Bluetooth technology for data transfer. To enhance the security of data transmission in Bluetooth communication, a hybrid encryption algorithm based on DES and RSA is proposed. The currently used encryption algorithm employed by the Bluetooth to protect the confidentiality of data during transport between two or more devices is a 128-bit symmetric stream cipher called E0. The proposed hybrid encryption algorithm, instead of the E0 encryption, DES algorithm is used for data transmission because of its higher efficiency in block encryption, and RSA algorithm is used for the encryption of the key of the DES because of its management advantages in key cipher. Under the dual protection with the DES algorithm and the RSA algorithm, the data transmission in the Bluetooth system will be more secure. This project is extended with triple des in place of des to enhance more security.
DES is a widely-used method of data encryption that uses a private key chosen from 72 quadrillion possible keys to encrypt 64-bit blocks of data using 16 rounds of operations. While DES is considered strong encryption, some use triple DES for additional security. In 1997, a cooperative effort of 14,000 computers broke a DES encrypted message by trying 18 quadrillion keys out of the 72 quadrillion possibilities. DES originated at IBM in 1977 and was adopted by the U.S. government but export was restricted due to security concerns, though free software is now widely available. NIST will not recertify DES and is accepting submissions for its AES replacement standard.
The document outlines the course map for a three day introduction to PKI technology course. Day one covers topics like cryptography fundamentals, symmetric and asymmetric encryption algorithms, digital signatures, and labs on encryption, signatures, and SSH. Day two covers PKI concepts like certificates, CRLs, CAs, and labs on S/MIME and SSL. Day three covers IPsec, case studies, and an open discussion. The objectives are to understand cryptographic concepts, PKI elements and applications, and why PKI enables e-commerce security.
The document discusses data encryption using the Data Encryption Standard (DES) and Triple DES (TDES) functionality in Spartan-II FPGAs. It describes how DES and TDES are commonly used encryption algorithms and how a FPGA-based solution from Xilinx and Xentec provides scalability, flexibility and performance for applications requiring data encryption. It also provides technical details on how the DES algorithm works using permutations, substitutions and XOR operations over multiple rounds to encrypt data blocks.
In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot. Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor.
Introduction to Public key Cryptosystems with block diagrams
Reference : Cryptography and Network Security Principles and Practice , Sixth Edition , William Stalling
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.
This document discusses the implementation of a hybrid cryptography algorithm combining DES and IDEA. It begins by providing background on encryption, key escrow schemes, and the need for stronger algorithms. It then separately describes DES and IDEA, including their structure, performance analysis, and types of cryptanalysis attacks they are susceptible to. The document proposes a new hybrid algorithm combining DES and IDEA to improve security and integrity.
Cryptographic Algorithms For Secure Data CommunicationCSCJournals
Personal privacy is of utmost importance in the global networked world. One of the best tools to help people safeguard their personal information is the use of cryptography. In this paper we present new cryptographic algorithms that employ the use of asymmetric keys. The proposed algorithms encipher message into nonlinear equations using public key and decipher by the intended party using private key. If a third party intercepted the message, it will be difficult to decipher it due to the multilevel ciphers of the proposed application.
This document summarizes a technical seminar on hybrid encryption technology. Hybrid encryption combines both symmetric and asymmetric encryption algorithms to provide increased security. The seminar overviewed hybrid encryption using DES and RSA, as well as RSA and Diffie-Hellman. It also discussed how hybrid encryption can be applied to electronic documents, such as with Adobe Acrobat, to encrypt a document symmetrically but the symmetric key asymmetrically for different recipients. The seminar concluded that hybrid encryption removes the key distribution problem and increases security over only using a single cryptographic algorithm.
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 provides an overview of cryptography from classical to modern times. It discusses the history and evolution of cryptographic techniques including substitution ciphers, transposition ciphers, codes, public key cryptography, digital signatures, and key distribution problems. The document also summarizes the four main topics that will be covered in the course: the history and foundations of modern cryptography, using cryptography in practice, the theory of cryptography including proofs and definitions, and a special topic in cryptography.
The document summarizes the Data Encryption Standard (DES) algorithm in three main steps:
1. It provides background on how DES was developed by the National Bureau of Standards in response to growing needs for data encryption. DES was adopted as a standard in 1977.
2. It explains the basic mechanics of how DES works, including that it operates on 64-bit blocks of plaintext using 56-bit keys, and generates subkeys through permutations and shifts of the main key.
3. It gives an example of encrypting a sample plaintext message in hexadecimal using DES, showing how the message is padded and divided into blocks for encryption.
Advanced Encryption Standard (AES) Implementaion using JavaSunil Kumar R
The document describes a project report on the implementation of the AES encryption algorithm. It was submitted by two students, Sunil Kumar R and Shreekant, in partial fulfillment of the requirements for a Bachelor of Engineering degree in computer science. The project was carried out under the guidance of three faculty members at R.V. College of Engineering in Bangalore. It includes a certificate signed by the faculty confirming the students' satisfactory completion of the project.
This document provides an overview of cryptography concepts including encryption, authentication, and Java cryptography. It discusses symmetric and asymmetric encryption algorithms, digital signatures, hashing, and key management. It also describes how cryptography is implemented in Java through the Java Cryptography Architecture (JCA) and Java Cryptography Extension (JCE).
This document describes a password-based encryption standard (PKCS #5) that defines two key derivation algorithms combining message digest algorithms (MD2 and MD5) with DES encryption. The standard defines processes for encrypting and decrypting messages using a password, salt value, and iteration count to derive the encryption key. The encryption process formats the message and padding into a block, derives the key from the password/salt/count, and encrypts the block with DES-CBC. The decryption process reverses these steps to recover the original message.
This document discusses key exchange protocols and the Dolev-Yao threat model. It summarizes various key exchange protocols, including their vulnerabilities to attacks by an attacker ("Malice"). It proposes improvements to the protocols, such as adding nonces or message authentication, to prevent attacks like replay or man-in-the-middle attacks. The document ultimately presents a public key authentication protocol that aims to prevent the attacks on previous protocols.
WP101 Fundamental Principles of Network SecuritySE_NAM_Training
This document provides an overview of fundamental principles of network security. It discusses how security incidents are rising each year as threats become more complex, requiring more robust security measures. The document covers security basics, basic network host security, securing access to devices and systems, secure access protocols, and best practices for network security. It emphasizes that securing modern networks demands an end-to-end approach with understanding of vulnerabilities and protective measures, and that vigilance is needed given increasing attacks.
This document provides an overview of CMPSCI 453, an introductory computer networking course. The course will be taught by Professor Jim Kurose and will cover networking principles and the Internet architecture using a top-down approach. Students will learn about topics like physical media, protocol layers, routing, and link-level protocols. The workload includes homework assignments, programming projects, lab assignments, and exams. All course materials will be available on the class website at gaia.cs.umass.edu/cs453.
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.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Bluetooth technology is an emerging wireless networking standard, which is based on chip that provides short-range wireless frequency hopping communication. Now, Bluetooth technology is mainly applied to the communication between mobile terminal devices, such as palm computers, mobile phones, laptops and so on. However, the phenomenon of data-leaking frequently arises in using the Bluetooth technology for data transfer. To enhance the security of data transmission in Bluetooth communication, a hybrid encryption algorithm based on DES and RSA is proposed. The currently used encryption algorithm employed by the Bluetooth to protect the confidentiality of data during transport between two or more devices is a 128-bit symmetric stream cipher called E0. The proposed hybrid encryption algorithm, instead of the E0 encryption, DES algorithm is used for data transmission because of its higher efficiency in block encryption, and RSA algorithm is used for the encryption of the key of the DES because of its management advantages in key cipher. Under the dual protection with the DES algorithm and the RSA algorithm, the data transmission in the Bluetooth system will be more secure. This project is extended with triple des in place of des to enhance more security.
DES is a widely-used method of data encryption that uses a private key chosen from 72 quadrillion possible keys to encrypt 64-bit blocks of data using 16 rounds of operations. While DES is considered strong encryption, some use triple DES for additional security. In 1997, a cooperative effort of 14,000 computers broke a DES encrypted message by trying 18 quadrillion keys out of the 72 quadrillion possibilities. DES originated at IBM in 1977 and was adopted by the U.S. government but export was restricted due to security concerns, though free software is now widely available. NIST will not recertify DES and is accepting submissions for its AES replacement standard.
The document outlines the course map for a three day introduction to PKI technology course. Day one covers topics like cryptography fundamentals, symmetric and asymmetric encryption algorithms, digital signatures, and labs on encryption, signatures, and SSH. Day two covers PKI concepts like certificates, CRLs, CAs, and labs on S/MIME and SSL. Day three covers IPsec, case studies, and an open discussion. The objectives are to understand cryptographic concepts, PKI elements and applications, and why PKI enables e-commerce security.
The document discusses data encryption using the Data Encryption Standard (DES) and Triple DES (TDES) functionality in Spartan-II FPGAs. It describes how DES and TDES are commonly used encryption algorithms and how a FPGA-based solution from Xilinx and Xentec provides scalability, flexibility and performance for applications requiring data encryption. It also provides technical details on how the DES algorithm works using permutations, substitutions and XOR operations over multiple rounds to encrypt data blocks.
In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot. Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor.
Introduction to Public key Cryptosystems with block diagrams
Reference : Cryptography and Network Security Principles and Practice , Sixth Edition , William Stalling
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.
This document discusses the implementation of a hybrid cryptography algorithm combining DES and IDEA. It begins by providing background on encryption, key escrow schemes, and the need for stronger algorithms. It then separately describes DES and IDEA, including their structure, performance analysis, and types of cryptanalysis attacks they are susceptible to. The document proposes a new hybrid algorithm combining DES and IDEA to improve security and integrity.
Cryptographic Algorithms For Secure Data CommunicationCSCJournals
Personal privacy is of utmost importance in the global networked world. One of the best tools to help people safeguard their personal information is the use of cryptography. In this paper we present new cryptographic algorithms that employ the use of asymmetric keys. The proposed algorithms encipher message into nonlinear equations using public key and decipher by the intended party using private key. If a third party intercepted the message, it will be difficult to decipher it due to the multilevel ciphers of the proposed application.
This document summarizes a technical seminar on hybrid encryption technology. Hybrid encryption combines both symmetric and asymmetric encryption algorithms to provide increased security. The seminar overviewed hybrid encryption using DES and RSA, as well as RSA and Diffie-Hellman. It also discussed how hybrid encryption can be applied to electronic documents, such as with Adobe Acrobat, to encrypt a document symmetrically but the symmetric key asymmetrically for different recipients. The seminar concluded that hybrid encryption removes the key distribution problem and increases security over only using a single cryptographic algorithm.
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 provides an overview of cryptography from classical to modern times. It discusses the history and evolution of cryptographic techniques including substitution ciphers, transposition ciphers, codes, public key cryptography, digital signatures, and key distribution problems. The document also summarizes the four main topics that will be covered in the course: the history and foundations of modern cryptography, using cryptography in practice, the theory of cryptography including proofs and definitions, and a special topic in cryptography.
The document summarizes the Data Encryption Standard (DES) algorithm in three main steps:
1. It provides background on how DES was developed by the National Bureau of Standards in response to growing needs for data encryption. DES was adopted as a standard in 1977.
2. It explains the basic mechanics of how DES works, including that it operates on 64-bit blocks of plaintext using 56-bit keys, and generates subkeys through permutations and shifts of the main key.
3. It gives an example of encrypting a sample plaintext message in hexadecimal using DES, showing how the message is padded and divided into blocks for encryption.
Advanced Encryption Standard (AES) Implementaion using JavaSunil Kumar R
The document describes a project report on the implementation of the AES encryption algorithm. It was submitted by two students, Sunil Kumar R and Shreekant, in partial fulfillment of the requirements for a Bachelor of Engineering degree in computer science. The project was carried out under the guidance of three faculty members at R.V. College of Engineering in Bangalore. It includes a certificate signed by the faculty confirming the students' satisfactory completion of the project.
This document provides an overview of cryptography concepts including encryption, authentication, and Java cryptography. It discusses symmetric and asymmetric encryption algorithms, digital signatures, hashing, and key management. It also describes how cryptography is implemented in Java through the Java Cryptography Architecture (JCA) and Java Cryptography Extension (JCE).
This document describes a password-based encryption standard (PKCS #5) that defines two key derivation algorithms combining message digest algorithms (MD2 and MD5) with DES encryption. The standard defines processes for encrypting and decrypting messages using a password, salt value, and iteration count to derive the encryption key. The encryption process formats the message and padding into a block, derives the key from the password/salt/count, and encrypts the block with DES-CBC. The decryption process reverses these steps to recover the original message.
This document discusses key exchange protocols and the Dolev-Yao threat model. It summarizes various key exchange protocols, including their vulnerabilities to attacks by an attacker ("Malice"). It proposes improvements to the protocols, such as adding nonces or message authentication, to prevent attacks like replay or man-in-the-middle attacks. The document ultimately presents a public key authentication protocol that aims to prevent the attacks on previous protocols.
WP101 Fundamental Principles of Network SecuritySE_NAM_Training
This document provides an overview of fundamental principles of network security. It discusses how security incidents are rising each year as threats become more complex, requiring more robust security measures. The document covers security basics, basic network host security, securing access to devices and systems, secure access protocols, and best practices for network security. It emphasizes that securing modern networks demands an end-to-end approach with understanding of vulnerabilities and protective measures, and that vigilance is needed given increasing attacks.
This document provides an overview of CMPSCI 453, an introductory computer networking course. The course will be taught by Professor Jim Kurose and will cover networking principles and the Internet architecture using a top-down approach. Students will learn about topics like physical media, protocol layers, routing, and link-level protocols. The workload includes homework assignments, programming projects, lab assignments, and exams. All course materials will be available on the class website at gaia.cs.umass.edu/cs453.
The document summarizes key concepts about the transport layer in computer networks. It discusses how the transport layer provides logical communication between application processes running on different hosts using protocols like TCP and UDP. TCP provides reliable, in-order delivery using congestion control and flow control, while UDP provides unreliable delivery without these features. The outline and chapters cover transport layer services, multiplexing/demultiplexing, connection-oriented transport with TCP, and congestion control principles.
This document provides an overview and introduction to the key concepts of computer networks and the Internet. It discusses what the Internet is, including its nuts and bolts view consisting of interconnected hosts, communication links, and routers. It also covers the network edge consisting of end systems and various access networks, the network core consisting of interconnected routers, and different types of physical media used for communication links. Key concepts explained include circuit switching versus packet switching, protocols, and the layered architecture of the Internet.
This document provides a summary of policies for information security at RLK Products. It outlines the job description and qualifications for an Information Assurance/Security Officer who will be responsible for developing and implementing a comprehensive security program. The policies describe requirements for privacy, acceptable use, staff responsibilities, and compliance with regulations. Incident response procedures, risk assessments, training, and an emergency plan are part of maintaining security.
The document summarizes key topics in network application layer protocols. It discusses principles of network applications and popular protocols like HTTP, FTP, SMTP, and DNS. It covers client-server and peer-to-peer architectures, socket programming, and how processes are addressed. The document also examines common network applications and the transport service requirements around data loss, bandwidth needs, and time sensitivity.
This chapter discusses the network layer, including:
1) The key functions of the network layer including forwarding, routing, and connection setup.
2) Network layer service models such as best effort, connection-oriented, and guaranteed services.
3) The differences between virtual circuit and datagram networks, and how routers implement virtual circuits using forwarding tables and connection state information.
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.
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.
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.
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.
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
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.
Cryptography techniques allow for message confidentiality, authentication, and integrity. Symmetric key cryptography uses a shared secret key where the sender and receiver both know the key. Public key cryptography uses key pairs where one key is public and one is private. RSA is an example of an asymmetric encryption algorithm that uses a public/private key pair based on the difficulty of factoring large numbers. Message integrity is ensured through techniques like digital signatures that authenticate the source and content of messages.
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.
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.
Chapter 8SecurityComputer Networking A Top Down Approach .docxrusselldayna
Chapter 8
Security
Computer Networking: A Top Down Approach
6th edition
Jim Kurose, Keith Ross
Addison-Wesley
March 2012
A note on the use of these ppt slides:
We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following:
If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!)
If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material.
Thanks and enjoy! JFK/KWR
All material copyright 1996-2012
J.F Kurose and K.W. Ross, All Rights Reserved
Network Security
Chapter 8: Network Security
Chapter goals:
understand principles of network security:
cryptography and its many uses beyond “confidentiality”
authentication
message integrity
security in practice:
firewalls and intrusion detection systems
security in application, transport, network, link layers
2
Network Security
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity, authentication
8.4 Securing e-mail
8.5 Securing TCP connections: SSL
8.6 Network layer security: IPsec
8.7 Securing wireless LANs
8.8 Operational security: firewalls and IDS
3
Network Security
What is network security?
confidentiality: only sender, intended receiver should “understand” message contents
sender encrypts message
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
4
Network Security
Friends and enemies: Alice, Bob, Trudy
well-known in network security world
Bob, Alice (lovers!) want to communicate “securely”
Trudy (intruder) may intercept, delete, add messages
5
Network Security
Who might Bob, Alice be?
… well, real-life Bobs and Alices!
Web browser/server for electronic transactions (e.g., on-line purchases)
on-line banking client/server
DNS servers
routers exchanging routing table updates
other examples?
6
Network Security
There are bad guys (and girls) out there!
Q: What can a “bad guy” do?
A: A lot! See section 1.6
eavesdrop: intercept messages
actively insert messages into connection
impersonation: can fake (spoof) source address in packet (or any field in packet)
hijacking: “take over” ongoing connection by removing sender or receiver, inserting himself in place
denial of service: prevent service from being used by others (e.g., by overloading resources)
7
Network Security
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptograph ...
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.
1. Chapter 8: Network Security
Chapter goals:
understand principles of network security:
cryptography and its many uses beyond
“confidentiality”
authentication
message integrity
key distribution
security in practice:
firewalls
security in application, transport, network, link
layers
8: Network Security 8-1
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-2
1
2. What is network security?
Confidentiality: only sender, intended receiver
should “understand” message contents
sender encrypts message
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
8: Network Security 8-3
Friends and enemies: Alice, Bob, Trudy
well-known in network security world
Bob, Alice (lovers!) want to communicate “securely”
Trudy (intruder) may intercept, delete, add messages
Alice Bob
data, control
channel
messages
data secure secure data
sender receiver
Trudy
8: Network Security 8-4
2
3. Who might Bob, Alice be?
… well, real-life Bobs and Alices!
Web browser/server for electronic
transactions (e.g., on-line purchases)
on-line banking client/server
DNS servers
routers exchanging routing table updates
other examples?
8: Network Security 8-5
There are bad guys (and girls) out there!
Q: What can a “bad guy” do?
A: a lot!
eavesdrop: intercept messages
actively insert messages into connection
impersonation: can fake (spoof) source address
in packet (or any field in packet)
hijacking: “take over” ongoing connection by
removing sender or receiver, inserting himself
in place
denial of service: prevent service from being
used by others (e.g., by overloading resources)
more on this later ……
8: Network Security 8-6
3
4. Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-7
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)
8: Network Security 8-8
4
5. Symmetric key cryptography
substitution cipher: substituting one thing for another
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?
8: Network Security 8-9
Symmetric key cryptography
KA-B KA-B
plaintext encryption ciphertext decryption plaintext
message, m algorithm algorithm
K (m) m = K ( KA-B(m) )
A-B A-B
symmetric key crypto: Bob and Alice share know same
(symmetric) key: K
A-B
e.g., key is knowing substitution pattern in mono
alphabetic substitution cipher
Q: how do Bob and Alice agree on key value?
8: Network Security 8-10
5
6. Symmetric key crypto: DES
DES: Data Encryption Standard
US encryption standard [NIST 1993]
56-bit symmetric key, 64-bit plaintext input
How secure is DES?
DES Challenge: 56-bit-key-encrypted phrase
(“Strong cryptography makes the world a safer
place”) decrypted (brute force) in 4 months
no known “backdoor” decryption approach
making DES more secure:
use three keys sequentially (3-DES) on each datum
use cipher-block chaining
8: Network Security 8-11
Symmetric key
crypto: DES
DES operation
initial permutation
16 identical “rounds” of
function application,
each using different
48 bits of key
final permutation
8: Network Security 8-12
6
7. AES: Advanced Encryption Standard
new (Nov. 2001) symmetric-key NIST
standard, replacing DES
processes data in 128 bit blocks
128, 192, or 256 bit keys
brute force decryption (try each key)
taking 1 sec on DES, takes 149 trillion
years for AES
8: Network Security 8-13
Public Key Cryptography
symmetric key crypto public key cryptography
requires sender, radically different
receiver know shared approach [Diffie-
secret key Hellman76, RSA78]
Q: how to agree on key sender, receiver do
in first place not share secret key
(particularly if never public encryption key
“met”)? known to all
private decryption
key known only to
receiver
8: Network Security 8-14
7
8. 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
8: Network Security 8-15
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 KB
RSA: Rivest, Shamir, Adelson algorithm
8: Network Security 8-16
8
9. 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
8: Network Security 8-17
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)
m = (m e mod n) d mod n
Magic
happens!
c
8: Network Security 8-18
9
10. 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
8: Network Security 8-19
RSA: Why is that m = (m e mod n) d 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
8: Network Security 8-20
10
11. 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!
8: Network Security 8-21
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-22
11
12. Authentication
Goal: Bob wants Alice to “prove” her identity
to him
Protocol ap1.0: Alice says “I am Alice”
“I am Alice”
Failure scenario??
8: Network Security 8-23
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
8: Network Security 8-24
12
13. 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??
8: Network Security 8-25
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
“spoofing”
Alice’s
IP address
“I am Alice” Alice’s address
8: Network Security 8-26
13
14. 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
8: Network Security 8-27
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
8: Network Security 8-28
14
15. 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
8: Network Security 8-29
Authentication: another try
Protocol ap3.1: Alice says “I am Alice” and sends her
encrypted secret password to “prove” it.
Alice’s encrypted
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
8: Network Security 8-30
15
16. 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!
8: Network Security 8-31
Authentication: ap5.0
ap4.0 requires shared symmetric key
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
8: Network Security 8-32
16
17. 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) T to Alice
sends m T
A
- + encrypted with
m = K (K (m))
A A Alice’s public key
8: Network Security 8-33
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!
8: Network Security 8-34
17
18. Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Message integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-35
Digital Signatures
Cryptographic technique analogous to hand-
written signatures.
sender (Bob) digitally signs document,
establishing he is document owner/creator.
verifiable, nonforgeable: recipient (Alice) can
prove to someone that Bob, and no one else
(including Alice), must have signed document
8: Network Security 8-36
18
19. Digital Signatures
Simple digital signature for message m:
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
8: Network Security 8-37
Digital Signatures (more)
-
Suppose Alice receives msg m, digital signature KB(m)
Alice verifies m signed by Bob by applying Bob’s
+ - + -
public key KB to KB(m) then checks KB(KB(m) ) = m.
+ -
If KB(KB(m) ) = m, whoever signed m must have used
Bob’s private key.
Alice thus verifies that:
Bob signed m.
No one else signed m.
Bob signed m and not m’.
Non-repudiation:
-
Alice can take m, and signature KB(m) to
court and prove that Bob signed m.
8: Network Security 8-38
19
20. 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 many-to-1
“fingerprint”
produces fixed-size msg
apply hash function H digest (fingerprint)
to m, get fixed size
given message digest x,
message digest, H(m).
computationally
infeasible to find m such
that x = H(m)
8: Network Security 8-39
Internet checksum: poor crypto hash
function
Internet checksum has some properties of hash function:
produces fixed length digest (16-bit sum) of message
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
IO U 1 49 4F 55 31 IO U 9 49 4F 55 39
0 0.9 30 30 2E 39 0 0.1 30 30 2E 31
9B O B 39 42 D2 42 9B O B 39 42 D2 42
B2 C1 D2 AC different messages B2 C1 D2 AC
but identical checksums!
8: Network Security 8-40
20
21. 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
?
8: Network Security 8-41
Hash Function Algorithms
MD5 hash function widely used (RFC 1321)
computes 128-bit message digest in 4-step
process.
arbitrary 128-bit string x, appears difficult to
construct msg m whose MD5 hash is equal to x.
SHA-1 is also used.
US standard [NIST, FIPS PUB 180-1]
160-bit message digest
8: Network Security 8-42
21
22. Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-43
Trusted Intermediaries
Symmetric key problem: Public key problem:
How do two entities 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
trusted key distribution key, not Trudy’s?
center (KDC) acting as
intermediary between Solution:
entities trusted certification
authority (CA)
8: Network Security 8-44
22
23. Key Distribution Center (KDC)
Alice, Bob need shared symmetric key.
KDC: server shares different secret key with each
registered user (many users)
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
8: Network Security 8-45
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
8: Network Security 8-46
23
24. Certification Authorities
Certification authority (CA): binds public key to
particular entity, E.
E (person, router) registers its public key with CA.
E provides “proof of identity” to CA.
CA creates certificate binding E to its public key.
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
Bob’s private -
K CA
identifying key Bob’s public key,
information signed by CA
8: Network Security 8-47
Certification Authorities
When Alice wants Bob’s public key:
gets Bob’s certificate (Bob or elsewhere).
apply CA’s public key to Bob’s certificate, get
Bob’s public key
+ digital Bob’s
KB signature public
+
(decrypt) KB key
CA
public +
K CA
key
8: Network Security 8-48
24
25. A certificate contains:
Serial number (unique to issuer)
info about certificate owner, including algorithm
and key value itself (not shown)
info about
certificate
issuer
valid dates
digital
signature by
issuer
8: Network Security 8-49
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-50
25
26. Firewalls
firewall
isolates organization’s internal net from larger
Internet, allowing some packets to pass,
blocking others.
administered public
network Internet
firewall
8: Network Security 8-51
Firewalls: Why
prevent denial of service attacks:
SYN flooding: attacker establishes many bogus
TCP connections, no resources left for “real”
connections.
prevent illegal modification/access of internal data.
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:
application-level
packet-filtering
8: Network Security 8-52
26
27. Should arriving
Packet Filtering packet be allowed
in? Departing packet
let out?
internal network connected to Internet via
router firewall
router filters packet-by-packet, decision to
forward/drop packet based on:
source IP address, destination IP address
TCP/UDP source and destination port numbers
ICMP message type
TCP SYN and ACK bits
8: Network Security 8-53
Packet Filtering
Example 1: block incoming and outgoing
datagrams with IP protocol field = 17 and with
either source or dest port = 23.
All incoming and outgoing UDP flows and telnet
connections are blocked.
Example 2: Block inbound TCP segments with
ACK=0.
Prevents external clients from making TCP
connections with internal clients, but allows
internal clients to connect to outside.
8: Network Security 8-54
27
28. Application gateways gateway-to-remote
host telnet session
host-to-gateway
telnet session
Filters packets on
application data as well application
gateway
router and filter
as on IP/TCP/UDP fields.
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.
8: Network Security 8-55
Limitations of firewalls and gateways
IP spoofing: router filters often use all or
can’t know if data nothing policy for UDP.
“really” comes from tradeoff: degree of
claimed source communication with
if multiple app’s. need outside world, level of
special treatment, each security
has own app. gateway. many highly protected
client software must sites still suffer from
know how to contact attacks.
gateway.
e.g., must set IP address
of proxy in Web
browser
8: Network Security 8-56
28
29. Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8: Network Security 8-57
Internet security threats
Mapping:
before attacking: “case the joint” – find out
what services are implemented on network
Use ping to determine what hosts have
addresses on network
Port-scanning: try to establish TCP connection
to each port in sequence (see what happens)
nmap (http://www.insecure.org/nmap/) mapper:
“network exploration and security auditing”
Countermeasures?
8: Network Security 8-58
29
30. Internet security threats
Mapping: countermeasures
record traffic entering network
look for suspicious activity (IP addresses, ports
being scanned sequentially)
8: Network Security 8-59
Internet security threats
Packet sniffing:
broadcast media
promiscuous NIC reads all packets passing by
can read all unencrypted data (e.g. passwords)
e.g.: C sniffs B’s packets
A C
src:B dest:A payload
B
Countermeasures?
8: Network Security 8-60
30
31. Internet security threats
Packet sniffing: countermeasures
all hosts in organization run software that
checks periodically if host interface in
promiscuous mode.
one host per segment of broadcast media
(switched Ethernet at hub)
A C
src:B dest:A payload
B
8: Network Security 8-61
Internet security threats
IP Spoofing:
can generate “raw” IP packets directly from
application, putting any value into IP source
address field
receiver can’t tell if source is spoofed
e.g.: C pretends to be B
A C
src:B dest:A payload
B
Countermeasures?
8: Network Security 8-62
31
32. Internet security threats
IP Spoofing: ingress filtering
routers should not forward outgoing packets
with invalid source addresses (e.g., datagram
source address not in router’s network)
great, but ingress filtering can not be mandated
for all networks
A C
src:B dest:A payload
B
8: Network Security 8-63
Internet security threats
Denial of service (DOS):
flood of maliciously generated packets “swamp”
receiver
Distributed DOS (DDOS): multiple coordinated
sources swamp receiver
e.g., C and remote host SYN-attack A
A C
SYN
SYN
SYN SYN SYN
B
Countermeasures?
SYN
SYN
8: Network Security 8-64
32
33. Internet security threats
Denial of service (DOS): countermeasures
filter out flooded packets (e.g., SYN) before
reaching host: throw out good with bad
traceback to source of floods (most likely an
innocent, compromised machine)
A C
SYN
SYN
SYN SYN SYN
B
SYN
SYN
8: Network Security 8-65
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Authentication
8.4 Integrity
8.5 Key Distribution and certification
8.6 Access control: firewalls
8.7 Attacks and counter measures
8.8 Security in many layers
8.8.1. Secure email
8.8.2. Secure sockets
8.8.3. IPsec
8.8.4. Security in 802.11
8: Network Security 8-66
33
34. Secure e-mail
Alice wants to send confidential e-mail, m, to Bob.
KS
KS(m ) KS(m )
m KS( ). KS( ) . m
+ Internet
- KS
KS
+ .
K B( ) + +
-
K B( ) .
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.
8: Network Security 8-67
Secure e-mail
Alice wants to send confidential e-mail, m, to Bob.
KS
KS(m ) KS(m )
m KS( ). KS( ) . m
+ Internet
- KS
KS
+ .
K B( ) + +
-
K B( ) .
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
8: Network Security 8-68
34
35. Secure e-mail (continued)
• Alice wants to provide sender authentication
message integrity.
- KA
+
KA
- -
KA(H(m)) KA(H(m)) + .
m .
H( )
-
KA( ) . KA( ) H(m )
+ Internet
- compare
m H( ). H(m )
m
• Alice digitally signs message.
• sends both message (in the clear) and digital signature.
8: Network Security 8-69
Secure e-mail (continued)
• Alice wants to provide secrecy, sender authentication,
message integrity.
-
KA
-
- . KA(H(m))
m .
H( ) KA( ) KS
+ KS( ).
m + Internet
KS
+ .
K B( ) +
KB(KS )
K
+
B
Alice uses three keys: her private key, Bob’s public
key, newly created symmetric key
8: Network Security 8-70
35
36. Pretty good privacy (PGP)
Internet e-mail encryption A PGP signed message:
scheme, de-facto standard.
---BEGIN PGP SIGNED MESSAGE---
uses symmetric key Hash: SHA1
cryptography, public key
cryptography, hash Bob:My husband is out of town
function, and digital
tonight.Passionately yours,
Alice
signature as described.
provides secrecy, sender ---BEGIN PGP SIGNATURE---
authentication, integrity. Version: PGP 5.0
Charset: noconv
inventor, Phil Zimmerman, yhHJRHhGJGhgg/12EpJ+lo8gE4vB3mqJ
was target of 3-year hFEvZP9t6n7G6m5Gw2
federal investigation. ---END PGP SIGNATURE---
8: Network Security 8-71
Secure sockets layer (SSL)
transport layer server authentication:
security to any TCP- SSL-enabled browser
includes public keys for
based app using SSL trusted CAs.
services. Browser requests
server certificate,
used between Web issued by trusted CA.
browsers, servers for Browser uses CA’s
e-commerce (shttp). public key to extract
server’s public key from
security services: certificate.
server authentication
check your browser’s
data encryption security menu to see
client authentication its trusted CAs.
(optional)
8: Network Security 8-72
36
37. SSL (continued)
Encrypted SSL session: SSL: basis of IETF
Browser generates Transport Layer
symmetric session key, Security (TLS).
encrypts it with server’s SSL can be used for
public key, sends non-Web applications,
encrypted key to server. e.g., IMAP.
Using private key, server Client authentication
decrypts session key. can be done with client
Browser, server know certificates.
session key
All data sent into TCP
socket (by client or server)
encrypted with session key.
8: Network Security 8-73
IPsec: Network Layer Security
Network-layer secrecy:
For both AH and ESP, source,
sending host encrypts the
destination handshake:
data in IP datagram
create network-layer
TCP and UDP segments;
logical channel called a
ICMP and SNMP
security association (SA)
messages.
Each SA unidirectional.
Network-layer authentication
Uniquely determined by:
destination host can
authenticate source IP security protocol (AH or
address ESP)
Two principle protocols: source IP address
authentication header 32-bit connection ID
(AH) protocol
encapsulation security
payload (ESP) protocol
8: Network Security 8-74
37
38. Authentication Header (AH) Protocol
provides source AH header includes:
authentication, data connection identifier
integrity, no authentication data:
confidentiality source- signed message
AH header inserted digest calculated over
between IP header, original IP datagram.
data field. next header field:
protocol field: 51 specifies type of data
intermediate routers (e.g., TCP, UDP, ICMP)
process datagrams as
usual
IP header AH header data (e.g., TCP, UDP segment)
8: Network Security 8-75
ESP Protocol
provides secrecy, host ESP authentication
authentication, data field is similar to AH
integrity. authentication field.
data, ESP trailer Protocol = 50.
encrypted.
next header field is in ESP
trailer.
authenticated
encrypted
ESP ESP ESP
IP header TCP/UDP segment
header trailer authent.
8: Network Security 8-76
38
39. IEEE 802.11 security
War-driving: drive around Bay area, see what 802.11
networks available?
More than 9000 accessible from public roadways
85% use no encryption/authentication
packet-sniffing and various attacks easy!
Securing 802.11
encryption, authentication
first attempt at 802.11 security: Wired Equivalent
Privacy (WEP): a failure
current attempt: 802.11i
8: Network Security 8-77
Wired Equivalent Privacy (WEP):
authentication as in protocol ap4.0
host requests authentication from access point
access point sends 128 bit nonce
host encrypts nonce using shared symmetric key
access point decrypts nonce, authenticates host
no key distribution mechanism
authentication: knowing the shared key is enough
8: Network Security 8-78
39
40. WEP data encryption
Host/AP share 40 bit symmetric key (semi-
permanent)
Host appends 24-bit initialization vector (IV) to
create 64-bit key
64 bit key used to generate stream of keys, kiIV
kiIV used to encrypt ith byte, di, in frame:
ci = di XOR kiIV
IV and encrypted bytes, ci sent in frame
8: Network Security 8-79
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
IV plus CRC
plaintext header
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
8: Network Security 8-80
40
41. Breaking 802.11 WEP encryption
Security hole:
24-bit IV, one IV per frame, -> IV’s eventually reused
IV transmitted in plaintext -> IV reuse detected
Attack:
Trudy causes Alice to encrypt known plaintext d1 d2
d3 d4 …
Trudy sees: ci = di XOR kiIV
Trudy knows ci di, so can compute kiIV
Trudy knows encrypting key sequence k1IV k2IV k3IV …
Next time IV is used, Trudy can decrypt!
8: Network Security 8-81
802.11i: improved security
numerous (stronger) forms of encryption
possible
provides key distribution
uses authentication server separate from
access point
8: Network Security 8-82
41
42. 802.11i: four phases of operation
STA: AP: access point AS:
client station wired Authentication
network server
1 Discovery of
security capabilities
2 STA and AS mutually authenticate, together
generate Master Key (MK). AP servers as “pass through”
3 STA derives 3 AS derives
Pairwise Master
same PMK,
Key (PMK)
sends to AP
4 STA, AP use PMK to derive
Temporal Key (TK) used for message
encryption, integrity 8: Network Security 8-83
EAP: extensible authentication protocol
EAP: end-end client (mobile) to authentication
server protocol
EAP sent over separate “links”
mobile-to-AP (EAP over LAN)
AP to authentication server (RADIUS over UDP)
wired
network
EAP TLS
EAP
EAP over LAN (EAPoL) RADIUS
IEEE 802.11 UDP/IP
8: Network Security 8-84
42
43. Network Security (summary)
Basic techniques…...
cryptography (symmetric and public)
authentication
message integrity
key distribution
…. used in many different security scenarios
secure email
secure transport (SSL)
IP sec
802.11
8: Network Security 8-85
43