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 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.
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 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
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 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.
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 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
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.
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 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 discusses cryptography and how it can be used to secure communication. It covers symmetric and public key encryption, digital signatures, hashes, and authentication. Symmetric encryption uses a shared secret key for both encryption and decryption, while public key encryption uses different keys for encryption and decryption. Cryptographic hashes provide integrity for messages, and message authentication codes (MACs) also provide integrity and authentication. Digital signatures provide authentication and integrity using public key cryptography. The document discusses encryption modes like CBC and stream ciphers like RC4. It also covers key distribution challenges and how certificate authorities can help authenticate servers.
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.
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.
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 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 Security Problem
Program Threats
System and Network Threats
Cryptography as a Security Tool
User Authentication
Implementing Security Defenses
Firewalling to Protect Systems and Networks
Computer-Security Classifications
An Example: Windows XP
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 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.
This document provides an overview of cryptography including:
1. Cryptography is the process of encoding messages to protect information and ensure confidentiality, integrity, authentication and other security goals.
2. There are symmetric and asymmetric encryption algorithms that use the same or different keys for encryption and decryption. Examples include AES, RSA, and DES.
3. Other techniques discussed include digital signatures, visual cryptography, and ways to implement cryptography like error diffusion and halftone visual cryptography.
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 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.
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
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.
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 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 discusses cryptography and how it can be used to secure communication. It covers symmetric and public key encryption, digital signatures, hashes, and authentication. Symmetric encryption uses a shared secret key for both encryption and decryption, while public key encryption uses different keys for encryption and decryption. Cryptographic hashes provide integrity for messages, and message authentication codes (MACs) also provide integrity and authentication. Digital signatures provide authentication and integrity using public key cryptography. The document discusses encryption modes like CBC and stream ciphers like RC4. It also covers key distribution challenges and how certificate authorities can help authenticate servers.
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.
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.
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 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 Security Problem
Program Threats
System and Network Threats
Cryptography as a Security Tool
User Authentication
Implementing Security Defenses
Firewalling to Protect Systems and Networks
Computer-Security Classifications
An Example: Windows XP
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 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.
This document provides an overview of cryptography including:
1. Cryptography is the process of encoding messages to protect information and ensure confidentiality, integrity, authentication and other security goals.
2. There are symmetric and asymmetric encryption algorithms that use the same or different keys for encryption and decryption. Examples include AES, RSA, and DES.
3. Other techniques discussed include digital signatures, visual cryptography, and ways to implement cryptography like error diffusion and halftone visual cryptography.
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 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.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
Software Engineering and Project Management - Introduction, Modeling Concepts...Prakhyath Rai
Introduction, Modeling Concepts and Class Modeling: What is Object orientation? What is OO development? OO Themes; Evidence for usefulness of OO development; OO modeling history. Modeling
as Design technique: Modeling, abstraction, The Three models. Class Modeling: Object and Class Concept, Link and associations concepts, Generalization and Inheritance, A sample class model, Navigation of class models, and UML diagrams
Building the Analysis Models: Requirement Analysis, Analysis Model Approaches, Data modeling Concepts, Object Oriented Analysis, Scenario-Based Modeling, Flow-Oriented Modeling, class Based Modeling, Creating a Behavioral Model.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
cnn.pptx Convolutional neural network used for image classication
Hardware Network Trojans for neural Networks
1. 8: Network Security 8-1
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. 8: Network Security 8-2
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
3. 8: Network Security 8-3
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. 8: Network Security 8-4
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
secure
sender
secure
receiver
channel data, control
messages
data data
Alice Bob
Trudy
5. 8: Network Security 8-5
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. 8: Network Security 8-6
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 ……
7. 8: Network Security 8-7
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
8. 8: Network Security 8-8
The language of cryptography
symmetric key crypto: sender, receiver keys identical
public-key crypto: encryption key public, decryption key
secret (private)
plaintext plaintext
ciphertext
K
A
encryption
algorithm
decryption
algorithm
Alice’s
encryption
key
Bob’s
decryption
key
K
B
9. 8: Network Security 8-9
Symmetric key cryptography
substitution cipher: substituting one thing for another
monoalphabetic cipher: substitute one letter for another
plaintext: abcdefghijklmnopqrstuvwxyz
ciphertext: mnbvcxzasdfghjklpoiuytrewq
Plaintext: bob. i love you. alice
ciphertext: nkn. s gktc wky. mgsbc
E.g.:
Q: How hard to break this simple cipher?:
brute force (how hard?)
other?
10. 8: Network Security 8-10
Symmetric key cryptography
symmetric key crypto: Bob and Alice share know same
(symmetric) key: K
e.g., key is knowing substitution pattern in mono
alphabetic substitution cipher
Q: how do Bob and Alice agree on key value?
plaintext
ciphertext
KA-B
encryption
algorithm
decryption
algorithm
A-B
KA-B
plaintext
message, m
K (m)
A-B
K (m)
A-B
m = K ( )
A-B
11. 8: Network Security 8-11
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
12. 8: Network Security 8-12
Symmetric key
crypto: DES
initial permutation
16 identical “rounds” of
function application,
each using different
48 bits of key
final permutation
DES operation
13. 8: Network Security 8-13
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
14. 8: Network Security 8-14
Block Cipher
one pass
through: one
input bit
affects eight
output bits
64-bit input
T1
8bits
8 bits
8bits
8 bits
8bits
8 bits
8bits
8 bits
8bits
8 bits
8bits
8 bits
8bits
8 bits
8bits
8 bits
64-bit scrambler
64-bit output
loop for
n rounds
T
2
T
3
T
4
T
6
T
5
T
7
T
8
multiple passes: each input bit afects all output bits
block ciphers: DES, 3DES, AES
15. 8: Network Security 8-15
Cipher Block Chaining
cipher block: if input
block repeated, will
produce same cipher
text:
t=1
m(1) = “HTTP/1.1”
block
cipher
c(1) = “k329aM02”
…
cipher block chaining:
XOR ith input block,
m(i), with previous
block of cipher text,
c(i-1)
c(0) transmitted to
receiver in clear
what happens in
“HTTP/1.1” scenario
from above?
+
m(i)
c(i)
t=17
m(17) = “HTTP/1.1”
block
cipher
c(17) = “k329aM02”
block
cipher
c(i-1)
16. 8: Network Security 8-16
Public key cryptography
symmetric key crypto
requires sender,
receiver know shared
secret key
Q: how to agree on key
in first place
(particularly if never
“met”)?
public key cryptography
radically different
approach [Diffie-
Hellman76, RSA78]
sender, receiver do
not share secret key
public encryption key
known to all
private decryption
key known only to
receiver
17. 8: Network Security 8-17
Public key cryptography
plaintext
message, m
ciphertext
encryption
algorithm
decryption
algorithm
Bob’s public
key
plaintext
message
K (m)
B
+
K
B
+
Bob’s private
key
K
B
-
m = K (K (m))
B
+
B
-
18. 8: Network Security 8-18
Public key encryption algorithms
need K ( ) and K ( ) such that
B B
. .
given public key K , it should be
impossible to compute
private key KB
B
Requirements:
1
2
RSA: Rivest, Shamir, Adleman algorithm
+ -
K (K (m)) = m
B
B
- +
+
-
19. 8: Network Security 8-19
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
-
20. 8: Network Security 8-20
RSA: Encryption, decryption
0. Given (n,e) and (n,d) as computed above
1. To encrypt bit pattern, m, compute
c = m mod n
e (i.e., remainder when m is divided by n)
e
2. To decrypt received bit pattern, c, compute
m = c mod n
d (i.e., remainder when c is divided by n)
d
m = (m mod n)
e mod n
d
Magic
happens!
c
21. 8: Network Security 8-21
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 = m mod n
e
l 12 1524832 17
c m = c mod n
d
17 481968572106750915091411825223071697 12
c
d
letter
l
encrypt:
decrypt:
22. 8: Network Security 8-22
RSA: Why is that m = (m mod n)
e mod n
d
(m mod n)
e
mod n = m mod n
d ed
Useful number theory result: If p,q prime and
n = pq, then:
x mod n = x mod n
y y mod (p-1)(q-1)
= m mod n
ed mod (p-1)(q-1)
= m mod n
1
= m
(using number theory result above)
(since we chose ed to be divisible by
(p-1)(q-1) with remainder 1 )
23. 8: Network Security 8-23
RSA: another important property
The following property will be very useful later:
K (K (m)) = m
B
B
- +
K (K (m))
B
B
+ -
=
use public key
first, followed
by private key
use private key
first, followed
by public key
Result is the same!
24. 8: Network Security 8-24
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
25. 8: Network Security 8-25
Message Integrity
Bob receives msg from Alice, wants to ensure:
message originally came from Alice
message not changed since sent by Alice
Cryptographic Hash:
takes input m, produces fixed length value, H(m)
e.g., as in Internet checksum
computationally infeasible to find two different
messages, x, y such that H(x) = H(y)
equivalently: given m = H(x), (x unknown), can not determine
x.
note: Internet checksum fails this requirement!
26. 8: Network Security 8-26
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:
I O U 1
0 0 . 9
9 B O B
49 4F 55 31
30 30 2E 39
39 42 4F 42
message ASCII format
B2 C1 D2 AC
I O U 9
0 0 . 1
9 B O B
49 4F 55 39
30 30 2E 31
39 42 4F 42
message ASCII format
B2 C1 D2 AC
different messages
but identical checksums!
27. 8: Network Security 8-27
Message Authentication Code
m
s
(shared secret)
(message)
H(.) H(m+s)
public
Internet
append
m H(m+s)
s
compare
m
H(m+s)
H(.)
H(m+s)
(shared secret)
28. 8: Network Security 8-28
MACs in practice
MD5 hash function widely used (RFC 1321)
computes 128-bit MAC in 4-step process.
arbitrary 128-bit string x, appears difficult to
construct msg m whose MD5 hash is equal to x
• recent (2005) attacks on MD5
SHA-1 is also used
US standard [NIST, FIPS PUB 180-1]
160-bit MAC
29. 8: Network Security 8-29
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
30. 8: Network Security 8-30
Digital Signatures
simple digital signature for message m:
Bob “signs” m by encrypting with his private key
KB, creating “signed” message, KB(m)
-
-
Dear Alice
Oh, how I have missed
you. I think of you all the
time! …(blah blah blah)
Bob
Bob’s message, m
public key
encryption
algorithm
Bob’s private
key
KB
-
Bob’s message, m,
signed (encrypted)
with his private key
KB
-
(m)
31. 8: Network Security 8-31
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.
-
32. 8: Network Security 8-32
large
message
m
H: hash
function H(m)
digital
signature
(encrypt)
Bob’s
private
key KB
-
+
Bob sends digitally signed
message:
Alice verifies signature and
integrity of digitally signed
message:
KB(H(m))
-
encrypted
msg digest
KB(H(m))
-
encrypted
msg digest
large
message
m
H: hash
function
H(m)
digital
signature
(decrypt)
H(m)
Bob’s
public
key KB
+
equal
?
Digital signature = signed MAC
33. 8: Network Security 8-33
Public Key Certification
public key problem:
When Alice obtains Bob’s public key (from web site,
e-mail, diskette), how does she know it is Bob’s
public key, not Trudy’s?
solution:
trusted certification authority (CA)
34. 8: Network Security 8-34
Certification Authorities
Certification Authority (CA): binds public key to
particular entity, E.
E 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
public
key KB
+
Bob’s
identifying
information
digital
signature
(encrypt)
CA
private
key
KCA
-
KB
+
certificate for
Bob’s public key,
signed by CA
-
KCA(K )
B
+
35. 8: Network Security 8-35
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
Bob’s
public
key
KB
+
digital
signature
(decrypt)
CA
public
key
KCA
+
KB
+
-
KCA(K )
B
+
36. 8: Network Security 8-36
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
37. 8: Network Security 8-37
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
38. 8: Network Security 8-38
Authentication
Goal: Bob wants Alice to “prove” her identity
to him
Protocol ap1.0: Alice says “I am Alice”
Failure scenario??
“I am Alice”
39. 8: Network Security 8-39
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
declares
herself to be Alice
“I am Alice”
40. 8: Network Security 8-40
Authentication: another try
Protocol ap2.0: Alice says “I am Alice” in an IP packet
containing her source IP address
Failure scenario??
“I am Alice”
Alice’s
IP address
41. 8: Network Security 8-41
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 address
“I am Alice”
Alice’s
IP address
42. 8: Network Security 8-42
Authentication: another try
Protocol ap3.0: Alice says “I am Alice” and sends her
secret password to “prove” it.
Failure scenario??
“I’m Alice”
Alice’s
IP addr
Alice’s
password
OK
Alice’s
IP addr
43. 8: Network Security 8-43
Authentication: another try
Protocol ap3.0: Alice says “I am Alice” and sends her
secret password to “prove” it.
playback attack: Trudy
records Alice’s packet
and later
plays it back to Bob
“I’m Alice”
Alice’s
IP addr
Alice’s
password
OK
Alice’s
IP addr
“I’m Alice”
Alice’s
IP addr
Alice’s
password
44. 8: Network Security 8-44
Authentication: yet another try
Protocol ap3.1: Alice says “I am Alice” and sends her
encrypted secret password to “prove” it.
Failure scenario??
“I’m Alice”
Alice’s
IP addr
encrypted
password
OK
Alice’s
IP addr
45. 8: Network Security 8-45
Authentication: another try
Protocol ap3.1: Alice says “I am Alice” and sends her
encrypted secret password to “prove” it.
record
and
playback
still works!
“I’m Alice”
Alice’s
IP addr
encrypted
password
OK
Alice’s
IP addr
“I’m Alice”
Alice’s
IP addr
encrypted
password
46. 8: Network Security 8-46
Authentication: yet another try
Goal: avoid playback attack
Failures, drawbacks?
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
K (R)
A-B
Alice is live, and
only Alice knows
key to encrypt
nonce, so it must
be Alice!
47. 8: Network Security 8-47
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”
R
Bob computes
K (R)
A
-
“send me your public key”
KA
+
(K (R)) = R
A
-
KA
+
and knows only Alice
could have the private
key, that encrypted R
such that
(K (R)) = R
A
-
K
A
+
48. 8: Network Security 8-48
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
T
K (R)
-
Send me your public key
T
K
+
A
K (R)
-
Send me your public key
A
K
+
T
K (m)
+
T
m = K (K (m))
+
T
-
Trudy gets
sends m to Alice
encrypted with
Alice’s public key
A
K (m)
+
A
m = K (K (m))
+
A
-
R
49. 8: Network Security 8-49
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!
50. 8: Network Security 8-50
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
51. 8: Network Security 8-51
Secure e-mail
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.
Alice wants to send confidential e-mail, m, to Bob.
KS( )
.
KB( )
.
+
+ -
KS(m )
KB(KS )
+
m
KS
KS
KB
+
Internet
KS( )
.
KB( )
.
-
KB
-
KS
m
KS(m )
KB(KS )
+
52. 8: Network Security 8-52
Secure e-mail
Bob:
uses his private key to decrypt and recover KS
uses KS to decrypt KS(m) to recover m
Alice wants to send confidential e-mail, m, to Bob.
KS( )
.
KB( )
.
+
+ -
KS(m )
KB(KS )
+
m
KS
KS
KB
+
Internet
KS( )
.
KB( )
.
-
KB
-
KS
m
KS(m )
KB(KS )
+
53. 8: Network Security 8-53
Secure e-mail (continued)
• Alice wants to provide sender authentication
message integrity.
• Alice digitally signs message.
• sends both message (in the clear) and digital signature.
H( )
. KA( )
.
-
+ -
H(m )
KA(H(m))
-
m
KA
-
Internet
m
KA( )
.
+
KA
+
KA(H(m))
-
m
H( )
. H(m )
compare
54. 8: Network Security 8-54
Secure e-mail (continued)
• Alice wants to provide secrecy, sender authentication,
message integrity.
Alice uses three keys: her private key, Bob’s public
key, newly created symmetric key
H( )
. KA( )
.
-
+
KA(H(m))
-
m
KA
-
m
KS( )
.
KB( )
.
+
+
KB(KS )
+
KS
KB
+
Internet
KS
55. 8: Network Security 8-55
Pretty good privacy (PGP)
Internet e-mail encryption
scheme, de-facto standard.
uses symmetric key
cryptography, public key
cryptography, hash
function, and digital
signature as described.
provides secrecy, sender
authentication, integrity.
inventor, Phil Zimmerman,
was target of 3-year
federal investigation.
---BEGIN PGP SIGNED MESSAGE---
Hash: SHA1
Bob:My husband is out of town
tonight.Passionately yours,
Alice
---BEGIN PGP SIGNATURE---
Version: PGP 5.0
Charset: noconv
yhHJRHhGJGhgg/12EpJ+lo8gE4vB3mqJ
hFEvZP9t6n7G6m5Gw2
---END PGP SIGNATURE---
A PGP signed message:
56. 8: Network Security 8-56
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
57. 8: Network Security 8-57
Secure sockets layer (SSL)
provides transport layer security to any TCP-based
application using SSL services.
e.g., between Web browsers, servers for e-commerce (shttp)
security services:
server authentication, data encryption, client authentication
(optional)
TCP
IP
TCP enhanced with SSL
TCP
socket
Application
TCP
IP
TCP API
SSL sublayer
Application
SSL
socket
58. 8: Network Security 8-58
SSL: three phases
1. Handshake:
Bob establishes TCP
connection to Alice
authenticates Alice
via CA signed
certificate
creates, encrypts
(using Alice’s public
key), sends master
secret key to Alice
nonce exchange not
shown
decrypt using
KA
-
to get MS
create
Master
Secret
(MS)
59. 8: Network Security 8-59
SSL: three phases
2. Key Derivation:
Alice, Bob use shared secret (MS) to generate 4
keys:
EB: Bob->Alice data encryption key
EA: Alice->Bob data encryption key
MB: Bob->Alice MAC key
MA: Alice->Bob MAC key
encryption and MAC algorithms negotiable between
Bob, Alice
why 4 keys?
60. 8: Network Security 8-60
SSL: three phases
3. Data transfer
H( )
.
MB
b1b2b3 … bn
d
d H(d)
d H(d)
H( )
.
EB
TCP byte stream
block n bytes together
compute
MAC
encrypt d,
MAC, SSL
seq. #
SSL
seq. #
d H(d)
Type Ver Len
SSL record
format
encrypted using EB
unencrypted
61. 8: Network Security 8-61
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
62. 8: Network Security 8-62
IPsec: Network Layer Security
network-layer secrecy:
sending host encrypts the
data in IP datagram
TCP and UDP segments;
ICMP and SNMP
messages.
network-layer authentication
destination host can
authenticate source IP
address
two principal protocols:
authentication header
(AH) protocol
encapsulation security
payload (ESP) protocol
for both AH and ESP, source,
destination handshake:
create network-layer
logical channel called a
security association (SA)
each SA unidirectional.
uniquely determined by:
security protocol (AH or
ESP)
source IP address
32-bit connection ID
63. 8: Network Security 8-63
Authentication Header (AH) Protocol
provides source
authentication, data
integrity, no
confidentiality
AH header inserted
between IP header,
data field.
protocol field: 51
intermediate routers
process datagrams as
usual
AH header includes:
connection identifier
authentication data:
source- signed message
digest calculated over
original IP datagram.
next header field:
specifies type of data
(e.g., TCP, UDP, ICMP)
IP header data (e.g., TCP, UDP segment)
AH header
64. 8: Network Security 8-64
ESP Protocol
provides secrecy, host
authentication, data
integrity.
data, ESP trailer
encrypted.
next header field is in ESP
trailer.
ESP authentication
field is similar to AH
authentication field.
Protocol = 50.
IP header TCP/UDP segment
ESP
header
ESP
trailer
ESP
authent.
encrypted
authenticated
65. 8: Network Security 8-65
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
66. 8: Network Security 8-66
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
67. 8: Network Security 8-67
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
68. 8: Network Security 8-68
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, ki
IV
ki
IV
used to encrypt ith byte, di, in frame:
ci = di XOR ki
IV
IV and encrypted bytes, ci sent in frame
69. 8: Network Security 8-69
802.11 WEP encryption
IV
(per frame)
KS: 40-bit
secret
symmetric
key k1
IV
k2
IV
k3
IV
… kN
IV
kN+1
IV
… kN+1
IV
d1 d2 d3 … dN CRC1 … CRC4
c1 c2 c3 … cN cN+1 … cN+4
plaintext
frame data
plus CRC
key sequence generator
( for given KS, IV)
802.11
header
IV
WEP-encrypted data
plus CRC
Figure 7.8-new1: 802.11 WEP protocol
Sender-side WEP encryption
70. 8: Network Security 8-70
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 ki
IV
Trudy knows ci di, so can compute ki
IV
Trudy knows encrypting key sequence k1
IV
k2
IV
k3
IV
…
Next time IV is used, Trudy can decrypt!
71. 8: Network Security 8-71
802.11i: improved security
numerous (stronger) forms of encryption
possible
provides key distribution
uses authentication server separate from
access point
72. 8: Network Security 8-72
AP: access point AS:
Authentication
server
wired
network
STA:
client station
1 Discovery of
security capabilities
3
STA and AS mutually authenticate, together
generate Master Key (MK). AP servers as “pass through”
2
3 STA derives
Pairwise Master
Key (PMK)
AS derives
same PMK,
sends to AP
4 STA, AP use PMK to derive
Temporal Key (TK) used for message
encryption, integrity
802.11i: four phases of operation
73. 8: Network Security 8-73
wired
network
EAP TLS
EAP
EAP over LAN (EAPoL)
IEEE 802.11
RADIUS
UDP/IP
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)
74. 8: Network Security 8-74
Chapter 8 roadmap
8.1 What is network security?
8.2 Principles of cryptography
8.3 Message integrity
8.4 End point authentication
8.5 Securing e-mail
8.6 Securing TCP connections: SSL
8.7 Network layer security: IPsec
8.8 Securing wireless LANs
8.9 Operational security: firewalls and IDS
75. 8: Network Security 8-75
Firewalls
isolates organization’s internal net from larger
Internet, allowing some packets to pass, blocking
others.
firewall
administered
network
public
Internet
firewall
76. 8: Network Security 8-76
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)
three types of firewalls:
stateless packet filters
stateful packet filters
application gateways
77. 8: Network Security 8-77
Stateless packet filtering
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
Should arriving
packet be allowed
in? Departing packet
let out?
78. 8: Network Security 8-78
Stateless packet filtering: example
example 1: block incoming and outgoing
datagrams with IP protocol field = 17 and with
either source or dest port = 23.
all incoming, 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.
79. 8: Network Security 8-79
Policy Firewall Setting
No outside Web access. Drop all outgoing packets to any IP
address, port 80
No incoming TCP connections,
except those for institution’s
public Web server only.
Drop all incoming TCP SYN packets to
any IP except 130.207.244.203, port
80
Prevent Web-radios from eating
up the available bandwidth.
Drop all incoming UDP packets - except
DNS and router broadcasts.
Prevent your network from being
used for a smurf DoS attack.
Drop all ICMP packets going to a
“broadcast” address (eg
130.207.255.255).
Prevent your network from being
tracerouted
Drop all outgoing ICMP TTL expired
traffic
Stateless packet filtering: more examples
80. 8: Network Security 8-80
action
source
address
dest
address
protocol
source
port
dest
port
flag
bit
allow 222.22/16
outside of
222.22/16
TCP > 1023 80
any
allow outside of
222.22/16
222.22/16
TCP 80 > 1023 ACK
allow 222.22/16
outside of
222.22/16
UDP > 1023 53 ---
allow outside of
222.22/16
222.22/16
UDP 53 > 1023 ----
deny all all all all all all
Access Control Lists
ACL: table of rules, applied top to bottom to
incoming packets: (action, condition) pairs
81. 8: Network Security 8-81
Stateful packet filtering
stateless packet filter: heavy handed tool
admits packets that “make no sense,” e.g., dest port =
80, ACK bit set, even though no TCP connection
established:
action
source
address
dest
address
protocol
source
port
dest
port
flag
bit
allow outside of
222.22/16
222.22/16
TCP 80 > 1023 ACK
stateful packet filter: track status of every TCP
connection
track connection setup (SYN), teardown (FIN): can
determine whether incoming, outgoing packets “makes sense”
timeout inactive connections at firewall: no longer admit
packets
82. 8: Network Security 8-82
action
source
address
dest
address
proto
source
port
dest
port
flag
bit
check
conxion
allow 222.22/16
outside of
222.22/16
TCP > 1023 80
any
allow outside of
222.22/16
222.22/16
TCP 80 > 1023 ACK x
allow 222.22/16
outside of
222.22/16
UDP > 1023 53 ---
allow outside of
222.22/16
222.22/16
UDP 53 > 1023 ----
x
deny all all all all all all
Stateful packet filtering
ACL augmented to indicate need to check
connection state table before admitting packet
83. 8: Network Security 8-83
Application gateways
filters packets on
application data as well
as on IP/TCP/UDP fields.
example: allow select
internal users to telnet
outside.
host-to-gateway
telnet session
gateway-to-remote
host telnet session
application
gateway
router and filter
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.
84. 8: Network Security 8-84
Limitations of firewalls and gateways
IP spoofing: router
can’t know if data
“really” comes from
claimed source
if multiple app’s. need
special treatment, each
has own app. gateway.
client software must
know how to contact
gateway.
e.g., must set IP address
of proxy in Web
browser
filters often use all or
nothing policy for UDP.
tradeoff: degree of
communication with
outside world, level of
security
many highly protected
sites still suffer from
attacks.
85. 8: Network Security 8-85
Intrusion detection systems
packet filtering:
operates on TCP/IP headers only
no correlation check among sessions
IDS: intrusion detection system
deep packet inspection: look at packet contents
(e.g., check character strings in packet against
database of known virus, attack strings)
examine correlation among multiple packets
• port scanning
• network mapping
• DoS attack
86. 8: Network Security 8-86
Web
server
FTP
server
DNS
server
application
gateway
Internet
demilitarized
zone
internal
network
firewall
IDS
sensors
Intrusion detection systems
multiple IDSs: different types of checking
at different locations
87. 8: Network Security 8-87
Network Security (summary)
Basic techniques…...
cryptography (symmetric and public)
message integrity
end-point authentication
…. used in many different security scenarios
secure email
secure transport (SSL)
IP sec
802.11
Operational Security: firewalls and IDS