CCNA Security v2.0 Chapter 7: Cryptographic Systems.

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Transcript of CCNA Security v2.0 Chapter 7: Cryptographic Systems.

CCNA Security v2.0

Chapter 7:

Cryptographic Systems

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Chapter Outline

7.0 Introduction

7.1 Cryptographic Services

7.2 Basic Integrity and Authenticity

7.3 Confidentiality

7.4 Public Key Cryptography

7.5 Summary

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Section 7.1:Cryptographic Services

Upon completion of this section, you should be able to:

• Explain the requirements of secure communications including integrity, authentication, and confidentiality.

• Explain cryptography.

• Describe cryptoanalysis.

• Describe cryptology.

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Topic 7.1.1:Securing Communications

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Authentication, Integrity, and Confidentiality

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Authentication

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Data Integrity

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Data Confidentiality

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Topic 7.1.2:Cryptography

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Creating Ciphertext

Ciphertext can be creating using several methods:

• Transposition

• Substitution

• One-time pad

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Transposition Ciphers

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Substitution Ciphers

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One-Time Pad Ciphers

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Topic 7.1.3:Cryptanalysis

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Cracking Code

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Methods for Cracking Code

Methods used for cryptanalysis:

• Brute-force method

• Ciphertext method

• Known-Plaintext method

• Chosen-Plaintext method

• Chosen-Ciphertext method

• Meet-in-the-Middle method

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Methods for Cracking Code

Frequency Analysis of the English Alphabet

Deciphering Using Frequency Analysis

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Topic 7.1.4:Cryptology

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Making and Breaking Secret Codes

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Cryptanalysis

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The Secret is in the Keys

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Section 7.2:Basic Integrity and Authenticity

Upon completion of the section, you should be able to:

• Describe the purpose of cryptographic hashes.

• Explain how MD5 and SHA-1 are used to secure data communications.

• Describe authenticity with HMAC.

• Describe the components of key management.

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Topic 7.2.1:Cryptographic Hashes

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Cryptographic Hash Function

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Cryptographic Hash Function Properties

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Well-Known Hash Functions

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Topic 7.2.2:Integrity with MD5, SHA-1, and SHA-2

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Message Digest 5 Algorithm

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Secure Hash Algorithm

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MD5 Versus SHA

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Topic 7.2.3:Authenticity with HMAC

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Keyed-Hash Message Authentication Code

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HMAC Operation

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Hashing in Cisco Products

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Topic 7.2.4:Key Management

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Characteristics of Key Management

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Key Length and Keyspace

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The Keyspace

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Types of Cryptographic Keys

Types of cryptographic keys:

• Symmetric keys

• Asymmetric keys

• Digital signatures

• Hash keys

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Choosing Cryptographic Keys

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Section 7.3:Confidentiality

Upon completion of the section, you should be able to:

• Explain how encryption algorithms provide confidentiality.

• Explain the function of the DES, 3DES, and the AES algorithms .

• Describe the function of the Software Encrypted Algorithm (SEAL) and the Rivest ciphers (RC) algorithms.

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Topic 7.3.1:Encryption

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Two Classes of Encryption Algorithms

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Symmetric and Asymmetric Encryption

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Symmetric Encryption

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Symmetric Block Ciphers and Stream Ciphers

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Choosing an Encryption Algorithm

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Topic 7.3.2:Data Encryption Standard

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DES Symmetric Encryption

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DES Summary

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Improving DES with 3DES

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3DES Operation

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AES Origins

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AES Summary

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Topic 7.3.3:Alternate Encryption Algorithms

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Software-Optimized Encryption Algorithm (SEAL)

SEAL has several restrictions:

• The Cisco router and the peer must support IPsec.

• The Cisco router and the other peer must run an IOS image that supports encryption.

• The router and the peer must not have hardware IPsec encryption.

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RC Algorithms

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Topic 7.3.4:Diffie-Hellman Key Exchange

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Diffie-Hellman (DH) Algorithm

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DH Operation

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Section 7.4:Public Key Cryptography

Upon completion of the section, you should be able to:

• Explain the differences between symmetric and asymmetric encryptions and their intended applications.

• Explain the functionality of digital signatures.

• Explain the principles of a public key infrastructure (PKI).

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Topic 7.4.1:Symmetric Versus Asymmetric Encryption

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Asymmetric Key Algorithms

Four protocols that use asymmetric key algorithms:

• Internet Key Exchange (IKE)

• Secure Socket Layer (SSL)

• Secure Shell (SSH)

• Pretty Good Privacy (PGP)

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Public Key + Private Key = Confidentiality

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Private Key + Public Key = Authenticity

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Asymmetric AlgorithmsPlease use all 4Figs from this page with the Graphic titles as they tell a story. It may require 2 slides.

Alice Encrypts Message Using Bob’s Public Key

Alice Encrypts A Hash Using Bob’s Public Key

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Asymmetric AlgorithmsBob Uses Alice’s Public Key to Decrypt Hash

Bob Uses His Public Key to Decrypt Message

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Types of Asymmetric Algorithms

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Topic 7.4.2:Digital Signatures

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Using Digital Signatures

Digital Signature Properties:

• Signature is authentic

• Signature is unalterable

• Signature is not reusable

• Signature cannot be repudiated

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Code Signing

Digitally signing code provides several assurances about the code:

• The code is authentic and is actually sourced by the publisher.

• The code has not been modified since it left the software publisher.

• The publisher undeniably published the code.

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Digital Certificates

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Using Digital Certificates

Sending a Digital Certificate

Receiving a Digital Certificate

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Digital Signature Algorithms

DSA Scorecard

RSA Scorecard

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Topic 7.4.3:Public Key Infrastructure

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Public Key Infrastructure Overview

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PKI Framework

PKI Example

Elements of the PKI Framework

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Certificate Authorities

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Interoperability of Different PKI Vendors

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Public-Key Cryptography Standards

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Simple Certificate Enrollment Protocol

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PKI Topologies

Hierarchical CA

Cross Certified CA

Single-Root PKI Topology

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Registration Authority

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Digital Certificates and CAs

Retrieving CA Certificates

Submitting Certificate Requests to the CA

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Digital Certificates and CAs

Peers Authenticate Each Other

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Section 7.5:Summary

Chapter Objectives:

• Explain the areas of cryptology.

• Explain to two kinds of encryption algorithms.

Thank you.

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Instructor Resources

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