1 Foundations The problem of providing secret communication over insecure media is the most traditional and basic problem of cryptography.

Slides:

Advertisements

Similar presentations

Chapter 3 Public Key Cryptography and Message authentication.

Advertisements

ECE454/CS594 Computer and Network Security Dr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2011.

Topic 7: Using cryptography in mobile computing. Cryptography basics: symmetric, public-key, hash function and digital signature Cryptography, describing.

Computer Science CSC 474By Dr. Peng Ning1 CSC 474 Information Systems Security Topic 2.1 Introduction to Cryptography.

1 Introduction CSE 5351: Introduction to cryptography Reading assignment: Chapter 1 of Katz & Lindell.

Principles of Information Security, 2nd edition1 Cryptography.

Web Security for Network and System Administrators1 Chapter 4 Encryption.

Lesson Title: Introduction to Cryptography Dale R. Thompson Computer Science and Computer Engineering Dept. University of Arkansas

TCP/IP Protocol Suite 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 29 Cryptography and Network.

First Edition by William Stallings and Lawrie Brown Lecture slides by Lawrie Brown and edited by Archana Chidanandan Cryptographic Tools.

CMSC 414 Computer and Network Security Lecture 3 Jonathan Katz.

McGraw-Hill©The McGraw-Hill Companies, Inc., Security PART VII.

Introduction to Symmetric Block Cipher Jing Deng Based on Prof. Rick Han’s Lecture Slides Dr. Andreas Steffen’s Security Tutorial.

Cryptography April 20, 2010 MIS 4600 – MBA © Abdou Illia.

Overview of Cryptography and Its Applications Dr. Monther Aldwairi New York Institute of Technology- Amman Campus INCS741: Cryptography.

Ref: STAL03More Concepts of Cryptography and Cryptanalysis 1 Reference –William Stallings, Cryptography and Network Security, 3rd Edition, Prentice Hall.

CS426Fall 2010/Lecture 21 Computer Security CS 426 Lecture 2 Cryptography: Terminology & Classic Ciphers.

CS526Topic 2: Classical Cryptography1 Information Security CS 526 Topic 2 Cryptography: Terminology & Classic Ciphers.

Applied Cryptography Chapter 1 Foundations Jaewon Lee.

Network Security Chapter

Lecture 4 Cryptographic Tools (cont) modified from slides of Lawrie Brown.

Chapter 2 – Classical Encryption Techniques

Encryption is a way to transform a message so that only the sender and recipient can read, see or understand it. The mechanism is based on the use of.

1 Chapter 4 Encryption. 2 Objectives In this chapter, you will: Learn the basics of encryption technology Recognize popular symmetric encryption algorithms.

©Brooks/Cole, 2003 Chapter 16 Security. ©Brooks/Cole, 2003 Define four aspects of security in a network: privacy, authentication, integrity, and nonrepudiation.

© Neeraj Suri EU-NSF ICT March 2006 DEWSNet Dependable Embedded Wired/Wireless Networks MUET Jamshoro Computer Security: Principles and Practice Slides.

CIS 5371 Cryptography Introduction.

Symmetric and Asymmetric Ciphers. Symmetric Encryption  or conventional / private-key / single-key  sender and recipient share a common key  all classical.

Chapter 1 Introduction Cryptography-Principles and Practice Harbin Institute of Technology School of Computer Science and Technology Zhijun Li

Network Security. Security Threats 8Intercept 8Interrupt 8Modification 8Fabrication.

Chapter 2 – Elementary Cryptography  Concepts of encryption  Cryptanalysis  Symmetric (secret key) Encryption (DES & AES)(DES & AES)  Asymmetric (public.

每时每刻可信安全 1The DES algorithm is an example of what type of cryptography? A Secret Key B Two-key C Asymmetric Key D Public Key A.

CSCE 201 Introduction to Information Security Fall 2010 Data Protection.

Introduction to Computer and Network Security Iliano Cervesato 24 August 2008 – Introduction to Cryptography.

Based on Applied Cryptography by Schneier Chapter 1: Foundations Dulal C. Kar.

1 Chapter 2-1 Conventional Encryption Message Confidentiality.

Network Security Lecture 11 Presented by: Dr. Munam Ali Shah.

CS526: Information Security Prof. Sam Wagstaff September 16, 2003 Cryptography Basics.

Module 3 – Cryptography Cryptography basics Ciphers Symmetric Key Algorithms Public Key Algorithms Message Digests Digital Signatures.

BASIC CRYPTOGRAPHIC CONCEPTS. Public Key Cryptography  Uses two keys for every simplex logical communication link.  Public key  Private key  The use.

Akademska in raziskovalna mreža Slovenije 1 Cryptography Overview Gorazd Božič Academic and Research Network of Slovenia

Cryptography Lynn Ackler Southern Oregon University.

Elementary Cryptography  Concepts of encryption  Symmetric (secret key) Encryption (DES & AES)(DES & AES)  Asymmetric (public key) Encryption (RSA)(RSA)

Computer Security: Principles and Practice First Edition by William Stallings and Lawrie Brown Lecture slides by Lawrie Brown Chapter 2 – Cryptographic.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Security.

CRYPTOGRAPHY. TOPICS OF SEMINAR Introduction & Related Terms Categories and Aspects of cryptography Model of Network Security Encryption Techniques Public.

Overview of Cryptography & Its Applications

24-Nov-15Security Cryptography Cryptography is the science and art of transforming messages to make them secure and immune to attacks. It involves plaintext,

15-499Page :Algorithms and Applications Cryptography I – Introduction – Terminology – Some primitives – Some protocols.

Textbook  Cryptography and Network Security: Principles and Practice (second/third edition) by William Stalling  密码学与网络安全：原理与实践（第 3 版） -- 刘玉珍等译电子工业出版社.

NEW DIRECTIONS IN CRYPTOGRAPHY Made Harta Dwijaksara, Yi Jae Park.

Lecture 23 Symmetric Encryption

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Security PART VII.

K. Salah1 Cryptography Module I. K. Salah2 Cryptographic Protocols  Messages should be transmitted to destination  Only the recipient should see it.

Intro to Cryptography Lesson Introduction

CRYPTOGRAPHY PRESENTED BY : NILAY JAYSWAL BRANCH : COMPUTER SCIENCE & ENGINEERING ENTRY NO. : 14BCS033 1.

INFORMATION SECURITY MANAGEMENT P ROTECTION M ECHANISMS - C RYPTOGRAPHY.

Computer Security Lecture 5 Ch.9 Public-Key Cryptography And RSA Prepared by Dr. Lamiaa Elshenawy.

1 CIS 5371 Cryptography 1.Introduction. 2 Prerequisites for this course  Basic Mathematics, in particular Number Theory  Basic Probability Theory 

Lecture 3 (Chapter 9) Public-Key Cryptography and RSA Prepared by Dr. Lamiaa M. Elshenawy 1.

INFORMATION SECURITY MANAGEMENT P ROTECTION M ECHANISMS - C RYPTOGRAPHY.

CS526Topic 2: Classical Cryptography1 Information Security CS 526 Topic 2 Cryptography: Terminology & Classic Ciphers.

CIM Cryptograhic Concepts Overview1 Cryptographic Concepts Overview Chapter 2- Cryptography and Network Security by Stallings for Details.

CMSC 414 Computer and Network Security Lecture 2 Jonathan Katz.

CRYPTOGRAPHY Cryptography is art or science of transforming intelligible message to unintelligible and again transforming that message back to the original.

Unit 2: Cryptography & Cryptographic Algorithm

Computer Security Chapter Two

Presentation transcript:

1 Foundations The problem of providing secret communication over insecure media is the most traditional and basic problem of cryptography.

2 ◎ Foundations Terminology: Sender vs. Receiver Messages vs. Encryption Encryption vs. Decryption Algorithms vs. Ciphers Symmetric alg. vs. Public-Key alg. Cryptanalysis Security of Cryptosystems Classical Cryptography vs. PKC EncryptionDecryption Plaintext Ciphertext Original Plaintext A cryptographic algorithm, also called a cipher, is the mathematical function used for encryption and decryption. To encrypt a plaintext message, apply an encryption algorithm to the plaintext. To decrypt a ciphertext, apply a decryption algorithm to the ciphertext.

3 ◎ Foundations E(P) = C D(C) = P, D( E(P) ) = P ; describe these terms P, C, E, D ? If the security of an algorithm is based on keeping the nature of the algorithm secret, it is called RESTRICTED(algorithm). encryption key decryption key There are two general forms of key-based algorithms: symmetric and public- key. Symmetric algorithms are algorithms where the encryption key can be calculated from the decryption key and vice versa. In many such systems, the encryption key and the decryption key are the same. VS.

4 ◎ Foundations secret-key alg, single-key PS. Symmetric algorithm are also called secret-key alg, single-key alg. or one-key alg. alg. or one-key alg.. Symmetric algotithms can also be divided into two categories: (a) stream algorithms or stream ciphers (b) block algorithms or block ciphers EncryptionDecryption Plaintext Ciphertext Original Plaintext EncryptionDecryption Plaintext Ciphertext Original Plaintext KEY Encryption KEY (public key) Decryption KEY (private key)

5 ◎ Foundations In this class, ALGORITHM will refer specifically to the MATHEMATICAL TRANSFORMATIONS for encryption and decryption. CRYPTOSYSTEMS will refer to the algorithm, plus the way in which it is implemented. There are three kinds of cryptographic functions: hash functions, secret key functions, and public key functions. We will describe what each kind is, and what it is useful for. Public key cryptography involves the use of two keys. Secret key cryptography involves the use of one key. Hash functions involve the use of zero keys ! Try to imagine what that could possibly mean, and what use it could possibly have --- an algorithm everyone knows with no secret key, and yet it has uses in security.

6 ◎ Foundations CRYPTANALSIS ：共有六種攻擊法，今依其難易度分成下述： (1) Ciphertext-only attack. Given ： Deduce ： Either ； or an algorithm to infer from (2) Known-plaintext attack. Given ： Deduce ： Either k, or an algorithm to infer from (3) Chosen-plaintext attack. Given ：同上； where the cryptanalysis choose Deduce ：同上

7 ◎ Foundations (4) Adaptive-chosen-plaintext attack. 動態選取明密文：由第一次選取而得之結果去決定第二次選取之明密文對（ pair ） (5)Chosen-ciphertext attack. 給予數對 “ 密文 → 明文 ” 而求出 key k (6) Chosen-key attack. This is not an attack when you are given the key. It is strange and obscure, not very practical.

8 ◎ Foundations Security of Cryptosystems All algorithms but one are theoretically breakable, given enough time and computing resources. If the time and money required to break an algorithm is more than the value of the encrypted data, then it is probably safe. An algorithm that is not breakable in practice is SECURE. Unconditionally secure VS. Computationally secure only a one-time pad is unbreakable given infinite resources(key 之長度大於明文長度 ). （針對前者而言，這種僅用一次法的 key 之管理成本高） The amount of computing time and power required to recover the encryption key is called the WORK FACTOR, and is expressed as an order of magnitude.

9 ◎ Foundations A cryptosystem is also called a CODE or a CIPHER. 參考資料： Substitution Ciphers & Transposition Cipher DES, Simple XOR 均屬於此種類別， P XOR K = C C XOR K = P ( P XOR K ) XOR K = P This cryptosystem is called a stream cipher which is a classical cryptosystem.

10 1. Foundations, including terminology and concepts of cryptography. 2. Cryptographic Protocols, including protocol build blocks (secure cryptographic module), basic protocols (key exchange, authentication, secret sharing, etc.), intermediate protocols (subliminal channel, group signature, key escrow, etc.), advanced protocols (zero-knowledge proofs, blind signature, oblivious transfer, etc.), esoteric( 奧秘的 ) protocols (secure elections, anonymous broadcast, digital cash, etc.).

11 3. Cryptographic Techniques, including key length, key management, and the using algorithms. 4. Cryptographic Algorithms, including mathematical backgrounds, DES and other block ciphers, one-way hash functions, public key cryptosystems. 5. Example Implementations, including some well-known commercial products and standards.