Cryptography Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) Coming up: Cryptography 11.

Slides:



Advertisements
Similar presentations
Cryptography encryption authentication digital signatures
Advertisements

Using Cryptography to Secure Information. Overview Introduction to Cryptography Using Symmetric Encryption Using Hash Functions Using Public Key Encryption.
Public Key Encryption Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) Coming up: Public.
Computer Science CSC 474By Dr. Peng Ning1 CSC 474 Information Systems Security Topic 2.1 Introduction to Cryptography.
Management Information Systems Lection 05 Coding and encryption CLARK UNIVERSITY College of Professional and Continuing Education (COPACE)
Cryptography. 2 Objectives Explain common terms used in the field of cryptography Outline what mechanisms constitute a strong cryptosystem Demonstrate.
Andy’s Basic Crypto Course (ABC) Part 1 - Introduction.
CS 555Topic 11 Cryptography CS 555 Topic 1: Overview of the Course & Introduction to Encryption.
Intro To Encryption Exercise 1. Monoalphabetic Ciphers Examples:  Caesar Cipher  At Bash  PigPen (Will be demonstrated)  …
1 Foundations The problem of providing secret communication over insecure media is the most traditional and basic problem of cryptography.
CS426Fall 2010/Lecture 21 Computer Security CS 426 Lecture 2 Cryptography: Terminology & Classic Ciphers.
Ciphers Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) Coming up: What is Good Encryption?
CS526Topic 2: Classical Cryptography1 Information Security CS 526 Topic 2 Cryptography: Terminology & Classic Ciphers.
Chapter 2 – Classical Encryption Techniques
Encryption. Introduction Computer security is the prevention of or protection against –access to information by unauthorized recipients –intentional but.
Lecture 19 Page 1 CS 111 Online Security for Operating Systems: Cryptography, Authentication, and Protecting OS Resources CS 111 On-Line MS Program Operating.
Cryptography Week-6.
Cryptanalysis. The Speaker  Chuck Easttom  
CS5204 – Fall Cryptographic Security Presenter: Hamid Al-Hamadi October 13, 2009.
1 Cryptography Basics. 2 Cryptography Basic terminologies Symmetric key encryption Asymmetric key encryption Public Key Infrastructure Digital Certificates.
Chapter 2 Basic Encryption and Decryption. csci5233 computer security & integrity 2 Encryption / Decryption encrypted transmission AB plaintext ciphertext.
Lecture 2 Overview.
CIS 5371 Cryptography Introduction.
Security in Computing Cryptography (Introduction) Derived from Greek words: ‘Kruptos’ (hidden) and ‘graphein’ (writing.
Access Control Policies Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) 11 Coming up:
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.
Public Key Encryption and the RSA Public Key Algorithm CSCI 5857: Encoding and Encryption.
Cryptography, Authentication and Digital Signatures
Based on Applied Cryptography by Schneier Chapter 1: Foundations Dulal C. Kar.
Cryptography and Network Security (CS435) Part Two (Classic Encryption Techniques)
Network Security Section 1: Introduction to security.
CIT 380: Securing Computer SystemsSlide #1 CIT 380: Securing Computer Systems Classical Cryptography.
ITMS – 3153 Information Systems Security
1 Chapter 2-1 Conventional Encryption Message Confidentiality.
Network Security Lecture 11 Presented by: Dr. Munam Ali Shah.
Network Security Lecture 10 Presented by: Dr. Munam Ali Shah.
Encryption.
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)
Modes of Usage Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) 11 Coming up: Modes of.
Computer Security Cryptography. Cryptography Now and Before  In the past – mainly used for confidentiality  Today –Still used for confidentiality –Data.
Data Security and Encryption (CSE348) 1. Lecture # 3 2.
CRYPTOGRAPHY. TOPICS OF SEMINAR Introduction & Related Terms Categories and Aspects of cryptography Model of Network Security Encryption Techniques Public.
CRYPTOGRAPHY & NETWORK SECURITY Introduction and Basic Concepts Eng. Wafaa Kanakri Computer Engineering Umm Al-Qura University.
15-499Page :Algorithms and Applications Cryptography I – Introduction – Terminology – Some primitives – Some protocols.
NEW DIRECTIONS IN CRYPTOGRAPHY Made Harta Dwijaksara, Yi Jae Park.
Computer Science and Engineering Computer System Security CSE 5339/7339 Lecture 3 August 26, 2004.
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.
1 CIS 5371 Cryptography 1.Introduction. 2 Prerequisites for this course  Basic Mathematics, in particular Number Theory  Basic Probability Theory 
Discrete Mathematical Structures: Theory and Applications 1 Cryptography (advanced extra curricular topic)  Cryptography (from the Greek words Kryptos,
CHAOS CRYPTOGRAPHY Nathaniel Speiser Physics
CSCI 391: Practical Cryptology Introduction. Definitions Digital encryption techniques are used to protect data in two ways: to maintain privacy and to.
Lecture 3 Page 1 CS 236 Online Introduction to Cryptography CS 236 On-Line MS Program Networks and Systems Security Peter Reiher.
Lecture 2 Overview. Cryptography Secret writing – Disguised data cannot be read, modified, or fabricated easily – Feasibility of complexity for communicating.
CHAPTER 14 ENCRYPTION AND DECRYPTION Sajina Pradhan
@Yuan Xue CS 285 Network Security Cryptography Overview and Classical Encryption Algorithms Fall 2012 Yuan Xue.
1 CIS 5371 Cryptography 1.Introduction. 2 Prerequisites for this course  Basic Mathematics, in particular Number Theory  Basic Probability Theory 
CRYPTOGRAPHY Cryptography is art or science of transforming intelligible message to unintelligible and again transforming that message back to the original.
CRYPTOGRAPHY G REEK WORD MEANING “ SECRET WRITING ”
Chapter 2 Basic Encryption and Decryption
Introduction Of System Security
CSCI-235 Micro-Computer Applications
مروري برالگوريتمهاي رمز متقارن(كليد پنهان)
Classical Ciphers – I Terminology CSCI284 Spring 2004 GWU Shift Cipher
Computer Security Chapter Two
Basics Of Symmetric Encryption
Cryptanalysis Network Security.
Presentation transcript:

Cryptography Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) Coming up: Cryptography 11

Cryptography Apply your cryptanalytic skills. How do you get started? What questions should you ask? What is the likely underlying language of the plaintext? What characteristics of the probable source text are relevant? What characteristics of the source language are relevant? What is the likely nature/complexity of the encryption algorithm? Have any transformations/compressions been applied prior to encryption? What else? CIA Kryptos Sculpture Coming up: Encryption / Decryption 22

Encryption / Decryption The purpose of encryption is to render the message less useful / meaningful to any eavesdropper. Conceptually, the process of encryption is quite simple: As is the process of decryption: Encrypt ciphertext plaintext Key e (optional) Decrypt plaintext ciphertext Key d (optional) Coming up: Information Theory and Cryptography 33

Information Theory and Cryptography Information theory informs cryptography in several ways: What effect does encrypting a message have on the information content of the file? An attempt to decrypt a message is really an attempt to recover a message from a (systematically) noisy channel. How can redundancy in the source give clues to the decoding process? Is a perfect encryption possible (i.e., one that is theoretically unbreakable)? Coming up: Some Terminology 44

Some Terminology Encryption and decryption are functions which transform one text into another. In functional notation: C = E(P) and P = D(C) where C denotes ciphertext, E is the encryption rule, D is the decryption rule, P is the plaintext. In this case, we also have: P = D(E(P)) It is obviously important to be able to recover the original message from the ciphertext. Coming up: Keyed Algorithms 55

Keyed Algorithms Often the encryption and decryption algorithms use a key K. The key selects a specific algorithm from the family of algorithms defined by E. We write this dependence as: C = E(P,K E ) and P = D(C,K D ) If K E = K D, then the algorithm is called symmetric. If not, then it is called asymmetric. In general, P = D(E(P,K E ),K D ) An algorithm that does not use a key is called a keyless cipher. Coming up: Some Notation 66

Some Notation Often the notation E(P,K) and D(C,K) becomes cumbersome. An alternative notation is often used, particularly in cryptographic protocols. We’ll often use to denote E(P,K), and sometimes to denote D(P,K). For example, This is usually appropriate since, in many important commercial cryptosystems, the same algorithm is used for both encryption and decryption (i.e., the algorithm is its own inverse). Coming up: Cryptanalysis Tools 77

Cryptanalysis Tools The analyst works with: encrypted messages, known encryption algorithms, intercepted plaintext, data items known or suspected to be in a ciphertext message, mathematical and statistical tools and techniques, properties of languages, computers, ingenuity and luck. Really! CIA revealed that their analyst David Stein had also solved the same sections in 1998, using pencil and paper techniques, though at the time of his solution the information was only disseminated within the intelligence community, and no public announcement was made. -Wikipedia Coming up: Lessons 88

Lessons Encryption is designed to obscure the meaning of text. Redundancy is the enemy of secure encryption because it provides leverage to the attacker. End of presentation 99