Elementary Cryptography Steven Bogaerts. Goal of Cryptography ● Ensure security of communication over insecure medium  Privacy (secrecy, confidentiality)

Slides:

Advertisements

Similar presentations

Cryptography Ch-1 prepared by: Diwan.

Advertisements

Using Cryptography to Secure Information. Overview Introduction to Cryptography Using Symmetric Encryption Using Hash Functions Using Public Key Encryption.

Making “Good” Encryption Algorithms

Cryptology Terminology and Early History. Cryptology Terms Cryptology –The science of concealing the meaning of messages and the discovery of the meaning.

CS 6262 Spring 02 - Lecture #7 (Tuesday, 1/29/2002) Introduction to Cryptography.

1 Digital certificates One concern with the public key approach: must ensure that you are encrypting to the correct person’s public key  Otherwise, you.

Network Management and Security

1 Day 04- Cryptography Acknowledgements to Dr. Ola Flygt of Växjö University, Sweden for providing the original slides.

EEC 693/793 Special Topics in Electrical Engineering Secure and Dependable Computing Lecture 5 Wenbing Zhao Department of Electrical and Computer Engineering.

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

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

Lecture 1 Overview.

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

Chapter 13: Electronic Commerce and Information Security Invitation to Computer Science, C++ Version, Fourth Edition SP09: Contains security section (13.4)

Encryption. Introduction Computer security is the prevention of or protection against –access to information by unauthorized recipients –intentional but.

3.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Traditional Symmetric-Key Ciphers.

Cryptography Week-6.

History and Background Part 1: Basic Concepts and Monoalphabetic Substitution CSCI 5857: Encoding and Encryption.

1 Introduction to Security and Cryptology Enterprise Systems DT211 Denis Manley.

Chapter 2 Basic Encryption and Decryption. csci5233 computer security & integrity 2 Encryption / Decryption encrypted transmission AB plaintext ciphertext.

Lecture 2 Overview.

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

CS 483 – SD SECTION BY DR. DANIYAL ALGHAZZAWI (1) Information Security.

Lec. 5 : History of Cryptologic Research II

Cryptography By, Anthony Lonigro & Valentine Mbah.

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.

Day 18. Concepts Plaintext: the original message Ciphertext: the transformed message Encryption: transformation of plaintext into ciphertext Decryption:

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.

Chapter 31 Cryptography And Network Security Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cryptography Wei Wu. Internet Threat Model Client Network Not trusted!!

Symmetric-Key Cryptography

Cryptography Chapter 7 Part 2 Pages 781 to 812. Symmetric Cryptography Secret Key Figure 7-10 on page 782 Key distribution problem – Secure courier Many.

R R R CSE870: Advanced Software Engineering: Cheng (Sp 2003)1 Encryption A Brief Overview.

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)

Classical Crypto By: Luong-Sorin VA, IMIT Dith Nimol, IMIT.

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

Traditional Symmetric-Key Ciphers

Computer Security Cryptography. Cryptography Now and Before  In the past – mainly used for confidentiality  Today –Still used for confidentiality –Data.

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

Computer Science and Engineering Computer System Security CSE 5339/7339 Lecture 3 August 26, 2004.

Introduction to Cryptology Fall Definitions Digital encryption techniques are used to protect data in two ways: to maintain privacy and to prove.

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

DATA & COMPUTER SECURITY (CSNB414) MODULE 3 MODERN SYMMETRIC ENCRYPTION.

CS 483 – SD SECTION BY DR. DANIYAL ALGHAZZAWI (2) Information Security.

Symmetric Cipher Model Plaintext input 1- encryption algorithm 2- secret key Encryption Cipher text output Cipher text input 1- Decryption algorithm 2-

Introduction to Cryptology Fall Definitions Digital encryption techniques are used to protect data in two ways: to maintain privacy and to prove.

Lecture 2 (Chapter 2) Classical Encryption Techniques Prepared by Dr. Lamiaa M. Elshenawy 1.

Computer Security (CS4800)

Lecture 3 Page 1 CS 236 Online Introduction to Cryptography CS 236 On-Line MS Program Networks and Systems Security Peter Reiher.

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

Lecture 2 Overview. Cryptography Secret writing – Disguised data cannot be read, modified, or fabricated easily – Feasibility of complexity for communicating.

1 Introduction CS 303 Algorithmic Number Theory and Cryptography Jeremy R. Johnson.

Chapter Two: Classic Cryptography

Computer Security By Rubel Biswas. Introduction History Terms & Definitions Symmetric and Asymmetric Attacks on Cryptosystems Outline.

Department of Computer Science Chapter 5 Introduction to Cryptography Semester 1.

Chapter 2 Basic Encryption and Decryption

Campbell R. Harvey Duke University and NBER

Security through Encryption

Traditional Symmetric-Key Ciphers

Presentation transcript:

Elementary Cryptography Steven Bogaerts

Goal of Cryptography ● Ensure security of communication over insecure medium  Privacy (secrecy, confidentiality)  Integrity ● Communicate even with possibility of adversaries

Approaches to Secure Communication ● Steganography  Hide message existence ● Cryptography  Hide message meaning

Childhood "Secret Codes"

Cryptosystem ● How does this help us accomplish our goals?  Privacy  Integrity

Security Failures ● Privacy failure  Intercept ● Integrity failure  Modify  Fabricate ● Block

So cryptography is, like, awesome. But how is it done?

Encryption Algorithms ● Two categories:  Keyless  Keyed ● Symmetric ● Asymmetric ● Character representation  A=0, B=1,..., Z=25  So A + 3 = D, etc.

Substitution Ciphers ● Replace each letter with another ● Caesar cipher  c i = E(p i ) = p i + 3  Ex: THE EAGLE HAS LANDED wkh hdjoh kdv odqghg  Easy to memorize  In general: c i = E(p i ) = p i + n

Other Substitution Ciphers ● Key: "professional" ABCDEFGHIJKLMNOPQRSTUVWXYZ profesinalbcdghjkmqtuvwxyz ● Every third letter ABCDEFGHIJKLMNOPQRSTUVWXYZ adgjmpsvybehknqtwzcfilorux

Cryptanalysis ● Brute force: 26! possibilities ● Hints:  Frequencies: ● Letter (general) E, T, A, O, N, I, R,... ● First letter ● Last letter  Guesses at message content ● Double letter ● Digraphs, trigraphs ● Small words

Cryptanalysis ● Example: wklv phvvdjh lv qrw wrr kdug wr euhdn

Cryptanalysis ● Example: wklv phvvdjh lv qrw wrr kdug wr euhdn ● wrr --> see, too, add, odd, off... wr --> to, of Best guess: w = T, r = O

Cryptanalysis ● Example: wklv phvvdjh lv qrw wrr kdug wr euhdn ● wrr --> see, too, add, odd, off... wr --> to, of Best guess: w = T, r = O ● lv --> so, is, in,... T_SO very unlikely... T_IS likely Best guess: l = I, v = S

Cryptanalysis ● Example: wklv phvvdjh lv qrw wrr kdug wr euhdn ● wrr --> see, too, add, odd, off... wr --> to, of Best guess: w = T, r = O ● lv --> so, is, in,... T_SO very unlikely... T_IS likely Best guess: l = I, v = S ● wklv phvvdjh lv qrw wrr kdug wr euhdn T-IS --SS--- IS -OT TOO

Cryptanalysis wklv phvvdjh lv qrw wrr kdug wr euhdn THIS MESSAGE IS NOT TOO HARD TO BREAK ● Regularity ● Outside information

Cryptanalysis wklv phvvdjh lv qrw wrr kdug wr euhdn THIS MESSAGE IS NOT TOO HARD TO BREAK ● Regularity ● Outside information ● WWII: af to be target of a major assault  "Damaged" water distillery

One-Time Pad ● Avoid regularity ● Vernam Cipher example Key: CIHJTFDJZMEPQLFHXYRLS... Plaintext: HELLO CIHJT HELLO = 33 mod 26 Ciphertext: J M S U H Remaining key: FDJZMEPQLFHXYRLS...

One-Time Pad ● Hard to maintain keys ● Facilitate key distribution  Novel  Phone book

Transposition ● (Substitution - replace one letter with another) ● Transposition - mix up plaintext message  Columnar

Transposition ● (Substitution - replace one letter with another) ● Transposition - mix up plaintext message  Columnar: T A L L C O M P U T E R S C I E N T I S T S R O C K x k g j --> tmsicapcskluitxlteskcenrgortoj

Much More To Discuss... ● What makes a "good" encryption algorithm ● Data Encryption Standard (DES)  Double and Triple DES ● Advanced Encryption Standard (AES) ● Public Key Encryption  Rivest-Shamir-Adelman (RSA)

Summary So Far ● Maintain privacy, integrity despite adversaries ● Cryptosystems  Substitution  Transposition ● Cryptanalysis

Bible Codes? ● Equidistant Letter Sequences (ELS) ● Rips, Witztum in Statistical Science  Reviewers not convinced, but nothing formally wrong

Bible Codes? ● Refutations  McKay, Bar-Natan, Kalai, Bar-Hillel in Statistical Science  Moby Dick "predicts" assassinations

Scripture ● "... Ask and it will be given to you; seek and you will find; knock and the door will be opened to you." (Luke 11:9) ● "...the counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you." (John 14:26) ● "The secret things belong to the LORD our God, but the things revealed belong to us and to our children forever, that we may follow all the words of this law." (Deuteronomy 29:29)