# CS155. Cryptography Overview

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 CS155 Cryptography Overview

2 Cryptography Is n A tremendous tool n The basis for many security mechanisms Is not n The solution to all security problems n Reliable unless implemented properly n Reliable unless used properly n Something you should try to invent or implement yourself

3 Kerckhoff s principle A cryptosystem should be secure even if everything about the system, except the secret key, is public knowledge.

4 Goal 1:secure communication Step 1: Session setup to exchange key Step 2: encrypt data

5 Goal 2: Protected files Disk Alice File 1 Alice File 2 No eavesdropping No tampering Analogous to secure communication: Alice today sends a message to Alice tomorrow

6 Symmetric Cryptography Assumes parties already share a secret key

7 Building block: sym. encryption Alice m, n E(k,m,n)=c E nonce Bob c, n D(k,c,n)=m D k k E, D: cipher k: secret key (e.g. 128 bits) m, c: plaintext, ciphertext n: nonce (aka IV) Encryption algorithm is publicly known Never use a proprietary cipher

8 Use Cases Single use key: (one time key) Key is only used to encrypt one message encrypted new key generated for every No need for nonce (set to 0) Multi use key: (many time key) Key used to encrypt multiple messages files: same key used to encrypt many files

9 First example: One Time Pad (single use key) Vernam (1917) Key: Plaintext: Ciphertext: Shannon 49: n OTP is secure against ciphertext-only attacks

10 Stream ciphers (single use key) Problem: OTP key is as long the message Solution: Pseudo random key -- stream ciphers key PRG c PRG(k) m message ciphertext Stream ciphers: RC4 (126 MB/sec), Salsa20/12 (643 MB/sec)

11 Dangers in using stream ciphers One time key!! Two time pad is insecure: C 1 m 1 PRG(k) C 2 m 2 PRG(k) Eavesdropper does: C 1 C 2 m 1 m 2 Enough redundant information in English that: m 1 m 2 m 1, m 2

12 Block ciphers: crypto work horse n Bits PT Block n Bits E, D CT Block Key k Bits Canonical examples: 1. 3DES: n= 64 bits, k = 168 bits 2. AES: n=128 bits, k = 128, 192, 256 bits IV handled as part of PT block

13 Building a block cipher Input: (m, k) Repeat simple mixing operation several times DES: Repeat 16 times: m L m R m R m L F(k,m R ) AES-128: Mixing step repeated 10 times Difficult to design: must resist subtle attacks differential attacks, linear attacks, brute-force,

14 Block Ciphers Built by Iteration key k key expansion k 1 k 2 k 3 k n m R(k 1, ) R(k 2, ) R(k 3, ) R(k n, ) c R(k,m): round function for DES (n=16), for AES-128 (n=10)

15 Incorrect use of block ciphers Electronic Code Book (ECB): PT: m 1 m 2 CT: c 1 c 2 Problem: n if m 1 =m 2 then c 1 =c 2

16 In pictures

17 Correct use of block ciphers I: CBC mode E a secure PRP. Cipher Block Chaining with random IV: IV m[0] m[1] m[2] m[3] E(k, ) E(k, ) E(k, ) E(k, ) IV c[0] c[1] c[2] c[3] ciphertext Q: how to do decryption?

18 Use cases: how to choose an IV Single use key: no IV needed (IV=0) Multi use key: (CPA Security) Best: use a fresh random IV for every message Can use unique IV (e.g counter) but then first step in CBC must be IV E(k 1,IV) benefit: may save transmitting IV with ciphertext

19 CBC with Unique IVs unique IV means: (k,iv) pair is used for only one message. generate unpredictable IV as E(k 1,IV) IV m[0] m[1] m[2] m[3] IV E(k 1, ) E(k, ) E(k, ) E(k, ) E(k, ) IV c[0] c[1] c[2] c[3] ciphertext

20 In pictures

21 Correct use of block ciphers II: CTR mode Counter mode with a random IV: (parallel encryption) IV m[0] m[1] E(k,IV) E(k,IV+1) m[l] E(k,IV+L) IV c[0] c[1] c[l] ciphertext Why are these modes secure? not today.

22 Performance: Crypto [ Wei Dai ] Intel Core 2 (on Windows Vista) Cipher Block/key size Speed (MB/sec) RC4 126 Salsa20/ DES 64/ AES/GCM 128/ AES is about 8x faster with AES-NI : Intel Westmere and onwards

23 Data integrity

24 Message Integrity: MACs Goal: message integrity. No confidentiality. n ex: Protecting public binaries on disk. k Message m tag k Alice Bob Generate tag: tag S(k, m) Verify tag:? V(k, m, tag) = `yes note: non-keyed checksum (CRC) is an insecure MAC!!

25 Secure MACs Attacker information: chosen message attack n for m 1,m 2,,m q attacker is given t i S(k,m i ) Attacker s goal: existential forgery. n produce some new valid message/tag pair (m,t). (m,t) { (m 1,t 1 ),, (m q,t q ) } A secure PRF gives a secure MAC: n S(k,m) = F(k,m) n V(k,m,t): `yes if t = F(k,m) and `no otherwise.

26 Construction 1: ECBC m[0] m[1] m[2] m[3] E(k, ) E(k, ) E(k, ) E(k, ) Raw CBC key = (k, k 1 ) E(k 1, ) tag

27 Construction 2: HMAC (Hash-MAC) Most widely used MAC on the Internet. H: hash function. example: SHA-256 ; output is 256 bits Building a MAC out of a hash function: Standardized method: HMAC S( k, m ) = H( kopad H( kipad m ))

28 SHA-256: Merkle-Damgard m[0] m[1] m[2] m[3] IV h h h h H(m) h(t, m[i]): compression function Thm 1: Thm 2 : if h is collision resistant then so is H if h is a PRF then HMAC is a PRF

29 Construction 3: PMAC parallel MAC ECBC and HMAC are sequential. PMAC: m[0] m[1] m[2] m[3] P(k,0) P(k,1) P(k,2) P(k,3) F(k, ) F(k, ) F(k, ) F(k, ) F(k 1, ) tag

30 Why are these MAC constructions secure? not today take CS255 Why the last encryption step in ECBC? n CBC (aka Raw-CBC) is not a secure MAC: n Given tag on a message m, attacker can deduce tag for some other message m n How: good crypto exercise

31 Authenticated Encryption: Encryption + MAC

32 Combining MAC and ENC (CCA) Encryption key K E Option 1: MAC-then-Encrypt (SSL) MAC(M,K I ) Msg M Msg M MAC MAC key = K I Enc K E Option 2: Encrypt-then-MAC (IPsec) Enc K E Secure for all secure primitives Msg M Option 3: Encrypt-and-MAC (SSH) Msg M Enc K E MAC(C, K I ) MAC MAC(M, K I ) MAC

33 OCB offset codebook mode More efficient authenticated encryption m[0] m[1] m[2] m[3] checksum P(N,k,0) P(N,k,1) P(N,k,2) P(N,k,3) P(N,k,0) E(k, ) E(k, ) E(k, ) E(k, ) E(k, ) P(N,k,0) P(N,k,1) P(N,k,2) P(N,k,3) auth c[0] c[1] c[2] c[3] c[4] Rogaway,

34 Public-key Cryptography

35 Public key encryption: (Gen, E, D) Gen pk sk m c c m E D

36 Applications Session setup (for now, only eavesdropping security) Alice Generate (pk, sk) x pk E(pk, x) Bob choose random x (e.g. 48 bytes) Non-interactive applications: (e.g. ) Bob sends to Alice encrypted using pk alice Note: Bob needs pk alice (public key management)

37 Applications Encryption in non-interactive settings: Encrypted File Systems write read sk A Alice Bob E(pk A, K F ) File E(k F, File) E(pk B, K F )

38 Applications Encryption in non-interactive settings: Key escrow: data recovery without Bob s key write Escrow Service sk escrow Bob E(pk escrow, K F ) E(k F, File) E(pk B, K F )

39 Trapdoor functions (TDF) Def: a trapdoor func. X Y is a triple of efficient algs. (G, F, F -1 ) G(): randomized alg. outputs key pair (pk, sk) F(pk, ): det. alg. that defines a func. X Y F -1 (sk, ): defines a func. Y X that inverts F(pk, ) Security: F(pk, ) is one-way without sk

40 Public-key encryption from TDFs (G, F, F -1 ): secure TDF X Y (E s, D s ) : symm. auth. encryption with keys in K H: X K a hash function We construct a pub-key enc. system (G, E, D): Key generation G: same as G for TDF

41 Public-key encryption from TDFs (G, F, F -1 ): secure TDF X Y (E s, D s ) : symm. auth. encryption with keys in K H: X K a hash function E( pk, m) : R x X, y F(pk, x) k H(x), c E s (k, m) output (y, c) D( sk, (y,c) ) : x F -1 (sk, y), k H(x), m D s (k, c) output m

42 In pictures: F(pk, x) E s ( H(x), m ) header body Security Theorem: If (G, F, F -1 ) is a secure TDF, (E s, D s ) provides auth. enc. and H: X K is a random oracle then (G,E,D) is CCA ro secure.

43 Digital Signatures Public-key encryption n Alice publishes encryption key n Anyone can send encrypted message n Only Alice can decrypt messages with this key Digital signature scheme n Alice publishes key for verifying signatures n Anyone can check a message signed by Alice n Only Alice can send signed messages

44 Digital Signatures from TDPs (G, F, F -1 ): secure TDP X X H: M X a hash function Sign( sk, m X) : output sig = F -1 (sk, H(m) ) Verify( pk, m, sig) : output 1 if H(m) = F(pk, sig) 0 otherwise Security: existential unforgeability under a chosen message attack (in the random oracle model)

45 Public-Key Infrastructure (PKI) Anyone can send Bob a secret message n Provided they know Bob s public key How do we know a key belongs to Bob? n If imposter substitutes another key, can read Bob s mail One solution: PKI n n n Trusted root Certificate Authority (e.g. Symantec) w Everyone must know the verification key of root CA w Check your browser; there are hundreds!! Root authority signs intermediate CA Results in a certificate chain

46 Back to SSL/TLS Version, Crypto choice, nonce Version, Choice, nonce, Signed certificate containing server s public key Ks C Secret key K encrypted with server s key Ks S switch to negotiated cipher Hash of sequence of messages Hash of sequence of messages data transmission

47 Limitations of cryptography Cryptography works when used correctly!! but is not the solution to all security problems XKCD 538

### Cryptography Overview

Cryptography Overview Cryptography Is n A tremendous tool n The basis for many security mechanisms Is not n The solution to all security problems n Reliable unless implemented properly n Reliable unless

### lundi 1 octobre 2012 In a set of N elements, by picking at random N elements, we have with high probability a collision two elements are equal

Symmetric Crypto Pierre-Alain Fouque Birthday Paradox In a set of N elements, by picking at random N elements, we have with high probability a collision two elements are equal N=365, about 23 people are

### Authenticated encryption

Authenticated encryption Dr. Enigma Department of Electrical Engineering & Computer Science University of Central Florida wocjan@eecs.ucf.edu October 16th, 2013 Active attacks on CPA-secure encryption

### Overview of Cryptographic Tools for Data Security. Murat Kantarcioglu

UT DALLAS Erik Jonsson School of Engineering & Computer Science Overview of Cryptographic Tools for Data Security Murat Kantarcioglu Pag. 1 Purdue University Cryptographic Primitives We will discuss the

### Symmetric Crypto MAC. Pierre-Alain Fouque

Symmetric Crypto MAC Pierre-Alain Fouque Birthday Paradox In a set of D elements, by picking at random D elements, we have with high probability a collision two elements are equal D=365, about 23 people

### Talk announcement please consider attending!

Talk announcement please consider attending! Where: Maurer School of Law, Room 335 When: Thursday, Feb 5, 12PM 1:30PM Speaker: Rafael Pass, Associate Professor, Cornell University, Topic: Reasoning Cryptographically

### Cryptographic hash functions and MACs Solved Exercises for Cryptographic Hash Functions and MACs

Cryptographic hash functions and MACs Solved Exercises for Cryptographic Hash Functions and MACs Enes Pasalic University of Primorska Koper, 2014 Contents 1 Preface 3 2 Problems 4 2 1 Preface This is a

### Cryptographic Hash Functions Message Authentication Digital Signatures

Cryptographic Hash Functions Message Authentication Digital Signatures Abstract We will discuss Cryptographic hash functions Message authentication codes HMAC and CBC-MAC Digital signatures 2 Encryption/Decryption

### Message Authentication Codes

2 MAC Message Authentication Codes : and Cryptography Sirindhorn International Institute of Technology Thammasat University Prepared by Steven Gordon on 28 October 2013 css322y13s2l08, Steve/Courses/2013/s2/css322/lectures/mac.tex,

### Network Security. Computer Networking Lecture 08. March 19, 2012. HKU SPACE Community College. HKU SPACE CC CN Lecture 08 1/23

Network Security Computer Networking Lecture 08 HKU SPACE Community College March 19, 2012 HKU SPACE CC CN Lecture 08 1/23 Outline Introduction Cryptography Algorithms Secret Key Algorithm Message Digest

### Authenticated Encryption: Relations among Notions and Analysis of the Generic Composition Paradigm By Mihir Bellare and Chanathip Namprempre

Authenticated Encryption: Relations among Notions and Analysis of the Generic Composition Paradigm By Mihir Bellare and Chanathip Namprempre Some slides were also taken from Chanathip Namprempre's defense

### CS 758: Cryptography / Network Security

CS 758: Cryptography / Network Security offered in the Fall Semester, 2003, by Doug Stinson my office: DC 3122 my email address: dstinson@uwaterloo.ca my web page: http://cacr.math.uwaterloo.ca/~dstinson/index.html

### 7! Cryptographic Techniques! A Brief Introduction

7! Cryptographic Techniques! A Brief Introduction 7.1! Introduction to Cryptography! 7.2! Symmetric Encryption! 7.3! Asymmetric (Public-Key) Encryption! 7.4! Digital Signatures! 7.5! Public Key Infrastructures

### Network Security. Gaurav Naik Gus Anderson. College of Engineering. Drexel University, Philadelphia, PA. Drexel University. College of Engineering

Network Security Gaurav Naik Gus Anderson, Philadelphia, PA Lectures on Network Security Feb 12 (Today!): Public Key Crypto, Hash Functions, Digital Signatures, and the Public Key Infrastructure Feb 14:

### Savitribai Phule Pune University

Savitribai Phule Pune University Centre for Information and Network Security Course: Introduction to Cyber Security / Information Security Module : Pre-requisites in Information and Network Security Chapter

### Chapter 8. Network Security

Chapter 8 Network Security Cryptography Introduction to Cryptography Substitution Ciphers Transposition Ciphers One-Time Pads Two Fundamental Cryptographic Principles Need for Security Some people who

### MAC. SKE in Practice. Lecture 5

MAC. SKE in Practice. Lecture 5 Active Adversary Active Adversary An active adversary can inject messages into the channel Active Adversary An active adversary can inject messages into the channel Eve

### CIS433/533 - Computer and Network Security Cryptography

CIS433/533 - Computer and Network Security Cryptography Professor Kevin Butler Winter 2011 Computer and Information Science A historical moment Mary Queen of Scots is being held by Queen Elizabeth and

### Message authentication and. digital signatures

Message authentication and " Message authentication digital signatures verify that the message is from the right sender, and not modified (incl message sequence) " Digital signatures in addition, non!repudiation

1 Introduction to Cryptography and Data Security 1 1.1 Overview of Cryptology (and This Book) 2 1.2 Symmetric Cryptography 4 1.2.1 Basics 4 1.2.2 Simple Symmetric Encryption: The Substitution Cipher...

### Overview of Public-Key Cryptography

CS 361S Overview of Public-Key Cryptography Vitaly Shmatikov slide 1 Reading Assignment Kaufman 6.1-6 slide 2 Public-Key Cryptography public key public key? private key Alice Bob Given: Everybody knows

### Lecture 9 - Network Security TDTS41-2006 (ht1)

Lecture 9 - Network Security TDTS41-2006 (ht1) Prof. Dr. Christoph Schuba Linköpings University/IDA Schuba@IDA.LiU.SE Reading: Office hours: [Hal05] 10.1-10.2.3; 10.2.5-10.7.1; 10.8.1 9-10am on Oct. 4+5,

### Introduction to Cryptography

Introduction to Cryptography Part 3: real world applications Jean-Sébastien Coron January 2007 Public-key encryption BOB ALICE Insecure M E C C D channel M Alice s public-key Alice s private-key Authentication

### Overview of Symmetric Encryption

CS 361S Overview of Symmetric Encryption Vitaly Shmatikov Reading Assignment Read Kaufman 2.1-4 and 4.2 slide 2 Basic Problem ----- ----- -----? Given: both parties already know the same secret Goal: send

### Authentication and Encryption: How to order them? Motivation

Authentication and Encryption: How to order them? Debdeep Muhopadhyay IIT Kharagpur Motivation Wide spread use of internet requires establishment of a secure channel. Typical implementations operate in

### IT Networks & Security CERT Luncheon Series: Cryptography

IT Networks & Security CERT Luncheon Series: Cryptography Presented by Addam Schroll, IT Security & Privacy Analyst 1 Outline History Terms & Definitions Symmetric and Asymmetric Algorithms Hashing PKI

### Provable-Security Analysis of Authenticated Encryption in Kerberos

Provable-Security Analysis of Authenticated Encryption in Kerberos Alexandra Boldyreva Virendra Kumar Georgia Institute of Technology, School of Computer Science 266 Ferst Drive, Atlanta, GA 30332-0765

### Network Security (2) CPSC 441 Department of Computer Science University of Calgary

Network Security (2) CPSC 441 Department of Computer Science University of Calgary 1 Friends and enemies: Alice, Bob, Trudy well-known in network security world Bob, Alice (lovers!) want to communicate

### EXAM questions for the course TTM4135 - Information Security May 2013. Part 1

EXAM questions for the course TTM4135 - Information Security May 2013 Part 1 This part consists of 5 questions all from one common topic. The number of maximal points for every correctly answered question

### Lecture 6 - Cryptography

Lecture 6 - Cryptography CSE497b - Spring 2007 Introduction Computer and Network Security Professor Jaeger www.cse.psu.edu/~tjaeger/cse497b-s07 Question 2 Setup: Assume you and I don t know anything about

### Outline. Computer Science 418. Digital Signatures: Observations. Digital Signatures: Definition. Definition 1 (Digital signature) Digital Signatures

Outline Computer Science 418 Digital Signatures Mike Jacobson Department of Computer Science University of Calgary Week 12 1 Digital Signatures 2 Signatures via Public Key Cryptosystems 3 Provable 4 Mike

### Authenticity of Public Keys

SSL/TLS EJ Jung 10/18/10 Authenticity of Public Keys Bob s key? private key Bob public key Problem: How does know that the public key she received is really Bob s public key? Distribution of Public Keys!

### Message Authentication Codes. Lecture Outline

Message Authentication Codes Murat Kantarcioglu Based on Prof. Ninghui Li s Slides Message Authentication Code Lecture Outline 1 Limitation of Using Hash Functions for Authentication Require an authentic

### CSE/EE 461 Lecture 23

CSE/EE 461 Lecture 23 Network Security David Wetherall djw@cs.washington.edu Last Time Naming Application Presentation How do we name hosts etc.? Session Transport Network Domain Name System (DNS) Data

### CS 161 Computer Security Spring 2010 Paxson/Wagner MT2

CS 161 Computer Security Spring 2010 Paxson/Wagner MT2 PRINT your name:, (last) SIGN your name: (first) PRINT your class account login: cs161- Your T s name: Your section time: Name of the person sitting

### CS3235 - Computer Security Third topic: Crypto Support Sys

Systems used with cryptography CS3235 - Computer Security Third topic: Crypto Support Systems National University of Singapore School of Computing (Some slides drawn from Lawrie Brown s, with permission)

### Lecture 9 - Message Authentication Codes

Lecture 9 - Message Authentication Codes Boaz Barak March 1, 2010 Reading: Boneh-Shoup chapter 6, Sections 9.1 9.3. Data integrity Until now we ve only been interested in protecting secrecy of data. However,

### Modes of Operation of Block Ciphers

Chapter 3 Modes of Operation of Block Ciphers A bitblock encryption function f: F n 2 Fn 2 is primarily defined on blocks of fixed length n To encrypt longer (or shorter) bit sequences the sender must

### Cryptosystems. Bob wants to send a message M to Alice. Symmetric ciphers: Bob and Alice both share a secret key, K.

Cryptosystems Bob wants to send a message M to Alice. Symmetric ciphers: Bob and Alice both share a secret key, K. C= E(M, K), Bob sends C Alice receives C, M=D(C,K) Use the same key to decrypt. Public

### Error oracle attacks and CBC encryption. Chris Mitchell ISG, RHUL http://www.isg.rhul.ac.uk/~cjm

Error oracle attacks and CBC encryption Chris Mitchell ISG, RHUL http://www.isg.rhul.ac.uk/~cjm Agenda 1. Introduction 2. CBC mode 3. Error oracles 4. Example 1 5. Example 2 6. Example 3 7. Stream ciphers

### Introduction to Computer Security

Introduction to Computer Security Hash Functions and Digital Signatures Pavel Laskov Wilhelm Schickard Institute for Computer Science Integrity objective in a wide sense Reliability Transmission errors

### Cryptography Lecture 8. Digital signatures, hash functions

Cryptography Lecture 8 Digital signatures, hash functions A Message Authentication Code is what you get from symmetric cryptography A MAC is used to prevent Eve from creating a new message and inserting

### Designing Hash functions. Reviewing... Message Authentication Codes. and message authentication codes. We have seen how to authenticate messages:

Designing Hash functions and message authentication codes Reviewing... We have seen how to authenticate messages: Using symmetric encryption, in an heuristic fashion Using public-key encryption in interactive

### Secure Sockets Layer

SSL/TLS provides endpoint authentication and communications privacy over the Internet using cryptography. For web browsing, email, faxing, other data transmission. In typical use, only the server is authenticated

### SECURITY IN NETWORKS

SECURITY IN NETWORKS GOALS Understand principles of network security: Cryptography and its many uses beyond confidentiality Authentication Message integrity Security in practice: Security in application,

### Message Authentication Code

Message Authentication Code Ali El Kaafarani Mathematical Institute Oxford University 1 of 44 Outline 1 CBC-MAC 2 Authenticated Encryption 3 Padding Oracle Attacks 4 Information Theoretic MACs 2 of 44

### Public Key Cryptography Overview

Ch.20 Public-Key Cryptography and Message Authentication I will talk about it later in this class Final: Wen (5/13) 1630-1830 HOLM 248» give you a sample exam» Mostly similar to homeworks» no electronic

### Network Security. Modes of Operation. Steven M. Bellovin February 3, 2009 1

Modes of Operation Steven M. Bellovin February 3, 2009 1 Using Cryptography As we ve already seen, using cryptography properly is not easy Many pitfalls! Errors in use can lead to very easy attacks You

### CPS 590.5 Computer Security Lecture 9: Introduction to Network Security. Xiaowei Yang xwy@cs.duke.edu

CPS 590.5 Computer Security Lecture 9: Introduction to Network Security Xiaowei Yang xwy@cs.duke.edu Previous lectures Worm Fast worm design Today Network security Cryptography building blocks Existing

### Authentication requirement Authentication function MAC Hash function Security of

UNIT 3 AUTHENTICATION Authentication requirement Authentication function MAC Hash function Security of hash function and MAC SHA HMAC CMAC Digital signature and authentication protocols DSS Slides Courtesy

### Using etoken for SSL Web Authentication. SSL V3.0 Overview

Using etoken for SSL Web Authentication Lesson 12 April 2004 etoken Certification Course SSL V3.0 Overview Secure Sockets Layer protocol, version 3.0 Provides communication privacy over the internet. Prevents

### Authentication, digital signatures, PRNG

Multimedia Security Authentication, digital signatures, PRNG Mauro Barni University of Siena Beyond confidentiality Up to now, we have been concerned with protecting message content (i.e. confidentiality)

### ETSI TS 102 176-2 V1.2.1 (2005-07)

TS 102 176-2 V1.2.1 (2005-07) Technical Specification Electronic Signatures and Infrastructures (ESI); Algorithms and Parameters for Secure Electronic Signatures; Part 2: Secure channel protocols and algorithms

### Dr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2010

CS 494/594 Computer and Network Security Dr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2010 1 Introduction to Cryptography What is cryptography?

### Network Security Technology Network Management

COMPUTER NETWORKS Network Security Technology Network Management Source Encryption E(K,P) Decryption D(K,C) Destination The author of these slides is Dr. Mark Pullen of George Mason University. Permission

### CSCE 465 Computer & Network Security

CSCE 465 Computer & Network Security Instructor: Dr. Guofei Gu http://courses.cse.tamu.edu/guofei/csce465/ Public Key Cryptogrophy 1 Roadmap Introduction RSA Diffie-Hellman Key Exchange Public key and

### Chapter 11 Security+ Guide to Network Security Fundamentals, Third Edition Basic Cryptography

Chapter 11 Security+ Guide to Network Security Fundamentals, Third Edition Basic Cryptography What Is Steganography? Steganography Process of hiding the existence of the data within another file Example:

### Chapter 10. Network Security

Chapter 10 Network Security 10.1. Chapter 10: Outline 10.1 INTRODUCTION 10.2 CONFIDENTIALITY 10.3 OTHER ASPECTS OF SECURITY 10.4 INTERNET SECURITY 10.5 FIREWALLS 10.2 Chapter 10: Objective We introduce

### Common Pitfalls in Cryptography for Software Developers. OWASP AppSec Israel July 2006. The OWASP Foundation http://www.owasp.org/

Common Pitfalls in Cryptography for Software Developers OWASP AppSec Israel July 2006 Shay Zalalichin, CISSP AppSec Division Manager, Comsec Consulting shayz@comsecglobal.com Copyright 2006 - The OWASP

### Cryptography and Network Security, PART IV: Reviews, Patches, and11.2012 Theory 1 / 53

Cryptography and Network Security, PART IV: Reviews, Patches, and Theory Timo Karvi 11.2012 Cryptography and Network Security, PART IV: Reviews, Patches, and11.2012 Theory 1 / 53 Key Lengths I The old

### CRYPTOGRAPHY IN NETWORK SECURITY

ELE548 Research Essays CRYPTOGRAPHY IN NETWORK SECURITY AUTHOR: SHENGLI LI INSTRUCTOR: DR. JIEN-CHUNG LO Date: March 5, 1999 Computer network brings lots of great benefits and convenience to us. We can

### Transport Level Security

Transport Level Security Overview Raj Jain Washington University in Saint Louis Saint Louis, MO 63130 Jain@cse.wustl.edu Audio/Video recordings of this lecture are available at: http://www.cse.wustl.edu/~jain/cse571-14/

### Information Security

SE 4472 / ECE 9064 Information Security Week 11: Transport Layer Security (TLS): Putting it all together Fall 2015 Prof. Aleksander Essex Security at the Transport Layer Where we started in this course:

### Hash Functions. Integrity checks

Hash Functions EJ Jung slide 1 Integrity checks Integrity vs. Confidentiality! Integrity: attacker cannot tamper with message! Encryption may not guarantee integrity! Intuition: attacker may able to modify

### Message authentication

Message authentication -- Hash based MAC unctions -- MAC unctions based on bloc ciphers -- Authenticated encryption (c) Levente Buttyán (buttyan@crysys.hu) Secret preix method MAC (x) = H( x) insecure!

### Security. Contents. S-72.3240 Wireless Personal, Local, Metropolitan, and Wide Area Networks 1

Contents Security requirements Public key cryptography Key agreement/transport schemes Man-in-the-middle attack vulnerability Encryption. digital signature, hash, certification Complete security solutions

### Part I. Universität Klagenfurt - IWAS Multimedia Kommunikation (VK) M. Euchner; Mai 2001. Siemens AG 2001, ICN M NT

Part I Contents Part I Introduction to Information Security Definition of Crypto Cryptographic Objectives Security Threats and Attacks The process Security Security Services Cryptography Cryptography (code

### Authentication applications Kerberos X.509 Authentication services E mail security IP security Web security

UNIT 4 SECURITY PRACTICE Authentication applications Kerberos X.509 Authentication services E mail security IP security Web security Slides Courtesy of William Stallings, Cryptography & Network Security,

### Overview. SSL Cryptography Overview CHAPTER 1

CHAPTER 1 Note The information in this chapter applies to both the ACE module and the ACE appliance unless otherwise noted. The features in this chapter apply to IPv4 and IPv6 unless otherwise noted. Secure

### Lecture 10: CPA Encryption, MACs, Hash Functions. 2 Recap of last lecture - PRGs for one time pads

CS 7880 Graduate Cryptography October 15, 2015 Lecture 10: CPA Encryption, MACs, Hash Functions Lecturer: Daniel Wichs Scribe: Matthew Dippel 1 Topic Covered Chosen plaintext attack model of security MACs

### Chapter 6 CDMA/802.11i

Chapter 6 CDMA/802.11i IC322 Fall 2014 Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Some material copyright 1996-2012 J.F Kurose and K.W. Ross,

### SAMPLE EXAM QUESTIONS MODULE EE5552 NETWORK SECURITY AND ENCRYPTION ECE, SCHOOL OF ENGINEERING AND DESIGN BRUNEL UNIVERSITY UXBRIDGE MIDDLESEX, UK

SAMPLE EXAM QUESTIONS MODULE EE5552 NETWORK SECURITY AND ENCRYPTION September 2010 (reviewed September 2014) ECE, SCHOOL OF ENGINEERING AND DESIGN BRUNEL UNIVERSITY UXBRIDGE MIDDLESEX, UK NETWORK SECURITY

### CIS 6930 Emerging Topics in Network Security. Topic 2. Network Security Primitives

CIS 6930 Emerging Topics in Network Security Topic 2. Network Security Primitives 1 Outline Absolute basics Encryption/Decryption; Digital signatures; D-H key exchange; Hash functions; Application of hash

### The Misuse of RC4 in Microsoft Word and Excel

The Misuse of RC4 in Microsoft Word and Excel Hongjun Wu Institute for Infocomm Research, Singapore hongjun@i2r.a-star.edu.sg Abstract. In this report, we point out a serious security flaw in Microsoft

### Practice Questions. CS161 Computer Security, Fall 2008

Practice Questions CS161 Computer Security, Fall 2008 Name Email address Score % / 100 % Please do not forget to fill up your name, email in the box in the midterm exam you can skip this here. These practice

### Chapter 7 Transport-Level Security

Cryptography and Network Security Chapter 7 Transport-Level Security Lectured by Nguyễn Đức Thái Outline Web Security Issues Security Socket Layer (SSL) Transport Layer Security (TLS) HTTPS Secure Shell

### Chapter 17. Transport-Level Security

Chapter 17 Transport-Level Security Web Security Considerations The World Wide Web is fundamentally a client/server application running over the Internet and TCP/IP intranets The following characteristics

### Lecture 9: Application of Cryptography

Lecture topics Cryptography basics Using SSL to secure communication links in J2EE programs Programmatic use of cryptography in Java Cryptography basics Encryption Transformation of data into a form that

### GCM-SIV: Full Nonce Misuse-Resistant Authenticated Encryption at Under One Cycle per Byte. Yehuda Lindell Bar-Ilan University

GCM-SIV: Full Nonce Misuse-Resistant Authenticated Encryption at Under One Cycle per Byte Shay Gueron Haifa Univ. and Intel Yehuda Lindell Bar-Ilan University Appeared at ACM CCS 2015 How to Encrypt with

### Message Authentication

Message Authentication message authentication is concerned with: protecting the integrity of a message validating identity of originator non-repudiation of origin (dispute resolution) will consider the

### 1. a. Define the properties of a one-way hash function. (6 marks)

1. a. Define the properties of a one-way hash function. (6 marks) A hash function h maps arbitrary length value x to fixed length value y such that: Hard to reverse. Given value y not feasible to find

### Client Server Registration Protocol

Client Server Registration Protocol The Client-Server protocol involves these following steps: 1. Login 2. Discovery phase User (Alice or Bob) has K s Server (S) has hash[pw A ].The passwords hashes are

### The Order of Encryption and Authentication for Protecting Communications (Or: How Secure is SSL?)

The Order of Encryption and Authentication for Protecting Communications (Or: How Secure is SSL?) Hugo Krawczyk Abstract. We study the question of how to generically compose symmetric encryption and authentication

### Network Security - ISA 656 Introduction to Cryptography

Network Security - ISA 656 Angelos Stavrou September 18, 2007 Codes vs. K = {0, 1} l P = {0, 1} m C = {0, 1} n, C C E : P K C D : C K P p P, k K : D(E(p, k), k) = p It is infeasible to find F : P C K Let

MACs Message authentication and integrity Foundations of Cryptography Computer Science Department Wellesley College Table of contents Introduction MACs Constructing Secure MACs Secure communication and

### HTTPS: Transport-Layer Security (TLS), aka Secure Sockets Layer (SSL)

CSCD27 Computer and Network Security HTTPS: Transport-Layer Security (TLS), aka Secure Sockets Layer (SSL) 11 SSL CSCD27 Computer and Network Security 1 CSCD27F Computer and Network Security 1 TLS (Transport-Layer

### Chapter 7: Network security

Chapter 7: Network security Foundations: what is security? cryptography authentication message integrity key distribution and certification Security in practice: application layer: secure e-mail transport

### Properties of Secure Network Communication

Properties of Secure Network Communication Secrecy: Only the sender and intended receiver should be able to understand the contents of the transmitted message. Because eavesdroppers may intercept the message,

### Secure Socket Layer. Introduction Overview of SSL What SSL is Useful For

Secure Socket Layer Secure Socket Layer Introduction Overview of SSL What SSL is Useful For Introduction Secure Socket Layer (SSL) Industry-standard method for protecting web communications. - Data encryption

### CryptoVerif Tutorial

CryptoVerif Tutorial Bruno Blanchet INRIA Paris-Rocquencourt bruno.blanchet@inria.fr November 2014 Bruno Blanchet (INRIA) CryptoVerif Tutorial November 2014 1 / 14 Exercise 1: preliminary definition SUF-CMA

### Cryptography & Network Security

Cryptography & Network Security Lecture 1: Introduction & Overview 2002. 3. 27 chlim@sejong.ac.kr Common Terms(1) Cryptography: The study of mathematical techniques related to aspects of information security

### Introduction to Cryptography CS 355

Introduction to Cryptography CS 355 Lecture 30 Digital Signatures CS 355 Fall 2005 / Lecture 30 1 Announcements Wednesday s lecture cancelled Friday will be guest lecture by Prof. Cristina Nita- Rotaru

### Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle. Network Security. Chapter 13

Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle Network Security Chapter 13 Some More Secure Channel Issues Outline In the course we have yet only seen catastrophic

### NXP & Security Innovation Encryption for ARM MCUs

NXP & Security Innovation Encryption for ARM MCUs Presenters Gene Carter- International Product Manager, NXP Semiconductors Gene is responsible for marketing of the ARM7 and Cortex-M3 microcontrollers.

### Massachusetts Institute of Technology Handout 13 6.857: Network and Computer Security October 9, 2003 Professor Ronald L. Rivest.

Massachusetts Institute of Technology Handout 13 6.857: Network and Computer Security October 9, 2003 Professor Ronald L. Rivest Quiz 1 1. This quiz is intended to provide a fair measure of your understanding

### Computer Networks 1 (Mạng Máy Tính 1) Lectured by: Dr. Phạm Trần Vũ MEng. Nguyễn CaoĐạt

Computer Networks 1 (Mạng Máy Tính 1) Lectured by: Dr. Phạm Trần Vũ MEng. Nguyễn CaoĐạt 1 Lecture 11: Network Security Reference: Chapter 8 - Computer Networks, Andrew S. Tanenbaum, 4th Edition, Prentice

### Cryptography and Network Security Chapter 15

Cryptography and Network Security Chapter 15 Fourth Edition by William Stallings Lecture slides by Lawrie Brown Chapter 15 Electronic Mail Security Despite the refusal of VADM Poindexter and LtCol North

### One-Way Encryption and Message Authentication

One-Way Encryption and Message Authentication Cryptographic Hash Functions Johannes Mittmann mittmann@in.tum.de Zentrum Mathematik Technische Universität München (TUM) 3 rd Joint Advanced Student School