# Symmetric Crypto MAC. Pierre-Alain Fouque

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 Symmetric Crypto MAC Pierre-Alain Fouque

2 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 are required Let two sets N and M of random elements in a large set D, the number of expected collisions is N M / D (Birthday paradox with boys and girls)

3 Message Authentication Code (MAC) Warning: Encryption does not provide integrity Eg: CTR mode ensures confidentiality if the blockcipher used is secure. However, no integrity is guaranteed. (CBC first block) Alice C 1 C 1 Bank M 1 = «\$200 on Bob s account» C 1 = (ctr) M 1 Eve M 1 = «\$2000 on Eve s account» C 1 = C 1 M 1 M 1

4 Definition of Message Authentication Code Key generation: randomized alg. output: key uniformly distributed Tag MAC generation: randomized or deterministic input: M {0,1} * output: tag τ {0,1}t : τ = M K ( M ) Verification: deterministic alg. input: tag τ {0,1} t and message M output: bit if the tag is valid for this message s.t. for any K and message M, if τ = M K ( M ), then V K (τ, M ) = 1

5 Security game Adversary s goals: 1. key recovery attacks 2. forgery: producing a valid MAC for some message M (of his choice, or any) Adversary s ressources: 1. known message attack: interception of MACs. Adv. knows pair (M, τ) of already tagged messages 2. chosen message attack: Adv. knows the tag of message of his choice (access to a MAC generation alg. adaptively or not)

6 Security game Def: Combining an adversary s goal and some ressources SUF-CMA: strongly inforgeability against chosen message attacks Challenger M i τ i (M, τ) 1 : valid tag Adversary A Adv ( A ) = Pr ( Expérience retourne 1)

7 Generic Security 1. For a t-bit MAC, advantage (forgery probability) is always at least 1/2 t 2. Among 2 t/2 MACs, by the birthday paradox, there is a collision between two of them: these collisions can be used to recover the keys...

8 MAC vs. Signature Signatures: used for vertifying public keys, guarantee non-repudiation, same properties than hand-written signature MACs: very good performences, secret-key shared between two users no non-repudiation, no public verification

9 First construction Let F : {0,1} k {0,1} * {0,1} t a random function (i.e. outputs are indistinguishable from random values) MAC construction: For message M = M 1 M m, τ = F K ( M 1 ) F K ( M m ) Is this scheme secure?

10 Second Example Let F : {0,1} k {0,1} * {0,1} t random function For message M = M 1 M m For i = 1 to m, y i = F K ( <i>, M i ) τ = y 1 y m Is this scheme secure?

11 unencrypted CBC-MAC C i = (M i C i-1 ) MAC = C m Secure only for constant length messages M 1 M 2 M m C 1 C 2 Mac = C m

12 Security CBC-MAC Let 2 arbitrary messages M and M M 1 M 2 M 3 MAC(M) is C 3 = Mac C 1 C 2 Mac = C 3 M 1 M 2 MAC(M ) is C 2 = Mac C 1 Mac = C 2

13 unencrypted CBC-MAC Given MACs of M and M, it is possible to forge MAC of another message M 1 M 2 M 3 M 1 Mac M 2 C 1 C 2 C 3 C 1 Mac =C 2 Recovering the secret key is in 2 k MAC computation where k is the bit length of the used key (exhaustive search)

14 No IV in CBC-MAC The integrity of the first block is not ensured if an IV is used IV M 1 M 2 M 1 IV IV IV M 2 C 1 Mac = C 2 C 1 Mac = C 2 ( M, IV, Mac ) ( M, IV, Mac ) 20

15 Encrypted CBC-MAC (EMAC) C i = (M i C i-1 ) and MAC = (C m ) Secure if less than 2 n/2 MACs are computed Keys can be recovered using 2 exhaustive search in time 2 k (for k-bit keys) M 1 M 2 M m C 1 C 2 C m Mac = C m+1

16 Hash-based MAC Consider the following MAC scheme: MAC K ( M ) = H ( K M ) Is it secure?

18 Encryption and Authentication IPSEC: MAC-Then-Encrypt SSL/TLS: Encrypt-Then-MAC SSH: MAC-And-Encrypt

19 Mac-And-Encrypt Non-secure mode of operation Confidentiality is not guaranteed Plaintext MAC contains information on the plaintext MAC Encryption MAC ciphertext

20 MAC-then-Encrypt Non-always secure but it could be In practice, one can construct secure scheme Plaintext MAC τ Encryption authenticated ciphertext

21 CCM: Mac-then-encrypt CCM proposed by Housley, Whiting and Ferguson Wifi network NIST in 2003, operation mode for AES CBC-MAC then CTR associated data security proof

22 CCM mode B[0] M[1] M[i-1] M[i] M[m] τ ctr ctr+1 ctr+i ctr+m τ M[1] M[i] M[m] C[0] C[1] C[i] C[m]

23 Encrypt-then-MAC Secure if the encryption mode is secure and if the MAC is secure Plaintext Encryption ciphertext MAC τ authenticated encryption

24 Encrypt-then-MAC IV M[1] M[i-1] M[i] M[m] C[0] C[1] C[i-1] C[i] C[m] τ

25 One-pass Mode Message is treated once: More efficient : near as efficient as one encryption One key Examples : IAPM, IACBC, OCB,

26 IACBC mode r M[1] M[m -1] Checksum S 1 S m-1 S m C[0] C[1] C[m -1] C[m]

### 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

### 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

### 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

### 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

### 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

### 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

### On the Security of CTR + CBC-MAC

On the Security of CTR + CBC-MAC NIST Modes of Operation Additional CCM Documentation Jakob Jonsson * jakob jonsson@yahoo.se Abstract. We analyze the security of the CTR + CBC-MAC (CCM) encryption mode.

### CS155. Cryptography Overview

CS155 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

### On the Security of the CCM Encryption Mode and of a Slight Variant

On the Security of the CCM Encryption Mode and of a Slight Variant Pierre-Alain Fouque 1 and Gwenaëlle Martinet 2 and Frédéric Valette 3 and Sébastien Zimmer 1 1 École normale supérieure, 45 rue d Ulm,

### 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,

### 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!

### Cryptography and Network Security Chapter 12

Cryptography and Network Security Chapter 12 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 12 Message Authentication Codes At cats' green on the Sunday he

### 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

### 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

### Authenticated Encryption: Relations among notions and analysis of the generic composition paradigm

An extended abstract of this paper appears in Tatsuaki Okamoto, editor, Advances in Cryptology ASIACRYPT 2000, Volume 1976 of Lecture Notes in Computer Science, pages 531 545, Kyoto, Japan, December 3

### 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

### 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

### 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

### 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:

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

### Outline. CSc 466/566. Computer Security. 8 : Cryptography Digital Signatures. Digital Signatures. Digital Signatures... Christian Collberg

Outline CSc 466/566 Computer Security 8 : Cryptography Digital Signatures Version: 2012/02/27 16:07:05 Department of Computer Science University of Arizona collberg@gmail.com Copyright c 2012 Christian

### 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

### 1 Construction of CCA-secure encryption

CSCI 5440: Cryptography Lecture 5 The Chinese University of Hong Kong 10 October 2012 1 Construction of -secure encryption We now show how the MAC can be applied to obtain a -secure encryption scheme.

### Lecture 13: Message Authentication Codes

Lecture 13: Message Authentication Codes Last modified 2015/02/02 In CCA security, the distinguisher can ask the library to decrypt arbitrary ciphertexts of its choosing. Now in addition to the ciphertexts

### 1 Message Authentication

Theoretical Foundations of Cryptography Lecture Georgia Tech, Spring 200 Message Authentication Message Authentication Instructor: Chris Peikert Scribe: Daniel Dadush We start with some simple questions

### 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

### 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

### 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

### 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

### 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

### Ciphertext verification security of symmetric encryption schemes

www.scichina.com info.scichina.com www.springerlink.com Ciphertext verification security of symmetric encryption schemes HU ZhenYu 1, SUN FuChun 1 & JIANG JianChun 2 1 National Laboratory of Information

### 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

### Reconsidering Generic Composition

Reconsidering Generic Composition Chanathip Namprempre Thammasat University, Thailand Phillip Rogaway University of California, Davis, USA Tom Shrimpton Portland State University, USA 1/24 What is the

### 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

### Security Protocols/Standards

Security Protocols/Standards Security Protocols/Standards Security Protocols/Standards How do we actually communicate securely across a hostile network? Provide integrity, confidentiality, authenticity

### 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

### An Introduction to Cryptography as Applied to the Smart Grid

An Introduction to Cryptography as Applied to the Smart Grid Jacques Benoit, Cooper Power Systems Western Power Delivery Automation Conference Spokane, Washington March 2011 Agenda > Introduction > Symmetric

### 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

### Digital Signatures. What are Signature Schemes?

Digital Signatures Debdeep Mukhopadhyay IIT Kharagpur What are Signature Schemes? Provides message integrity in the public key setting Counter-parts of the message authentication schemes in the public

### Digital Signatures. Murat Kantarcioglu. Based on Prof. Li s Slides. Digital Signatures: The Problem

Digital Signatures Murat Kantarcioglu Based on Prof. Li s Slides Digital Signatures: The Problem Consider the real-life example where a person pays by credit card and signs a bill; the seller verifies

### Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths

NIST Special Publication 800-131A Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths Elaine Barker and Allen Roginsky Computer Security Division Information

### Final Exam. IT 4823 Information Security Administration. Rescheduling Final Exams. Kerberos. Idea. Ticket

IT 4823 Information Security Administration Public Key Encryption Revisited April 5 Notice: This session is being recorded. Lecture slides prepared by Dr Lawrie Brown for Computer Security: Principles

### 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

### 1 Domain Extension for MACs

CS 127/CSCI E-127: Introduction to Cryptography Prof. Salil Vadhan Fall 2013 Reading. Lecture Notes 17: MAC Domain Extension & Digital Signatures Katz-Lindell Ÿ4.34.4 (2nd ed) and Ÿ12.0-12.3 (1st ed).

### Digital Signatures. Prof. Zeph Grunschlag

Digital Signatures Prof. Zeph Grunschlag (Public Key) Digital Signatures PROBLEM: Alice would like to prove to Bob, Carla, David,... that has really sent them a claimed message. E GOAL: Alice signs each

### 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

### 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

### 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

### Data integrity and data origin authentication

Network Security Elements of Applied Cryptography Hash functions and data integrity Manipulation Detection Code (MDC) Message Authentication Code (MAC) Data integrity and origin authentication Data integrity

### 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

### Remotely Keyed Encryption Using Non-Encrypting Smart Cards

THE ADVANCED COMPUTING SYSTEMS ASSOCIATION The following paper was originally published in the USENIX Workshop on Smartcard Technology Chicago, Illinois, USA, May 10 11, 1999 Remotely Keyed Encryption

### Computer Security: Principles and Practice

Computer Security: Principles and Practice Chapter 20 Public-Key Cryptography and Message Authentication First Edition by William Stallings and Lawrie Brown Lecture slides by Lawrie Brown Public-Key Cryptography

### 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

### CS558. Network Security. Boston University, Computer Science. Midterm Spring 2014.

CS558. Network Security. Boston University, Computer Science. Midterm Spring 2014. Instructor: Sharon Goldberg March 25, 2014. 9:30-10:50 AM. One-sided handwritten aid sheet allowed. No cell phone or calculators

### 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

### Authenticated Encryption (AE) Instructor: Ahmad Boorghany

Sharif University of Technology Department of Computer Engineering Data and Network Security Lab Authenticated Encryption (AE) Instructor: Ahmad Boorghany Most of the slides are obtained from Bellare and

### Digital Signatures. (Note that authentication of sender is also achieved by MACs.) Scan your handwritten signature and append it to the document?

Cryptography Digital Signatures Professor: Marius Zimand Digital signatures are meant to realize authentication of the sender nonrepudiation (Note that authentication of sender is also achieved by MACs.)

### MESSAGE AUTHENTICATION IN AN IDENTITY-BASED ENCRYPTION SCHEME: 1-KEY-ENCRYPT-THEN-MAC

MESSAGE AUTHENTICATION IN AN IDENTITY-BASED ENCRYPTION SCHEME: 1-KEY-ENCRYPT-THEN-MAC by Brittanney Jaclyn Amento A Thesis Submitted to the Faculty of The Charles E. Schmidt College of Science in Partial

### 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 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

### 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

### 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,

### 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

### SYMMETRIC ENCRYPTION. Mihir Bellare UCSD 1

SYMMETRIC ENCRYPTION Mihir Bellare UCSD 1 Syntax A symmetric encryption scheme SE = (K,E,D) consists of three algorithms: K and E may be randomized, but D must be deterministic. Mihir Bellare UCSD 2 Correct

### 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

### 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

### Introduction. Digital Signature

Introduction Electronic transactions and activities taken place over Internet need to be protected against all kinds of interference, accidental or malicious. The general task of the information technology

### 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

### Advanced Topics in Cryptography and Network Security

Advanced Topics in Cryptography and Network Security Breno de Medeiros Department of Computer Science Florida State University Advanced Topics in Cryptography and Network Security p.1 Class Reference Sheet

### Developing and Investigation of a New Technique Combining Message Authentication and Encryption

Developing and Investigation of a New Technique Combining Message Authentication and Encryption Eyas El-Qawasmeh and Saleem Masadeh Computer Science Dept. Jordan University for Science and Technology P.O.

### 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

### 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,

### Network Security. Security Attacks. Normal flow: Interruption: 孫 宏 民 hmsun@cs.nthu.edu.tw Phone: 03-5742968 國 立 清 華 大 學 資 訊 工 程 系 資 訊 安 全 實 驗 室

Network Security 孫 宏 民 hmsun@cs.nthu.edu.tw Phone: 03-5742968 國 立 清 華 大 學 資 訊 工 程 系 資 訊 安 全 實 驗 室 Security Attacks Normal flow: sender receiver Interruption: Information source Information destination

### CPSC 467b: Cryptography and Computer Security

CPSC 467b: Cryptography and Computer Security Michael J. Fischer Lecture 1 January 9, 2012 CPSC 467b, Lecture 1 1/22 Course Overview Symmetric Cryptography CPSC 467b, Lecture 1 2/22 Course Overview CPSC

### 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

### Applying Symmetric Encryption

Applying Symmetric Encryption Technical Report Falko Strenzke cryptosource GmbH, Darmstadt fstrenzke@cryptosource.de www.cryptosource.de February 13, 2015 This work, which is intended to close a gap left

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...

### 1 Signatures vs. MACs

CS 120/ E-177: Introduction to Cryptography Salil Vadhan and Alon Rosen Nov. 22, 2006 Lecture Notes 17: Digital Signatures Recommended Reading. Katz-Lindell 10 1 Signatures vs. MACs Digital signatures

### CSC474/574 - Information Systems Security: Homework1 Solutions Sketch

CSC474/574 - Information Systems Security: Homework1 Solutions Sketch February 20, 2005 1. Consider slide 12 in the handout for topic 2.2. Prove that the decryption process of a one-round Feistel cipher

### CS 393 Network Security. Nasir Memon Polytechnic University Module 11 Secure Email

CS 393 Network Security Nasir Memon Polytechnic University Module 11 Secure Email Course Logistics HW 5 due Thursday Graded exams returned and discussed. Read Chapter 5 of text 4/2/02 Module 11 - Secure

### Network Security. Abusayeed Saifullah. CS 5600 Computer Networks. These slides are adapted from Kurose and Ross 8-1

Network Security Abusayeed Saifullah CS 5600 Computer Networks These slides are adapted from Kurose and Ross 8-1 Public Key Cryptography symmetric key crypto v requires sender, receiver know shared secret

### Cryptography and Network Security Chapter 11. Fourth Edition by William Stallings

Cryptography and Network Security Chapter 11 Fourth Edition by William Stallings Chapter 11 Message Authentication and Hash Functions At cats' green on the Sunday he took the message from the inside of

### Digital signatures. Informal properties

Digital signatures Informal properties Definition. A digital signature is a number dependent on some secret known only to the signer and, additionally, on the content of the message being signed Property.

### 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

### Computer Security CS 426. CS426 Fall 2010/Lecture 40 1

Computer Security CS 426 Review for Final Exam CS426 Fall 2010/Lecture 40 1 Basic Concepts Confidentiality Integrity Availability Authenticity Integrity (in communications) Non-repudiation Privacy (general

### 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

### Cryptography and Key Management Basics

Cryptography and Key Management Basics Erik Zenner Technical University Denmark (DTU) Institute for Mathematics e.zenner@mat.dtu.dk DTU, Oct. 23, 2007 Erik Zenner (DTU-MAT) Cryptography and Key Management

### Recommendation for Applications Using Approved Hash Algorithms

NIST Special Publication 800-107 Revision 1 Recommendation for Applications Using Approved Hash Algorithms Quynh Dang Computer Security Division Information Technology Laboratory C O M P U T E R S E C

### 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

### Announcement. Final exam: Wed, June 9, 9:30-11:18 Scope: materials after RSA (but you need to know RSA) Open books, open notes. Calculators allowed.

Announcement Final exam: Wed, June 9, 9:30-11:18 Scope: materials after RSA (but you need to know RSA) Open books, open notes. Calculators allowed. 1 We have learned Symmetric encryption: DES, 3DES, AES,

### Lecture 5 - Cryptography

CSE497b Introduction to Computer and Network Security - Spring 2007 - Professors Jaeger Lecture 5 - Cryptography CSE497b - Spring 2007 Introduction Computer and Network Security Professor Jaeger www.cse.psu.edu/~tjaeger/cse497b-s07/

### Message Authentication Codes 133

Message Authentication Codes 133 CLAIM 4.8 Pr[Mac-forge A,Π (n) = 1 NewBlock] is negligible. We construct a probabilistic polynomial-time adversary A who attacks the fixed-length MAC Π and succeeds in

### 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

### 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)

### Recommendation for Applications Using Approved Hash Algorithms

NIST Special Publication 800-107 Recommendation for Applications Using Approved Hash Algorithms Quynh Dang Computer Security Division Information Technology Laboratory C O M P U T E R S E C U R I T Y February