# Cryptography and Network Security

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 Cryptography and Network Security Spring Lecture 3: Block ciphers and DES Ion Petre Department of IT, Åbo Akademi University January 17,

2 Data Encryption Standard We focus now on the most widely used symmetric cipher: DES DES has been replaced by AES as a standard We will use DES to illustrate the principles of modern symmetric ciphers Adopted in 1977 by the National Bureau of Standards (US), nowadays NIST Originates from an IBM project from late 1960s led by Feistel Project ended in 1971 with the development of LUCIFER (key 128 bits) LUCIFER was then refined with the help of NSA to produce DES (key 56 bits) Immediate criticism: the reduction in key length was enormous and the internal details of the design were (and remained) classified information 1994: DES is reaffirmed as a standard for 5 more years 1999: DES should only be used for legacy systems and 3DES should replace it January 17,

3 Block cipher principles Stream cipher is one that encrypts a digital data stream one bit (or byte) at a time Example: autokey Vigenère system Block cipher is one in which the plaintext is divided in blocks and one block is encrypted at one time producing a ciphertext of equal length Similar to substitution ciphers on very big characters: 64 bits or 128 bits are typical block lengths Many modern ciphers are block ciphers January 17,

4 Principle: Substitution-Permutation Ciphers Claude Shannon (1949) introduced idea of substitution-permutation (S-P) networks These form the basis for modern substitution-transposition product cipher S-P networks are based on the two primitive cryptographic operations we have seen before: substitution (S-box) permutation (P-box) The goal is to provide confusion and diffusion of message January 17,

5 Confusion and Diffusion Cipher need to completely obscure statistical properties of original message A one-time pad does this More practically Shannon (1949) suggested to combine elements to obtain: Diffusion dissipates statistical structure of plaintext over bulk of ciphertext Makes the statistical relationship plaintext - ciphertext as complex as possible Achieved by requiring that every digit of the plaintext affects many digits of the ciphertext (equivalently, every digit of the ciphertext is affected by many digits of the plaintext) Confusion makes relationship between ciphertext and key as complex as possible Makes it difficult to discover the key starting from the ciphertext The principles of confusion and diffusion are the most essential concepts in the design of modern block ciphers they defend against statistical attacks January 17,

6 Feistel Cipher Structure Most modern block encryption algorithms use the Feistel structure Horst Feistel was the leader of the IBM team that worked in late 1960s on LUCIFER He devised the so-called feistel cipher Algorithm structure perform n rounds, each round has the following structure (for encryption and decryption): Input is of length 2w (bits), key is K Divide the input into two halves L 0 and R 0 L 1 = R 0, R 1 =L 0 f(r 0,K) In the next round use (L 1, R 1 ) instead of (L 0, R 0 ), etc. Function f is the same in all rounds but uses a different subkey in each round the subkey of each round is generated from the key January 17,

7 Feistel Cipher Structure January 17,

8 Feistel Cipher Design Principles block size increasing size improves security, but slows cipher key size increasing size improves security, makes exhaustive key searching harder, but may slow cipher number of rounds increasing number improves security, but slows cipher subkey generation greater complexity can make analysis harder, but slows cipher round function greater complexity can make analysis harder, but slows cipher fast software en/decryption & ease of analysis are more recent concerns for practical use and testing January 17,

9 Feistel Cipher Decryption vs Encryption: the same algorithm (with keys in reverse order) January 17,

10 Feistel decryption Decryption is the same as encryption and does not require any property for function f (not even to be invertible) LD/RD left/right half in the decryption algorithm LE/RE left/right half in the encryption algorithm denotes XOR: 0 0=0, 1 1=0, 0 1= 1 0=1 Encryption Input: the plaintext (LE 0, RE 0 ) Round i (1 to 16) performs on input (LE i-1, RE i-1 ) the operations: LE i =RE i-1, RE i =LE i-1 f(re i-1,k i ) This is the input to next round The key of round i is K i, Output: the ciphertext (RE 16, LE 16 ) Decryption Input: The ciphertext (LD 0, RD 0 )= (RE 16, LE 16 ) Round i (1 to 16) performs on input (LD i-1, RD i-1 ) the operations: LD i =RD i-1, RD i =LD i-1 f(rd i-1,k 16-i ) This is the input to next round The key of round i is K 16-i, This algorithm is CORRECT after round i we have LD i =RE 16-i, RD i =LE 16-i : PROOF: Input to the first round: LD 0 =RE 16, RD 0 =LE 16 Induction: assume it holds for i-1, prove it for i LD i-1 =RE 16-i+1, RD i-1 =LE 16-i+1 Then: LD i =RD i-1 =LE 16-i+1 =RE 16-i RD i =LD i-1 f(rd i-1, K 16-i )=RE 16-i+1 f(le 16-i+1, K 16-i )= =(LE 16-i f(re 16-i,K 16-i+1 )) f(re 16-i,K 16-i )=LE 16-i Result: (RE 16-i, LE 16-i ) Output: the plaintext (RD 16, LD 16 )=(LE 0, RE 0 ) January 17,

11 DES DES encryption/decryption Strength of DES Design principles Cryptanalysis January 17,

12 DES encryption scheme The plaintext (64 bits) passes through an initial permutation IP (on 64 bits) Then follow 16 identical rounds in each round a different subkey is used; each subkey is generated from the key After round 16, swap the left half with the right half Apply the inverse of the initial permutation IP -1 (on 64 bits) January 17,

13 DES encryption scheme January 17,

14 Initial permutation and its inverse January 17,

15 Details of a single round of DES Consider L the left half of the input to the round and R its right half each of them have 32 bits As in any Feistel cipher the overall processing is L i =R i-1, R i =L i-1 F(R i-1,k i ) The round subkey K i has 48 bits (details later on how it is generated) R is expanded from 32 to 48 bits using an expansion permutation E this is a table that defines a permutation, duplicating in the same time 16 of the bits in R These 48 bits are XORED with the subkey K i The 48-bit result passes through a substitution function that produces a 32- bit output Apply then a permutation P January 17,

16 A single round of DES January 17,

17 The scheme of the function F(R,K) in DES January 17,

18 Details of a single round of DES January 17,

19 The substitutions in the DES rounds: S-boxes There are 8 S-boxes, each of them accepting a 6-bit input and producing 4-bit output The S-boxes are 4 x 16 tables (shown on the next slide) and are used as follows: The first and the last bit of the input to the S-box form a 2-bit binary number that selects the row of the S-box (rows are from 0 to 3) The middle four bits select the column of the S-box (columns are from 0 to 15) The decimal value in the selected entry of the S-box is converted to its 4-bit binary representation to produce the output January 17,

20 Definition of S-boxes Example: consider the input to S-box S 1 The row is : 01 (i.e. 1) The column is : 1100 (i.e. 12) The value in the selected cell is 9 Output is 1001 Note that each row of each S-box is in fact an invertible substitution on 4 bits (permutation of numbers from 0 to 15) Note also that the output of the S-box is immediately permuted in DES so that it spreads in the ciphertext January 17,

21 Subkey generation In the general scheme of DES is shown that a 64-bit key is used the bits of the key are numbered from 1 to 64. The algorithm ignores every 8 th bit thus, the key for DES is effectively 56-bit long Before round 1 of DES, they key is permuted according to a table labeled Permuted Choice One (see next slide) the resulting 56-bit key is split into its two 28-bit halves labeled C 0 and D 0 In each round, Ci-1 and Di-1 are separately subjected to a circular left shift of one or two bits according to the table on the next slide the shifted values will be input to next round The shifted values serve as input to Permuted Choice Two (see next slide) which produces a 48-bit output: the subkey of the current round January 17,

22 Subkey generation In the general scheme of DES is shown that a 64-bit key is used the bits of the key are numbered from 1 to 64. The algorithm ignores every 8 th bit thus, the key for DES is effectively 56-bit long Before round 1 of DES, they key is permuted according to a table labeled Permuted Choice One the resulting 56-bit key is split into its two 28-bit halves labeled C 0 and D 0 In each round, Ci-1 and Di-1 are separately subjected to a circular left shift of one or two bits according to the table on the next slide the shifted values will be input to next round The shifted values serve as input to Permuted Choice Two which produces a 48-bit output: the subkey of the current round January 17,

23 DES decryption Like in any Feistel cipher, decryption works just like encryption with the subkeys used in reverse order January 17,

24 Analysis of DES Avalanche effect: this is a desirable property of any encryption algorithm A small change (even 1 bit) in the plaintext should produce significant change in the ciphertext Example: consider two blocks of 64 zeros and in the second block rewrite 1 on the first position. Encrypt them both with DES: depending on the key, the result may have 34 different bits! A small change (even 1 bit) in the key should produce significant change in the ciphertext Example: a change of one bit in the DES key may produce 35 different bits in the encryption of the same plaintext January 17,

25 Strength of DES Two main concerns with DES: the length of the key and the nature of the algorithm The key is rather short: 56 bits there are 2 56 possible keys, around 7.2 x In average, only half of the keys have to be tried to break the system In principle it should take long time to break the system Things are quicker with dedicated hardware: 1998 a special machine was built for less than \$ breaking DES in less than 3 days, 2006 estimates are that a hardware costing around \$ may break DES within a day DES has no export restrictions from NSA! 40-bit RC4 key is also insecure 128-but keys seem to be secure Important difficulty in breaking any system: unless the plaintext is known, we have to recognize when we have broken the system: we have to recognize the plaintext when we find it This is not trivial if the file is binary, compressed, etc. Automated procedures to do that are needed (and indeed some exist) January 17,

26 Strength of DES Nature of the algorithm There has always been a concern about the design of DES, especially about the design of S-boxes perhaps they have been designed in such a way as to ensure a trapdoor to the algorithm break it without having to search for the key The design criteria for the S-boxes (and for the rest of the algorithm) have been classified information and NSA was involved in the design Many regularities and unexpected behavior of the S-boxes have been reported On the other hand, changing the S-boxes slightly seems to weaken the algorithm No fatal weaknesses in the S-boxes have been (publicly) reported so far January 17,

27 Cryptanalysis of DES There are ways to break DES significantly quicker than with the brute-force attack: differential and linear cryptanalysis Differential cryptanalysis Published in the open literature after 1990: Murphy and then Biham and Shamir (published a book on this) Idea: Knowing the XOR of the message halves before and after a round, one may try to deduce the subkey used in that round DES can be broken in 2 47 steps, requiring 2 47 chosen plaintexts The need for so many chosen plaintexts makes its applicability limited This attack seems to have been known to the DES design team and NSA 20 years before it was published in the open literature! Linear cryptanalysis More recent attack (Matsui, 1993): find linear approximations to describe the transformations in DES Can find the DES key given 2 47 known plaintexts Still impractical method January 17,

28 DES cryptanalysis chronology (Wikipedia) July June 1997 Biham and Shamir rediscover differential cryptanalysis, and apply it to a 15-round DESlike cryptosystem. Biham and Shamir report the first theoretical attack with less complexity than brute force: differential cryptanalysis. However, it requires an unrealistic 2 47 chosen plaintexts. The first experimental cryptanalysis of DES is performed using linear cryptanalysis (Matsui, 1994). The DESCHALL Project breaks a message encrypted with DES for the first time in public. July 1998 The EFF's DES cracker (Deep Crack) breaks a DES key in 56 hours. January 1999 Together, Deep Crack and distributed.net break a DES key in 22 hours and 15 minutes. November 2001 The Advanced Encryption Standard is published in FIPS 197 May 2002 The AES standard becomes effective May 2005 NIST withdraws FIPS 46-3 (see Federal Register vol 70, number 96) April 2006 November 2008 The FPGA based parallel machine COPACOBANA of the Universities of Bochum and Kiel, Germany, breaks DES in 9 days at \$10,000 hardware cost. Within a year software improvements reduced the average time to 6.4 days. The successor of COPACOBANA, the RIVYERA machine reduced the average time to less than one single day. 28

### Cryptography and Network Security Chapter 3

Cryptography and Network Security Chapter 3 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 3 Block Ciphers and the Data Encryption Standard All the afternoon

### The Data Encryption Standard (DES)

The Data Encryption Standard (DES) As mentioned earlier there are two main types of cryptography in use today - symmetric or secret key cryptography and asymmetric or public key cryptography. Symmetric

### Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur

Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Lecture No. # 11 Block Cipher Standards (DES) (Refer Slide

### CSCE 465 Computer & Network Security

CSCE 465 Computer & Network Security Instructor: Dr. Guofei Gu http://courses.cse.tamu.edu/guofei/csce465/ Secret Key Cryptography (I) 1 Introductory Remarks Roadmap Feistel Cipher DES AES Introduction

### Cryptography and Network Security Block Cipher

Cryptography and Network Security Block Cipher Xiang-Yang Li Modern Private Key Ciphers Stream ciphers The most famous: Vernam cipher Invented by Vernam, ( AT&T, in 1917) Process the message bit by bit

### Shift Cipher. Ahmet Burak Can Hacettepe University. Substitution Cipher. Enigma Machine. How perfect secrecy can be satisfied?

One Time Pad, Block Ciphers, Encryption Modes Ahmet Burak Can Hacettepe University abc@hacettepe.edu.tr Basic Ciphers Shift Cipher Brute-force attack can easily break Substitution Cipher Frequency analysis

### Lecture 4 Data Encryption Standard (DES)

Lecture 4 Data Encryption Standard (DES) 1 Block Ciphers Map n-bit plaintext blocks to n-bit ciphertext blocks (n = block length). For n-bit plaintext and ciphertext blocks and a fixed key, the encryption

### 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/

### 6 Block Ciphers. 6.1 Block Ciphers CA642: CRYPTOGRAPHY AND NUMBER THEORY 1

CA642: CRYPTOGRAPHY AND NUMBER THEORY 1 6 Block Ciphers 6.1 Block Ciphers Block Ciphers Plaintext is divided into blocks of fixed length and every block is encrypted one at a time. A block cipher is a

### Lezione 6. DES (Data Encryption Standard) 6.1

Lezione 6 DES (Data Encryption Standard) 6.1 6.2 6-1 INTRODUCTION The Data Encryption Standard (DES) is a symmetric- key block cipher published by the National Institute of Standards and Technology (NIST).

### Block encryption. CS-4920: Lecture 7 Secret key cryptography. Determining the plaintext ciphertext mapping. CS4920-Lecture 7 4/1/2015

CS-4920: Lecture 7 Secret key cryptography Reading Chapter 3 (pp. 59-75, 92-93) Today s Outcomes Discuss block and key length issues related to secret key cryptography Define several terms related to secret

### 1 Data Encryption Algorithm

Date: Monday, September 23, 2002 Prof.: Dr Jean-Yves Chouinard Design of Secure Computer Systems CSI4138/CEG4394 Notes on the Data Encryption Standard (DES) The Data Encryption Standard (DES) has been

### Network Security. Chapter 3 Symmetric Cryptography. Symmetric Encryption. Modes of Encryption. Symmetric Block Ciphers - Modes of Encryption ECB (1)

Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle Network Security Chapter 3 Symmetric Cryptography General Description Modes of ion Data ion Standard (DES)

### Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur

Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Module No. #01 Lecture No. #10 Symmetric Key Ciphers (Refer

### Symmetric Key cryptosystem

SFWR C03: Computer Networks and Computer Security Mar 8-11 200 Lecturer: Kartik Krishnan Lectures 22-2 Symmetric Key cryptosystem Symmetric encryption, also referred to as conventional encryption or single

### 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

### Lecture 3: Block Ciphers and the Data Encryption Standard. Lecture Notes on Computer and Network Security. by Avi Kak (kak@purdue.

Lecture 3: Block Ciphers and the Data Encryption Standard Lecture Notes on Computer and Network Security by Avi Kak (kak@purdue.edu) January 15, 2016 12:28am c 2016 Avinash Kak, Purdue University Goals:

### Keywords Web Service, security, DES, cryptography.

Volume 3, Issue 10, October 2013 ISSN: 2277 128X International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com Provide the

### 6 Data Encryption Standard (DES)

6 Data Encryption Standard (DES) Objectives In this chapter, we discuss the Data Encryption Standard (DES), the modern symmetric-key block cipher. The following are our main objectives for this chapter:

### Applied Cryptology. Ed Crowley

Applied Cryptology Ed Crowley 1 Basics Topics Basic Services and Operations Symmetric Cryptography Encryption and Symmetric Algorithms Asymmetric Cryptography Authentication, Nonrepudiation, and Asymmetric

### The Advanced Encryption Standard: Four Years On

The Advanced Encryption Standard: Four Years On Matt Robshaw Reader in Information Security Information Security Group Royal Holloway University of London September 21, 2004 The State of the AES 1 The

6.857 Computer and Network Security Fall Term, 1997 Lecture 4 : 16 September 1997 Lecturer: Ron Rivest Scribe: Michelle Goldberg 1 Conditionally Secure Cryptography Conditionally (or computationally) secure

### Cryptography and Network Security. Prof. D. Mukhopadhyay. Department of Computer Science and Engineering. Indian Institute of Technology, Kharagpur

Cryptography and Network Security Prof. D. Mukhopadhyay Department of Computer Science and Engineering Indian Institute of Technology, Kharagpur Module No. # 01 Lecture No. # 12 Block Cipher Standards

### Enhancing Advanced Encryption Standard S-Box Generation Based on Round Key

Enhancing Advanced Encryption Standard S-Box Generation Based on Round Key Julia Juremi Ramlan Mahmod Salasiah Sulaiman Jazrin Ramli Faculty of Computer Science and Information Technology, Universiti Putra

### Security usually depends on the secrecy of the key, not the secrecy of the algorithm (i.e., the open design model!)

1 A cryptosystem has (at least) five ingredients: 1. 2. 3. 4. 5. Plaintext Secret Key Ciphertext Encryption algorithm Decryption algorithm Security usually depends on the secrecy of the key, not the secrecy

### Lecture Note 8 ATTACKS ON CRYPTOSYSTEMS I. Sourav Mukhopadhyay

Lecture Note 8 ATTACKS ON CRYPTOSYSTEMS I Sourav Mukhopadhyay Cryptography and Network Security - MA61027 Attacks on Cryptosystems Up to this point, we have mainly seen how ciphers are implemented. We

### uses same key for encryption, decryption classical, conventional, single-key encryption

CEN 448 Security and Internet Protocols Chapter 2 Classical Encryption Techniques Dr. Mostafa Hassan Dahshan Computer Engineering Department College of Computer and Information Sciences King Saud University

### Split Based Encryption in Secure File Transfer

Split Based Encryption in Secure File Transfer Parul Rathor, Rohit Sehgal Assistant Professor, Dept. of CSE, IET, Nagpur University, India Assistant Professor, Dept. of CSE, IET, Alwar, Rajasthan Technical

### The Advanced Encryption Standard (AES)

The Advanced Encryption Standard (AES) All of the cryptographic algorithms we have looked at so far have some problem. The earlier ciphers can be broken with ease on modern computation systems. The DES

### Secret File Sharing Techniques using AES algorithm. C. Navya Latha 200201066 Garima Agarwal 200305032 Anila Kumar GVN 200305002

Secret File Sharing Techniques using AES algorithm C. Navya Latha 200201066 Garima Agarwal 200305032 Anila Kumar GVN 200305002 1. Feature Overview The Advanced Encryption Standard (AES) feature adds support

### Computer Science A Cryptography and Data Security. Claude Crépeau

Computer Science 308-547A Cryptography and Data Security Claude Crépeau These notes are, largely, transcriptions by Anton Stiglic of class notes from the former course Cryptography and Data Security (308-647A)

### A PPENDIX H RITERIA FOR AES E VALUATION C RITERIA FOR

A PPENDIX H RITERIA FOR AES E VALUATION C RITERIA FOR William Stallings Copyright 20010 H.1 THE ORIGINS OF AES...2 H.2 AES EVALUATION...3 Supplement to Cryptography and Network Security, Fifth Edition

### Network Security. Security. Security Services. Crytographic algorithms. privacy authenticity Message integrity. Public key (RSA) Message digest (MD5)

Network Security Security Crytographic algorithms Security Services Secret key (DES) Public key (RSA) Message digest (MD5) privacy authenticity Message integrity Secret Key Encryption Plain text Plain

### A Comparative Study Of Two Symmetric Encryption Algorithms Across Different Platforms.

A Comparative Study Of Two Symmetric Algorithms Across Different Platforms. Dr. S.A.M Rizvi 1,Dr. Syed Zeeshan Hussain 2 and Neeta Wadhwa 3 Deptt. of Computer Science, Jamia Millia Islamia, New Delhi,

### Symmetric and asymmetric cryptography overview

Symmetric and asymmetric cryptography overview Modern cryptographic methods use a key to control encryption and decryption Two classes of key-based encryption algorithms symmetric (secret-key) asymmetric

### Network Security. Omer Rana

Network Security Omer Rana CM0255 Material from: Cryptography Components Sender Receiver Plaintext Encryption Ciphertext Decryption Plaintext Encryption algorithm: Plaintext Ciphertext Cipher: encryption

### A PPENDIX G S IMPLIFIED DES

A PPENDIX G S IMPLIFIED DES William Stallings opyright 2010 G.1 OVERVIEW...2! G.2 S-DES KEY GENERATION...3! G.3 S-DES ENRYPTION...4! Initial and Final Permutations...4! The Function f K...5! The Switch

### CRYPTOGRAPHIC ALGORITHMS (AES, RSA)

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA CRYPTOGRAPHIC ALGORITHMS (AES, RSA) A PAPER SUBMITTED TO PROFESSOR GILBERT S. YOUNG IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE COURSE CS530 : ADVANCED

### Overview of Classification of Encryption Methods and Survey on the Different Block Ciphers

Overview of Classification of Encryption Methods and Survey on the Different Block Ciphers Smitha Dept. of CSE, SSE Srinivas school of Engineering Mangalore, Karnataka, India Prof. Kishore Baglodi Dept.

### APNIC elearning: Cryptography Basics. Contact: esec02_v1.0

APNIC elearning: Cryptography Basics Contact: training@apnic.net esec02_v1.0 Overview Cryptography Cryptographic Algorithms Encryption Symmetric-Key Algorithm Block and Stream Cipher Asymmetric Key Algorithm

ADVANCED ENCRYPTION STANDARD (AES) Tran Song Dat Phuc Department of Computer Science and Engineering Seoul National University of Science and Technology 2013-2014 Outline AES History AES Operations Advanced

### Cryptography and Cryptanalysis

Cryptography and Cryptanalysis Feryâl Alayont University of Arizona December 9, 2003 1 Cryptography: derived from the Greek words kryptos, meaning hidden, and graphos, meaning writing. Cryptography is

### 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

### Cryptography: Motivation. Data Structures and Algorithms Cryptography. Secret Writing Methods. Many areas have sensitive information, e.g.

Cryptography: Motivation Many areas have sensitive information, e.g. Data Structures and Algorithms Cryptography Goodrich & Tamassia Sections 3.1.3 & 3.1.4 Introduction Simple Methods Asymmetric methods:

### Crypto Basics. Ed Crowley. Spring 2010

Crypto Basics Ed Crowley Spring 2010 Kerckhoff s Principle Symmetric Crypto Overview Key management problem Attributes Modes Symmetric Key Algorithms DES Attributes Modes 3DES AES Other Symmetric Ciphers

### AStudyofEncryptionAlgorithmsAESDESandRSAforSecurity

Global Journal of Computer Science and Technology Network, Web & Security Volume 13 Issue 15 Version 1.0 Year 2013 Type: Double Blind Peer Reviewed International Research Journal Publisher: Global Journals

### F3 Symmetric Encryption

F3 Symmetric Encryption Cryptographic Algorithms: Overview During this course two main applications of cryptographic algorithms are of principal interest: Encryption of data: transforms plaintext data

### CRYPTOGRAPHIC PRIMITIVES AN INTRODUCTION TO THE THEORY AND PRACTICE BEHIND MODERN CRYPTOGRAPHY

CRYPTOGRAPHIC PRIMITIVES AN INTRODUCTION TO THE THEORY AND PRACTICE BEHIND MODERN CRYPTOGRAPHY Robert Sosinski Founder & Engineering Fellow Known as "America's Cryptologic Wing", is the only Air Force

### Network Security: Cryptography CS/SS G513 S.K. Sahay

Network Security: Cryptography CS/SS G513 S.K. Sahay BITS-Pilani, K.K. Birla Goa Campus, Goa S.K. Sahay Network Security: Cryptography 1 Introduction Network security: measure to protect data/information

### 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

### 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?

### The Advanced Encryption Standard (AES)

The Advanced Encryption Standard (AES) Conception - Why A New Cipher? Conception - Why A New Cipher? DES had outlived its usefulness Vulnerabilities were becoming known 56-bit key was too small Too slow

### Data Encryption A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. we would encrypt the string IDESOFMARCH as follows:

Data Encryption Encryption refers to the coding of information in order to keep it secret. Encryption is accomplished by transforming the string of characters comprising the information to produce a new

### Network Security: Secret Key Cryptography

1 Network Security: Secret Key Cryptography Henning Schulzrinne Columbia University, New York schulzrinne@cs.columbia.edu Columbia University, Fall 2000 c 1999-2000, Henning Schulzrinne Last modified September

### C Simplified DES. William Stallings Copyright 2006

APPENDIX C Simplified DES C.1 Overview...2 C.2 S-DES Key Generation...3 C.3 S-DES Encryption...3 Initial and Final Permutations...3 The Function... The Switch Function...5 C. Analysis of Simplified DES...5

### Implementation of Full -Parallelism AES Encryption and Decryption

Implementation of Full -Parallelism AES Encryption and Decryption M.Anto Merline M.E-Commuication Systems, ECE Department K.Ramakrishnan College of Engineering-Samayapuram, Trichy. Abstract-Advanced Encryption

### {(i,j) 1 < i,j < n} pairs, X and X i, such that X and X i differ. exclusive-or sums. ( ) ( i ) V = f x f x

ON THE DESIGN OF S-BOXES A. F. Webster and S. E. Tavares Department of Electrical Engineering Queen's University Kingston, Ont. Canada The ideas of completeness and the avalanche effect were first introduced

### 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 Goals v understand principles of network security: cryptography and its many uses beyond

### Secret Writing. Introduction to Cryptography. Encryption. Decryption. Kerckhoffs s ( ) Principle. Security of Cryptographic System

Introduction to Cryptography ECEN 1200, Telecommunications 1 Secret Writing Cryptography is the science and study of secret writing. More specifically, cryptography is concerned with techniques for enciphering

### 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

### A Study of New Trends in Blowfish Algorithm

A Study of New Trends in Blowfish Algorithm Gurjeevan Singh*, Ashwani Kumar**, K. S. Sandha*** *(Department of ECE, Shaheed Bhagat Singh College of Engg. & Tech. (Polywing), Ferozepur-152004) **(Department

### 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

### Improving Performance of Secure Data Transmission in Communication Networks Using Physical Implementation of AES

Improving Performance of Secure Data Transmission in Communication Networks Using Physical Implementation of AES K Anjaneyulu M.Tech Student, Y.Chalapathi Rao, M.Tech, Ph.D Associate Professor, Mr.M Basha,

### A Secure Software Implementation of Nonlinear Advanced Encryption Standard

IOSR Journal of VLSI and Signal Processing (IOSR-JVSP) ISSN: 2319 4200, ISBN No. : 2319 4197 Volume 1, Issue 5 (Jan. - Feb 2013), PP 44-48 A Secure Software Implementation of Nonlinear Advanced 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

### Today ENCRYPTION. Cryptography example. Basic principles of cryptography

Today ENCRYPTION The last class described a number of problems in ensuring your security and privacy when using a computer on-line. This lecture discusses one of the main technological solutions. The use

### 9/17/2015. Cryptography Basics. Outline. Encryption/Decryption. Cryptanalysis. Caesar Cipher. Mono-Alphabetic Ciphers

Cryptography Basics IT443 Network Security Administration Instructor: Bo Sheng Outline Basic concepts in cryptography system Secret cryptography Public cryptography Hash functions 1 2 Encryption/Decryption

### 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,

### Design and Implementation of Asymmetric Cryptography Using AES Algorithm

Design and Implementation of Asymmetric Cryptography Using AES Algorithm Madhuri B. Shinde Student, Electronics & Telecommunication Department, Matoshri College of Engineering and Research Centre, Nashik,

### 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

### Cryptography and Network Security Chapter 9

Cryptography and Network Security Chapter 9 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 9 Public Key Cryptography and RSA Every Egyptian received two names,

### 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.

### Cryptography and Network Security Department of Computer Science and Engineering Indian Institute of Technology Kharagpur

Cryptography and Network Security Department of Computer Science and Engineering Indian Institute of Technology Kharagpur Module No. # 01 Lecture No. # 05 Classic Cryptosystems (Refer Slide Time: 00:42)

### 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

### Effective Secure Encryption Scheme [One Time Pad] Using Complement Approach Sharad Patil 1 Ajay Kumar 2

Effective Secure Encryption Scheme [One Time Pad] Using Complement Approach Sharad Patil 1 Ajay Kumar 2 Research Student, Bharti Vidyapeeth, Pune, India sd_patil057@rediffmail.com Modern College of Engineering,

Dierential Cryptanalysis of DES-like Cryptosystems Eli Biham Adi Shamir The Weizmann Institute of Science Department of Apllied Mathematics July 19, 1990 Abstract The Data Encryption Standard (DES) is

### Stream Ciphers. Example of Stream Decryption. Example of Stream Encryption. Real Cipher Streams. Terminology. Introduction to Modern Cryptography

Introduction to Modern Cryptography Lecture 2 Symmetric Encryption: Stream & Block Ciphers Stream Ciphers Start with a secret key ( seed ) Generate a keying stream i-th bit/byte of keying stream is a function

### 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

### Introduction. Where Is The Threat? Encryption Methods for Protecting Data. BOSaNOVA, Inc. Phone: 866-865-5250 Email: info@theq3.com Web: www.theq3.

Introduction Within the last ten years, there has been a vast increase in the accumulation and communication of digital computer data in both the private and public sectors. Much of this information has

### CS 392/681 Computer Security. Module 1 Private Key Cryptography

CS 392/681 Computer Security Module 1 Private Key Cryptography Logistics Office hours - Thursday 5 to 6 (tentative). Welcome to walk in anytime. Emails until midnight. AIM: evilproffy. Lab 0 due date postponed

### FPGA BASED HARDWARE KEY FOR TEMPORAL ENCRYPTION

FPGA BASED HARDWARE KEY FOR TEMPORAL ENCRYPTION Abstract In this paper, a novel encryption scheme with time based key technique on an FPGA is presented. Time based key technique ensures right key to be

### The Elements of Cryptography

The Elements of Cryptography (March 30, 2016) Abdou Illia Spring 2016 Learning Objectives Discuss Cryptography Terminology Discuss Symmetric Key Encryption Discuss Asymmetric Key Encryption Distinguish

### Cryptography and Network Security Chapter 6

Cryptography and Network Security Chapter 6 Fifth Edition by William Stallings Lecture slides by Lawrie Brown (with edits by RHB) Chapter 6 Block Cipher Operation Many savages at the present day regard

### ARCHIVED PUBLICATION

ARCHIVED PUBLICATION The attached publication, FIPS Publication 46-3 (reaffirmed October 25, 1999), was withdrawn on May 19, 2005 and is provided here only for historical purposes. For related information,

### SeChat: An AES Encrypted Chat

Name: Luis Miguel Cortés Peña GTID: 901 67 6476 GTG: gtg683t SeChat: An AES Encrypted Chat Abstract With the advancement in computer technology, it is now possible to break DES 56 bit key in a meaningful

### 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

### Network Security. Chapter 2 Basics 2.1 Symmetric Cryptography. Cryptographic algorithms: outline. Basic Terms: Block cipher and Stream cipher

Chair for Network Architectures and Services Department of Informatics TU München Prof. Carle Cryptographic algorithms: outline Network Security Cryptographic Algorithms Chapter 2 Basics 2.1 Symmetric

### Chapter 10 Asymmetric-Key Cryptography

Chapter 10 Asymmetric-Key Cryptography Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10.1 Chapter 10 Objectives Present asymmetric-key cryptography. Distinguish

### A Comparison of the 3DES and AES Encryption Standards

, pp.241-246 http://dx.doi.org/10.14257/ijsia.2015.9.7.21 A Comparison of the 3DES and AES Encryption Standards Noura Aleisa n.aleisa@seu.edu.sa Abstract A comparison of two encryption standards, 3DES

### 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

### A New Digital Encryption Scheme: Binary Matrix Rotations Encryption Algorithm

International Journal of Research Studies in Computer Science and Engineering (IJRSCSE) Volume 2, Issue 2, February 2015, PP 18-27 ISSN 2349-4840 (Print) & ISSN 2349-4859 (Online) www.arcjournals.org A

### Cyber Security Workshop Encryption Reference Manual

Cyber Security Workshop Encryption Reference Manual May 2015 Basic Concepts in Encoding and Encryption Binary Encoding Examples Encryption Cipher Examples 1 P a g e Encoding Concepts Binary Encoding Basics

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...

### 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:

### Lecture 8: AES: The Advanced Encryption Standard. Lecture Notes on Computer and Network Security. by Avi Kak (kak@purdue.edu)

Lecture 8: AES: The Advanced Encryption Standard Lecture Notes on Computer and Network Security by Avi Kak (kak@purdue.edu) May 1, 2015 12:14 Noon c 2015 Avinash Kak, Purdue University Goals: To review

### 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

### CLOUD COMPUTING SECURITY ARCHITECTURE - IMPLEMENTING DES ALGORITHM IN CLOUD FOR DATA SECURITY

CLOUD COMPUTING SECURITY ARCHITECTURE - IMPLEMENTING DES ALGORITHM IN CLOUD FOR DATA SECURITY Varun Gandhi 1 Department of Computer Science and Engineering, Dronacharya College of Engineering, Khentawas,

### A NEW DNA BASED APPROACH OF GENERATING KEY-DEPENDENT SHIFTROWS TRANSFORMATION

A NEW DNA BASED APPROACH OF GENERATING KEY-DEPENDENT SHIFTROWS TRANSFORMATION Auday H. Al-Wattar 1, Ramlan Mahmod 2, Zuriati Ahmad Zukarnain3, and Nur Izura Udzir4, 1 Faculty of Computer Science and Information