We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byJada Richards
Modified over 3 years ago
Symmetric Encryption Prof. Ravi Sandhu
2 © Ravi Sandhu SECRET KEY CRYPTOSYSTEM Encryption Algorithm E Decryption Algorithm D Plain- text Plain- text Ciphertext INSECURE CHANNEL K K Secret Key shared by A and B SECURE CHANNEL A A B B
3 © Ravi Sandhu SECRET KEY CRYPTOSYSTEM confidentiality depends only on secrecy of the key size of key is critical secret key systems do not scale well with N parties we need to generate and distribute N*(N-1)/2 keys A and B can be people or computers
4 © Ravi Sandhu MASTER KEYS AND SESSION KEYS long-term or master keys prolonged use increases exposure session keys short-term keys communicated by means of long-term secret keys public key technology
5 © Ravi Sandhu CRYPTANALYSIS ciphertext only cryptanalyst only knows ciphertext known plaintext cryptanalyst knows some plaintext- ciphertext pairs chosen plaintext chosen ciphertext
6 © Ravi Sandhu KNOWN PLAINTEXT ATTACK 40 bit key requires 2 39 5 * 10 11 trials on average (exportable from USA) trials/secondtime required 120,000 years 10 3 20 years 10 6 6 days 10 9 9 minutes 10 12 0.5 seconds
7 © Ravi Sandhu KNOWN PLAINTEXT ATTACK 56 bit key requires 2 55 3.6 * 10 ^16 trials on average (DES) trials/secondtime required 110 9 years 10 3 10 6 years 10 6 10 3 years 10 9 1 year 10 12 10 hours
8 © Ravi Sandhu KNOWN PLAINTEXT ATTACK 80 bit key requires 2 79 6 * 10 23 trials on average (SKIPJACK) trials/secondtime required 110 16 years 10 3 10 13 years 10 6 10 10 years 10 9 10 7 years 10 12 10 4 years
9 © Ravi Sandhu KNOWN PLAINTEXT ATTACK 128 bit key requires 2 127 2 * 10 38 trials on average (IDEA) trials/secondtime required 110 30 years 10 3 10 27 years 10 6 10 24 years 10 9 10 21 years 10 12 10 18 years
10 © Ravi Sandhu DICTIONARY ATTACKS if keys are poorly chosen known plaintext attacks can be very simple often the users password is the key in a dictionary attack the cryptanalyst tries passwords from a dictionary, rather than all possible keys for a 20,000 word dictionary, 1 trial/second will crack a poor password in less than 3 hours
11 © Ravi Sandhu CURRENT GENERATION SECRET KEY CRYPTOSYSTEMS 64 bit data block size DES: 56 bit key Triple DES: 112 bit key Triple DES: 168 bit key Skipjack: 80 bit key IDEA: 128 bit key RC2: variable size key: 1 byte to 128 bytes many others
12 © Ravi Sandhu DOUBLE DES effective key size is only 57 bits due to meet- in-the-middle attack E E Plain- text Cipher- text Intermediate Ciphertext K1K2
13 © Ravi Sandhu TRIPLE DES effective key size is 112 bits due to meet-in- the-middle attack E D Plain- text Cipher- text K1K2 E K1
14 © Ravi Sandhu PERFECT SECRECY VERNAM ONE-TIME PAD Plain- text Plain- text Ciphertext KiSecret Key + Mi Ci + Ki Mi SECURE CHANNEL A B 0 0 0 0 1 1 1 0 1 1 1 0 A B 0 0 0 0 1 1 1 0 1 1 1 0
15 © Ravi Sandhu PERFECT SECRECY VERNAM ONE-TIME PAD known plaintext reveals the portion of the key that has been used, but does not reveal anything about the future bits of the key has been used can be approximated
16 © Ravi Sandhu ADVANCED ENCRYPTION STANDARD New Advanced Encryption Standard under development by NIST must support key-block combinations of 128- 128, 192-128, 256-128 may support other combinations selection of Rijndaehl algorithm announced in 2000 will be in place in a couple of years
17 © Ravi Sandhu ELECTRONIC CODE BOOK (ECB) MODE E 64 bit Data block 56 bit key D 64 bit Data block OK for small messages identical data blocks will be identically encrypted
18 © Ravi Sandhu CIPHER BLOCK CHAINING (CBC) MODE E 64 bit Data block 56 bit key D 64 bit Data block + + 64 bit previous ciphertext block 64 bit previous ciphertext block is the exclusive OR operation
19 © Ravi Sandhu CIPHER BLOCK CHAINING (CBC) MODE Needs an Initialization Vector (IV) to serve as the first feedback block IV need not be secret or random Integrity of the IV is important, otherwise first data block can be arbitrarily changed. IV should be changed from message to message, or first block of every message should be distinct
PKI Introduction Ravi Sandhu 2 © Ravi Sandhu 2002 CRYPTOGRAPHIC TECHNOLOGY PROS AND CONS SECRET KEY SYMMETRIC KEY Faster Not scalable No digital signatures.
Block Cipher Modes of Operation and Stream Ciphers CSE 651: Introduction to Network Security.
CLASSICAL ENCRYPTION TECHNIQUES
1 DES The Data Encryption Standard (DES) is a classic symmetric block cipher algorithm. DES was developed in the 1970s as a US government standard The.
ECE454/CS594 Computer and Network Security Dr. Jinyuan (Stella) Sun Dept. of Electrical Engineering and Computer Science University of Tennessee Fall 2011.
SYMMETRIC CRYPTOSYSTEMS Symmetric Cryptosystems 6/05/2014 | pag. 2.
Chapter 4: Modes of Operation CS 472: Fall Encrypting a Large Massage 1.Electronic Code Book (ECB) 2.Cipher Block Chaining (CBC) 3.Output Feedback.
25 seconds left….. 24 seconds left….. 23 seconds left…..
WEEK 1 You have 10 seconds to name…
Modes of Operation CS 795. Electronic Code Book (ECB) Each block of the message is encrypted with the same secret key Problems: If two identical blocks.
Addition 1’s to
We will resume in: 25 Minutes We will resume in: 24 Minutes.
FACTORING Think unfoil Work down, Show all steps ax 2 + bx + c.
L8. Reviews Rocky K. C. Chang, May Foci of this course 2 Rocky K. C. Chang Understand the 3 fundamental cryptographic functions and how they are.
1 Pretty Good Privacy (PGP) Security for Electronic .
Dr. Reuven Aviv, Nov 2008 Conventional Encryption 1 Conventional Encryption & Message Confidentiality Acknowledgements for slides Henric Johnson Blekinge.
Addition Facts = = =
“Advanced Encryption Standard” & “Modes of Operation”
1 Symmetric key cryptography: DES DES: Data Encryption Standard US encryption standard [NIST 1993] 56-bit symmetric key, 64 bit plaintext input How secure.
Jeopardy Topic 1Topic Q 1Q 6Q 11Q 16Q 21 Q 2Q 7Q 12Q 17Q 22 Q 3Q 8Q 13Q 18Q 23 Q 4Q 9Q 14Q 19Q 24 Q 5Q 10Q 15Q 20Q 25 Final Jeopardy.
6.1.2 Overview DES is a block cipher, as shown in Figure 6.1.
30.1 Chapter 30 Cryptography Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Symmetric Message Authentication Codes Prof. Ravi Sandhu.
ISA 662 IKE Key management for IPSEC Prof. Ravi Sandhu.
Asymmetric Encryption Prof. Ravi Sandhu. 2 © Ravi Sandhu PUBLIC KEY ENCRYPTION Encryption Algorithm E Decryption Algorithm D Plain- text Plain- text Ciphertext.
Time for a BREAK! You have 45 Minutes. Time Left 44.
Lecture 23 Symmetric Encryption modified from slides of Lawrie Brown.
Block Cipher Modes Last Updated: Aug 25, ECB Mode Electronic Code Book Divide the plaintext into fixed-size blocks Encrypt/Decrypt each block independently.
PUBLIC KEY CRYPTOSYSTEMS Symmetric Cryptosystems 6/05/2014 | pag. 2.
BLOCK CIPHER SYSTEMS OPERATION MODES OF DATA ENCRYPTION STANDARD (DES)
CS 483 – SD SECTION BY DR. DANIYAL ALGHAZZAWI (3) Information Security.
TWO STEP EQUATIONS 1. SOLVE FOR X 2. DO THE ADDITION STEP FIRST
by D. Fisher (2 + 1) + 4 = 2 + (1 + 4) Associative Property of Addition 1.
ISA 662 Internet Security Protocols Kerberos Prof. Ravi Sandhu.
1 International Data Encryption Algorithm By How-Shen Chang.
Modes of Usage Dan Fleck CS 469: Security Engineering These slides are modified with permission from Bill Young (Univ of Texas) 11 Coming up: Modes of.
Lets play bingo!!. Calculate: MEAN Calculate: MEDIAN
The Data Encryption Standard - see Susan Landau’s paper: “Standing the test of time: the data encryption standard.” DES - adopted in 1977 as a standard.
1 Cryptography encryption authentication digital signatures one-way functions hash algorithms key generation, exchange and management.
EEC 693/793 Special Topics in Electrical Engineering Secure and Dependable Computing Lecture 5 Wenbing Zhao Department of Electrical and Computer Engineering.
Adding Up In Chunks. Category 1 Adding multiples of ten to any number.
Copyright © 2012, Elsevier Inc. All rights Reserved. 1 Chapter 7 Modeling Structure with Blocks.
Cryptography Ch-1 prepared by: Diwan.
×1= 9 4 1×1= 1 5 8×1= 8 6 7×1= 7 7 8×3= 24.
1 Overview of the DES A block cipher: –encrypts blocks of 64 bits using a 64 bit key –outputs 64 bits of ciphertext A product cipher –basic unit is the.
From Crypto-Theory to Crypto-Practice 1 CHAPTER 14: From Crypto-Theory to Crypto-Practice SHIFT REGISTERS The first practical approach to ONE-TIME PAD.
Title Subtitle 1. A. B. C. C. * D. Click to try again! INCORRECT.
© 2017 SlidePlayer.com Inc. All rights reserved.