DES is a symmetric-key block cipher published by NIST. It uses a 56-bit key to encrypt 64-bit blocks. DES has an initial and final permutation, and uses 16 rounds of encryption with subkeys generated from the main key. Each round includes expansion, XOR with a subkey, S-boxes for substitution, and permutation. Analysis has shown DES exhibits the avalanche effect but has weaknesses due to its key size and structure.
DES is a block cipher that uses an initial and final permutation, along with 16 rounds of encryption. Each round uses a 48-bit key and includes expansion, XOR with the round key, processing by 8 S-boxes, and a final straight permutation. The initial and final permutations are inverses that do not impact cryptography, while the rounds mix the bits through expansion, XOR with subkeys, and S-boxes.
This document summarizes a chapter about the Data Encryption Standard (DES). It provides an overview of DES, describing it as a symmetric-key block cipher developed by IBM and adopted by the National Institute of Standards and Technology. The chapter then goes into details about the structure and design of DES, including its use of an initial and final permutation, 16 rounds of encryption using subkey values, and weaknesses like its short key length. It also discusses analyses of DES security, noting brute force, differential cryptanalysis, and linear cryptanalysis as potential attack methods.
This document provides an overview of the Data Encryption Standard (DES). It discusses the history and basic structure of DES, including the initial and final permutations, 16 rounds of encryption, and key generation process. It also analyzes the properties and design criteria of DES, and describes some weaknesses such as brute force attacks breaking it with 255 encryptions. Finally, it discusses ways to strengthen DES such as double and triple DES to increase the effective key size.
This document provides details about the structure and design of the Data Encryption Standard (DES) cipher. It describes the operation of DES, including the use of substitution boxes (S-boxes) and permutation boxes (P-boxes) to provide confusion and diffusion in the cipher. It also discusses some weaknesses that have been found in DES, such as specific weak keys that allow plaintext to be recovered more easily. The document aims to explain the design principles and security properties of DES.
The document discusses the Advanced Encryption Standard (AES) algorithm, which is used for encryption and involves several processes applied to a rectangular array called the state. AES uses a variable number of rounds depending on the key size, with each round consisting of sub bytes, shift rows, mix columns, and add round key transformations except for the last round which excludes mix columns. The Rijndael cipher which was selected as the AES algorithm operates on a 4x4 byte state and supports key sizes of 128, 192, and 256 bits.
The document discusses binary numbers and how computers use binary to represent data. It explains that computers use a two-state system of 1s and 0s because it is simple, tolerant to degradation, has simple calculation rules, and magnetic media can easily represent two states. It provides examples of converting binary numbers to decimal and decimal numbers to binary, illustrating how binary works in a similar place value system as decimal.
DES is a block cipher that uses an initial and final permutation, along with 16 rounds of encryption. Each round uses a 48-bit key and includes expansion, XOR with the round key, processing by 8 S-boxes, and a final straight permutation. The initial and final permutations are inverses that do not impact cryptography, while the rounds mix the bits through expansion, XOR with subkeys, and S-boxes.
This document summarizes a chapter about the Data Encryption Standard (DES). It provides an overview of DES, describing it as a symmetric-key block cipher developed by IBM and adopted by the National Institute of Standards and Technology. The chapter then goes into details about the structure and design of DES, including its use of an initial and final permutation, 16 rounds of encryption using subkey values, and weaknesses like its short key length. It also discusses analyses of DES security, noting brute force, differential cryptanalysis, and linear cryptanalysis as potential attack methods.
This document provides an overview of the Data Encryption Standard (DES). It discusses the history and basic structure of DES, including the initial and final permutations, 16 rounds of encryption, and key generation process. It also analyzes the properties and design criteria of DES, and describes some weaknesses such as brute force attacks breaking it with 255 encryptions. Finally, it discusses ways to strengthen DES such as double and triple DES to increase the effective key size.
This document provides details about the structure and design of the Data Encryption Standard (DES) cipher. It describes the operation of DES, including the use of substitution boxes (S-boxes) and permutation boxes (P-boxes) to provide confusion and diffusion in the cipher. It also discusses some weaknesses that have been found in DES, such as specific weak keys that allow plaintext to be recovered more easily. The document aims to explain the design principles and security properties of DES.
The document discusses the Advanced Encryption Standard (AES) algorithm, which is used for encryption and involves several processes applied to a rectangular array called the state. AES uses a variable number of rounds depending on the key size, with each round consisting of sub bytes, shift rows, mix columns, and add round key transformations except for the last round which excludes mix columns. The Rijndael cipher which was selected as the AES algorithm operates on a 4x4 byte state and supports key sizes of 128, 192, and 256 bits.
The document discusses binary numbers and how computers use binary to represent data. It explains that computers use a two-state system of 1s and 0s because it is simple, tolerant to degradation, has simple calculation rules, and magnetic media can easily represent two states. It provides examples of converting binary numbers to decimal and decimal numbers to binary, illustrating how binary works in a similar place value system as decimal.
This document provides information about decimal and binary number systems. It discusses how decimal numbers like 42678 represent quantities in terms of places values of tens, hundreds, thousands, etc. It then introduces the binary number system which uses only two digits, 0 and 1, to represent numbers in computers. The key advantages of the binary system for computers are its simplicity with only two states, good noise tolerance, simple calculations, and suitability for magnetic and optical storage media which also use two states. The document explains how to convert between decimal and binary numbers by representing them as place values and using addition and subtraction.
The document discusses the Data Encryption Standard (DES) algorithm. It describes how DES encrypts data in 64-bit blocks using a 56-bit key. The encryption process involves an initial permutation of the plaintext bits, followed by 16 rounds of substitution and transposition using 48-bit round keys generated from the original key. Finally, the ciphertext is produced after a final permutation.
Information and network security 20 data encryption standard desVaibhav Khanna
ย
The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for applications, it has been highly influential in the advancement of cryptography.
This document discusses various topics related to digital representation of data including:
1. The differences between FAT32 and NTFS file systems and their advantages and limitations.
2. How data is represented digitally using coding schemes like ASCII and converted between binary and other number systems.
3. An overview of different numbering systems including binary, decimal, octal and hexadecimal; and how to convert between them.
This document discusses various topics related to digital representation of data including:
1. The differences between FAT32 and NTFS file systems and their advantages and limitations.
2. How data is represented digitally using coding schemes like ASCII and converted between binary and other number systems.
3. An overview of different numbering systems including binary, decimal, octal and hexadecimal; and how to convert between them.
This document provides an overview of block ciphers and the Data Encryption Standard (DES) algorithm. It begins with definitions of stream ciphers and block ciphers. It then discusses the principles of confusion and diffusion in encryption algorithms. The document introduces the Feistel cipher structure and how it was developed based on Claude Shannon's work. It provides details on the DES algorithm, including its history, design, encryption process using rounds and subkeys, decryption process, and the avalanche effect property.
Abstract
There is great research going on in the field of data security nowadays. Protecting information from disclosure and breach is of high importance to users personally and to organizations and businesses around the world, as most of information currently are sensitive electronic information transferred over the internet and stored in cloud based system. In this paper, we propose a method to increase the security of messages transferred on the internet, or information stored in the cloud. Our proposed method mainly relies on the Triple Data Encryption Standard (TDES) algorithm. TDES is intact the Data Encryption Standard repeated three times in succession to encrypt data. TDES is considered highly secure as there is no applicable method to break the code itself without knowing the key. We propose to encrypt the key using Cipher Feedback Block algorithm, before using TDES to encrypt data. Such that even when the key is disclosed, the key itself cannot decipher the ciphered text without enciphering the key with CFB. This introduces a new dimension of security to the TDES algorithm.
The method introduced in this paper increases the security of the TDES algorithm using CFB algorithm by increasing the key security, such that it is actually not possible to decipher the text without prior knowledge and agreement of key and algorithms used.
Keywords: Data Encryption Standard, Triple Data Encryption Algorithm, Cipher Feedback Block.
Modern Block Cipher- Modern Symmetric-Key CipherMahbubur Rahman
ย
Introduction to Modern Symmetric-Key Ciphers- This lecture will cover only "Modern Block Cipher".
Slide Credit: Maleka Khatun & Mahbubur Rahman
Dept. of CSE, JnU, BD.
The document discusses decoders, multiplexers, and programmable logic. It begins by explaining what decoders and multiplexers are, providing examples of 2-to-4 and 3-to-8 decoders. It then discusses how decoders and multiplexers can be used to implement arbitrary logic functions. The document also covers variations of decoders, building decoders from smaller components, and using multiplexers to efficiently implement functions in a sum of minterms form.
This document discusses different number systems including binary, octal, decimal, and hexadecimal. It explains that each number system has a base, which indicates the number of symbols used. For example, the base of the binary system is 2 as it uses only 0 and 1, while the base of decimal is 10 as it uses 0-9. The document then provides steps for converting between these different number systems, such as using long division to break numbers down into place values for conversion. Examples are given of converting decimal, binary, octal, and hexadecimal numbers.
This document outlines the course content for a Higher Computing course, which is divided into 3 main units: Computer Systems (40 hours), Software Development (40 hours), and Artificial Intelligence (40 hours). The Computer Systems unit covers topics like data representation, computer structure, networking, and computer software across 5 sections. Specific lessons in the Data Representation section discuss how numbers, text, and images are stored in binary and how storage capacities are measured. Graphics representation and compression techniques are also introduced. Students will complete assessments including end of unit tests, coursework tasks, and a written exam.
This document outlines the course content for a Higher Computing course, which is divided into 3 main units: Computer Systems, Software Development, and Artificial Intelligence. The Computer Systems unit covers topics like data representation, computer structure, networking, and computer software. It discusses how numbers, text, images, and other data are stored in binary and converted between binary and decimal. It also covers graphics representation, storage calculations, and compression techniques. Assessment includes end of unit tests, coursework tasks, and a written exam.
This slide show illustrates how bits are used in computers, both as content and to organize information in memory. The show also illustrates how we use hexadecimal as a convenient notation for binary information. And it illustrates how the number of bits relates to the number of values that may be represented and how to estimate this number quickly without a calculator.
By Don Mendonsa,
Professor of IT and CS
Tidewater Community College
The document discusses different number systems including decimal, binary, octal, and hexadecimal. It provides details on the base, symbols used, positional notation, and conversions between the number systems. The key points covered are:
- Decimal uses base 10 with digits 0-9. Binary uses base 2 with digits 0-1. Octal uses base 8 with digits 0-7. Hexadecimal uses base 16 with digits 0-9 and A-F.
- Each system uses positional notation to represent values. Conversions between the systems involve dividing or multiplying by the base and tracking remainders or carries.
- Examples are provided of converting decimal values to and from the other bases through repetitive division or multiplication operations.
Data Encryption standard in cryptographyNithyasriA2
ย
The document discusses the Data Encryption Standard (DES) algorithm. It provides an overview of DES, including its history, encryption process, key generation process, and decryption process. It describes how DES uses a Feistel cipher structure with a 64-bit block size and 56-bit key. It also discusses various attacks that have been performed on DES, such as differential cryptanalysis and linear cryptanalysis, and how DES has been shown to be insecure due to increases in computational power allowing brute force attacks. Improved versions of DES using multiple encryptions, such as triple DES, are also summarized to increase the key size and security.
The document describes a symmetric encryption algorithm that uses:
- Substitution boxes (S-boxes) and permutation to encrypt message blocks
- A 40-bit key split into 5 8-bit subkeys to choose S-boxes and encrypt blocks
- Each block is encrypted in 5 rounds using XOR with subkey, S-box substitution, and permutation
The decryption process reverses the encryption steps using inverse S-boxes and permutations. The algorithm is implemented and tested encrypting/decrypting sample messages with no errors.
This document summarizes the key steps in the Data Encryption Standard (DES) encryption algorithm. DES is a block cipher that operates on 64-bit plaintext blocks, dividing each block into two 32-bit halves and performing permutations and substitutions using a 56-bit key to produce a ciphertext block. The document outlines how DES generates 16 subkeys from the main key through permutations, and uses these subkeys along with initial and final permutations of the plaintext block to encrypt the data through 16 iterations, XORing and substituting bits at each step.
This document presents the process for designing and implementing a 4-to-15 bit decoder circuit to display a 9-letter word on a 15-segment display. Karnaugh maps are used to simplify the logic expressions for each display segment. A truth table is constructed showing the logic values for each segment corresponding to the input codes needed to display the word "IMPOSTURA". Don't care conditions are applied to simplify the implementation.
The document discusses various computer-based symmetric key cryptographic algorithms and ciphers. It describes the basic mechanisms of stream ciphers and block ciphers, providing examples of each. It then explains several popular symmetric key algorithms in more detail, including DES, Triple DES, IDEA, Blowfish, RC5, and Rijndael (AES). For each algorithm, it outlines the basic encryption/decryption process and key aspects of the algorithm such as round structure, key scheduling, and substitution and permutation operations.
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
ย
(๐๐๐ ๐๐๐) (๐๐๐ฌ๐ฌ๐จ๐ง ๐)-๐๐ซ๐๐ฅ๐ข๐ฆ๐ฌ
๐๐ข๐ฌ๐๐ฎ๐ฌ๐ฌ ๐ญ๐ก๐ ๐๐๐ ๐๐ฎ๐ซ๐ซ๐ข๐๐ฎ๐ฅ๐ฎ๐ฆ ๐ข๐ง ๐ญ๐ก๐ ๐๐ก๐ข๐ฅ๐ข๐ฉ๐ฉ๐ข๐ง๐๐ฌ:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
๐๐ฑ๐ฉ๐ฅ๐๐ข๐ง ๐ญ๐ก๐ ๐๐๐ญ๐ฎ๐ซ๐ ๐๐ง๐ ๐๐๐จ๐ฉ๐ ๐จ๐ ๐๐ง ๐๐ง๐ญ๐ซ๐๐ฉ๐ซ๐๐ง๐๐ฎ๐ซ:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
More Related Content
Similar to cryptography2 WHICH IS VERY IMPOTRANT.pdf
This document provides information about decimal and binary number systems. It discusses how decimal numbers like 42678 represent quantities in terms of places values of tens, hundreds, thousands, etc. It then introduces the binary number system which uses only two digits, 0 and 1, to represent numbers in computers. The key advantages of the binary system for computers are its simplicity with only two states, good noise tolerance, simple calculations, and suitability for magnetic and optical storage media which also use two states. The document explains how to convert between decimal and binary numbers by representing them as place values and using addition and subtraction.
The document discusses the Data Encryption Standard (DES) algorithm. It describes how DES encrypts data in 64-bit blocks using a 56-bit key. The encryption process involves an initial permutation of the plaintext bits, followed by 16 rounds of substitution and transposition using 48-bit round keys generated from the original key. Finally, the ciphertext is produced after a final permutation.
Information and network security 20 data encryption standard desVaibhav Khanna
ย
The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for applications, it has been highly influential in the advancement of cryptography.
This document discusses various topics related to digital representation of data including:
1. The differences between FAT32 and NTFS file systems and their advantages and limitations.
2. How data is represented digitally using coding schemes like ASCII and converted between binary and other number systems.
3. An overview of different numbering systems including binary, decimal, octal and hexadecimal; and how to convert between them.
This document discusses various topics related to digital representation of data including:
1. The differences between FAT32 and NTFS file systems and their advantages and limitations.
2. How data is represented digitally using coding schemes like ASCII and converted between binary and other number systems.
3. An overview of different numbering systems including binary, decimal, octal and hexadecimal; and how to convert between them.
This document provides an overview of block ciphers and the Data Encryption Standard (DES) algorithm. It begins with definitions of stream ciphers and block ciphers. It then discusses the principles of confusion and diffusion in encryption algorithms. The document introduces the Feistel cipher structure and how it was developed based on Claude Shannon's work. It provides details on the DES algorithm, including its history, design, encryption process using rounds and subkeys, decryption process, and the avalanche effect property.
Abstract
There is great research going on in the field of data security nowadays. Protecting information from disclosure and breach is of high importance to users personally and to organizations and businesses around the world, as most of information currently are sensitive electronic information transferred over the internet and stored in cloud based system. In this paper, we propose a method to increase the security of messages transferred on the internet, or information stored in the cloud. Our proposed method mainly relies on the Triple Data Encryption Standard (TDES) algorithm. TDES is intact the Data Encryption Standard repeated three times in succession to encrypt data. TDES is considered highly secure as there is no applicable method to break the code itself without knowing the key. We propose to encrypt the key using Cipher Feedback Block algorithm, before using TDES to encrypt data. Such that even when the key is disclosed, the key itself cannot decipher the ciphered text without enciphering the key with CFB. This introduces a new dimension of security to the TDES algorithm.
The method introduced in this paper increases the security of the TDES algorithm using CFB algorithm by increasing the key security, such that it is actually not possible to decipher the text without prior knowledge and agreement of key and algorithms used.
Keywords: Data Encryption Standard, Triple Data Encryption Algorithm, Cipher Feedback Block.
Modern Block Cipher- Modern Symmetric-Key CipherMahbubur Rahman
ย
Introduction to Modern Symmetric-Key Ciphers- This lecture will cover only "Modern Block Cipher".
Slide Credit: Maleka Khatun & Mahbubur Rahman
Dept. of CSE, JnU, BD.
The document discusses decoders, multiplexers, and programmable logic. It begins by explaining what decoders and multiplexers are, providing examples of 2-to-4 and 3-to-8 decoders. It then discusses how decoders and multiplexers can be used to implement arbitrary logic functions. The document also covers variations of decoders, building decoders from smaller components, and using multiplexers to efficiently implement functions in a sum of minterms form.
This document discusses different number systems including binary, octal, decimal, and hexadecimal. It explains that each number system has a base, which indicates the number of symbols used. For example, the base of the binary system is 2 as it uses only 0 and 1, while the base of decimal is 10 as it uses 0-9. The document then provides steps for converting between these different number systems, such as using long division to break numbers down into place values for conversion. Examples are given of converting decimal, binary, octal, and hexadecimal numbers.
This document outlines the course content for a Higher Computing course, which is divided into 3 main units: Computer Systems (40 hours), Software Development (40 hours), and Artificial Intelligence (40 hours). The Computer Systems unit covers topics like data representation, computer structure, networking, and computer software across 5 sections. Specific lessons in the Data Representation section discuss how numbers, text, and images are stored in binary and how storage capacities are measured. Graphics representation and compression techniques are also introduced. Students will complete assessments including end of unit tests, coursework tasks, and a written exam.
This document outlines the course content for a Higher Computing course, which is divided into 3 main units: Computer Systems, Software Development, and Artificial Intelligence. The Computer Systems unit covers topics like data representation, computer structure, networking, and computer software. It discusses how numbers, text, images, and other data are stored in binary and converted between binary and decimal. It also covers graphics representation, storage calculations, and compression techniques. Assessment includes end of unit tests, coursework tasks, and a written exam.
This slide show illustrates how bits are used in computers, both as content and to organize information in memory. The show also illustrates how we use hexadecimal as a convenient notation for binary information. And it illustrates how the number of bits relates to the number of values that may be represented and how to estimate this number quickly without a calculator.
By Don Mendonsa,
Professor of IT and CS
Tidewater Community College
The document discusses different number systems including decimal, binary, octal, and hexadecimal. It provides details on the base, symbols used, positional notation, and conversions between the number systems. The key points covered are:
- Decimal uses base 10 with digits 0-9. Binary uses base 2 with digits 0-1. Octal uses base 8 with digits 0-7. Hexadecimal uses base 16 with digits 0-9 and A-F.
- Each system uses positional notation to represent values. Conversions between the systems involve dividing or multiplying by the base and tracking remainders or carries.
- Examples are provided of converting decimal values to and from the other bases through repetitive division or multiplication operations.
Data Encryption standard in cryptographyNithyasriA2
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The document discusses the Data Encryption Standard (DES) algorithm. It provides an overview of DES, including its history, encryption process, key generation process, and decryption process. It describes how DES uses a Feistel cipher structure with a 64-bit block size and 56-bit key. It also discusses various attacks that have been performed on DES, such as differential cryptanalysis and linear cryptanalysis, and how DES has been shown to be insecure due to increases in computational power allowing brute force attacks. Improved versions of DES using multiple encryptions, such as triple DES, are also summarized to increase the key size and security.
The document describes a symmetric encryption algorithm that uses:
- Substitution boxes (S-boxes) and permutation to encrypt message blocks
- A 40-bit key split into 5 8-bit subkeys to choose S-boxes and encrypt blocks
- Each block is encrypted in 5 rounds using XOR with subkey, S-box substitution, and permutation
The decryption process reverses the encryption steps using inverse S-boxes and permutations. The algorithm is implemented and tested encrypting/decrypting sample messages with no errors.
This document summarizes the key steps in the Data Encryption Standard (DES) encryption algorithm. DES is a block cipher that operates on 64-bit plaintext blocks, dividing each block into two 32-bit halves and performing permutations and substitutions using a 56-bit key to produce a ciphertext block. The document outlines how DES generates 16 subkeys from the main key through permutations, and uses these subkeys along with initial and final permutations of the plaintext block to encrypt the data through 16 iterations, XORing and substituting bits at each step.
This document presents the process for designing and implementing a 4-to-15 bit decoder circuit to display a 9-letter word on a 15-segment display. Karnaugh maps are used to simplify the logic expressions for each display segment. A truth table is constructed showing the logic values for each segment corresponding to the input codes needed to display the word "IMPOSTURA". Don't care conditions are applied to simplify the implementation.
The document discusses various computer-based symmetric key cryptographic algorithms and ciphers. It describes the basic mechanisms of stream ciphers and block ciphers, providing examples of each. It then explains several popular symmetric key algorithms in more detail, including DES, Triple DES, IDEA, Blowfish, RC5, and Rijndael (AES). For each algorithm, it outlines the basic encryption/decryption process and key aspects of the algorithm such as round structure, key scheduling, and substitution and permutation operations.
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(๐๐๐ ๐๐๐) (๐๐๐ฌ๐ฌ๐จ๐ง ๐)-๐๐ซ๐๐ฅ๐ข๐ฆ๐ฌ
๐๐ข๐ฌ๐๐ฎ๐ฌ๐ฌ ๐ญ๐ก๐ ๐๐๐ ๐๐ฎ๐ซ๐ซ๐ข๐๐ฎ๐ฅ๐ฎ๐ฆ ๐ข๐ง ๐ญ๐ก๐ ๐๐ก๐ข๐ฅ๐ข๐ฉ๐ฉ๐ข๐ง๐๐ฌ:
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Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
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2. Objectives
Chapter 6
โ To review a short history of DES
y
โ To define the basic structure of DES
โ To describe the details of building elements of DES
โ To describe the round keys generation process
โ To analyze DES
6.2
3. 6
6-
-1 INTRODUCTION
1 INTRODUCTION
The
The Data
Data Encryption
Encryption Standard
Standard (DES)
(DES) is
is a
a symmetric
symmetric-
-
k
k bl k
bl k i h
i h bli h d
bli h d b
b h
h N i l
N i l I i
I i f
f
key
key block
block cipher
cipher published
published by
by the
the National
National Institute
Institute of
of
Standards
Standards and
and Technology
Technology (NIST)
(NIST).
.
Topics discussed in this section:
Topics discussed in this section:
6.1.1 History
6.1.2 Overview
6.3
4. 6.1.1 History
In 1973, NIST published a request for proposals for a
national symmetric-key cryptosystem. A proposal from
y y yp y p p f
IBM, a modification of a project called Lucifer, was
accepted as DES. DES was published in the Federal
Register in March 1975 as a draft of the Federal
Information Processing Standard (FIPS).
6.4
5. 6.1.2 Overview
DES is a block cipher, as shown in Figure 6.1.
Figure 6.1 Encryption and decryption with DES
6.5
6. 6
6-
-2 DES STRUCTURE
2 DES STRUCTURE
The
The encryption
encryption process
process is
is made
made of
of two
two permutations
permutations
(P
(P-
-boxes),
boxes), which
which we
we call
call initial
initial and
and final
final
(P
(P boxes),
boxes), which
which we
we call
call initial
initial and
and final
final
permutations,
permutations, and
and sixteen
sixteen Feistel
Feistel rounds
rounds.
.
Topics discussed in this section:
Topics discussed in this section:
6.2.1 Initial and Final Permutations
6.2.2 Rounds
6.2.3 Cipher and Reverse Cipher
6.6
p p
6.2.4 Examples
8. 6.2.1 Initial and Final Permutations
Figure 6.3 Initial and final permutation steps in DES
6.8
9. 6.2.1 Continue
Table 6 1 Initial and final permutation tables
Table 6.1 Initial and final permutation tables
6.9
10. 6.2.1 Continued
Example 6.1
Find
Find the
the output
output of
of the
the initial
initial permutation
permutation box
box when
when the
the input
input
is
is given
given in
in hexadecimal
hexadecimal as
as:
:
Solution
Solution
Only
Only bit
bit 25
25 and
and bit
bit 64
64 are
are 1
1s
s;
; the
the other
other bits
bits are
are 0
0s
s.
. In
In the
the final
final
permutation,
permutation, bit
bit 25
25 becomes
becomes bit
bit 64
64 and
and bit
bit 63
63 becomes
becomes bit
bit 15
15.
.
The
The result
result is
is
The
The result
result is
is
6.10
11. 6.2.1 Continued
Example 6.2
Prove
Prove that
that the
the initial
initial and
and final
final permutations
permutations are
are the
the inverse
inverse
p
p
of
of each
each other
other by
by finding
finding the
the output
output of
of the
the final
final permutation
permutation if
if
the
the input
input is
is
Solution
Solution
The
The input
input has
has only
only two
two 1
1s
s;
; the
the output
output must
must also
also have
have only
only two
two
1
1s
s.
. Using
Using Table
Table 6
6.
.1
1,
, we
we can
can find
find the
the output
output related
related to
to these
these
two
two bits
bits Bit
Bit 15
15 in
in the
the input
input becomes
becomes bit
bit 63
63 in
in the
the output
output Bit
Bit
two
two bits
bits.
. Bit
Bit 15
15 in
in the
the input
input becomes
becomes bit
bit 63
63 in
in the
the output
output.
. Bit
Bit
64
64 in
in the
the input
input becomes
becomes bit
bit 25
25 in
in the
the output
output.
. So
So the
the output
output
has
has only
only two
two 1
1s,
s, bit
bit 25
25 and
and bit
bit 63
63.
. The
The result
result in
in hexadecimal
hexadecimal is
is
6.11
12. 6.2.1 Continued
Note
The initial and final permutations are
straight P-boxes that are inverses
of each other.
They have no cryptography significance in
DES.
6.12
13. 6.2.2 Rounds
DES uses 16 rounds. Each round of DES is a Feistel
cipher.
Fi 6 4
Figure 6.4
A round in DES
(encryption site)
6.13
14. 6.2.2 Continued
DES Function
The heart of DES is the DES function. The DES function
applies a 48-bit key to the rightmost 32 bits to produce a
32-bit output.
Figure 6.5
DES function
6.14
15. 6.2.2 Continue
Expansion P-box
Since RIโ1 is a 32-bit input and KI is a 48-bit key, we first
need to expand RIโ1 to 48 bits.
Figure 6.6 Expansion permutation
6.15
16. 6.2.2 Continue
Although the relationship between the input and output
can be defined mathematically, DES uses Table 6.2 to
define this P-box.
Table 6 6 Expansion P box table
Table 6.6 Expansion P-box table
6.16
17. 6.2.2 Continue
Whitener (XOR)
After the expansion permutation, DES uses the XOR
operation on the expanded right section and the round
key. Note that both the right section and the key are 48-
bits in length. Also note that the round key is used only in
this operation.
6.17
18. 6.2.2 Continue
S-Boxes
The S-boxes do the real mixing (confusion). DES uses 8
S-boxes, each with a 6-bit input and a 4-bit output. See
Figure 6.7.
Figure 6.7 S-boxes
6.18
20. Table 6 3 shows the permutation for S box 1 For the rest
6.2.2 Continue
Table 6.3 shows the permutation for S-box 1. For the rest
of the boxes see the textbook.
Table 6.3 S-box 1
6.20
21. Example 6.3
6.2.2 Continued
The
The input
input to
to S
S-
-box
box 1
1 is
is 1
10001
00011
1.
. What
What is
is the
the output?
output?
If
If we
we write
write the
the first
first and
and the
the sixth
sixth bits
bits together,
together, we
we get
get 11
11 in
in
bi
bi hi h
hi h i
i 3
3 i
i d i l
d i l Th
Th i i
i i bit
bit 0001
0001 i
i
Solution
Solution
binary,
binary, which
which is
is 3
3 in
in decimal
decimal.
. The
The remaining
remaining bits
bits are
are 0001
0001 in
in
binary,
binary, which
which is
is 1
1 in
in decimal
decimal.
. We
We look
look for
for the
the value
value in
in row
row 3
3,
,
column
column 1
1,
, in
in Table
Table 6
6.
.3
3 (S
(S-
-box
box 1
1)
).
. The
The result
result is
is 12
12 in
in decimal,
decimal,
which
which in
in binary
binary is
is 1100
1100.
. So
So the
the input
input 100011
100011 yields
yields the
the output
output
1100
1100.
.
6.21
22. Example 6.4
6.2.2 Continued
The
The input
input to
to S
S-
-box
box 8
8 is
is 000000
000000.
. What
What is
is the
the output?
output?
If
If we
we write
write the
the first
first and
and the
the sixth
sixth bits
bits together,
together, we
we get
get 00
00 in
in
bi
bi hi h
hi h i
i 0
0 i
i d i l
d i l Th
Th i i
i i bit
bit 0000
0000 i
i
Solution
Solution
binary,
binary, which
which is
is 0
0 in
in decimal
decimal.
. The
The remaining
remaining bits
bits are
are 0000
0000 in
in
binary,
binary, which
which is
is 0
0 in
in decimal
decimal.
. We
We look
look for
for the
the value
value in
in row
row 0
0,
,
column
column 0
0,
, in
in Table
Table 6
6.
.10
10 (S
(S-
-box
box 8
8)
).
. The
The result
result is
is 13
13 in
in decimal,
decimal,
which
which is
is 1101
1101 in
in binary
binary.
. So
So the
the input
input 000000
000000 yields
yields the
the output
output
1101
1101.
.
6.22
24. 6.2.3 Cipher and Reverse Cipher
Using mixers and swappers, we can create the cipher and
reverse cipher, each having 16 rounds.
First Approach
T hi thi l h i t k th l t
To achieve this goal, one approach is to make the last
round (round 16) different from the others; it has only a
mixer and no swapper
mixer and no swapper.
Note
In the first approach, there is no swapper in
Note
6.24
the last round.
30. 6.2.3 Continued
Alternative Approach
We can make all 16 rounds the same by including one
We can make all 16 rounds the same by including one
swapper to the 16th round and add an extra swapper after
that (two swappers cancel the effect of each other).
( pp ff f )
Key Generation
Key Generation
The round-key generator creates sixteen 48-bit keys out
of a 56 bit cipher key
of a 56-bit cipher key.
6.30
36. Example 6.5
6.2.4 Examples
We
We choose
choose a
a random
random plaintext
plaintext block
block and
and a
a random
random key,
key, and
and
determine
determine what
what the
the ciphertext
ciphertext block
block would
would be
be (all
(all in
in
hexadecimal)
hexadecimal):
:
Table 6.15 Trace of data for Example 6.5
6.36
38. Example 6.6
6.2.4 Continued
Let
Let us
us see
see how
how Bob,
Bob, at
at the
the destination,
destination, can
can decipher
decipher the
the
ciphertext
ciphertext received
received from
from Alice
Alice using
using the
the same
same key
key.
. Table
Table 6
6.
.16
16
shows
shows some
some interesting
interesting points
points.
.
6.38
39. 6
6-
-3 DES ANALYSIS
3 DES ANALYSIS
Critics
Critics have
have used
used a
a strong
strong magnifier
magnifier to
to analyze
analyze DES
DES.
.
Tests
Tests have
have been
been done
done to
to measure
measure the
the strength
strength of
of some
some
Tests
Tests have
have been
been done
done to
to measure
measure the
the strength
strength of
of some
some
desired
desired properties
properties in
in a
a block
block cipher
cipher.
.
Topics discussed in this section:
Topics discussed in this section:
6.3.1 Properties
6.3.2 Design Criteria
6.3.3 DES Weaknesses
6.39
40. 6.3.1 Properties
Two desired properties of a block cipher are the
avalanche effect and the completeness.
Example 6.7
To
To check
check the
the avalanche
avalanche effect
effect in
in DES,
DES, let
let us
us encrypt
encrypt two
two
plaintext
plaintext blocks
blocks (with
(with the
the same
same key)
key) that
that differ
differ only
only in
in one
one bit
bit
d
d b
b h
h diff
diff i
i h
h b
b f
f bi
bi i
i h
h
and
and observe
observe the
the differences
differences in
in the
the number
number of
of bits
bits in
in each
each
round
round.
.
6.40
41. Example 6.7
6.3.1 Continued
Continued
Although
Although the
the two
two plaintext
plaintext blocks
blocks differ
differ only
only in
in the
the rightmost
rightmost
bit,
bit, the
the ciphertext
ciphertext blocks
blocks differ
differ in
in 29
29 bits
bits.
. This
This means
means that
that
bit,
bit, the
the ciphertext
ciphertext blocks
blocks differ
differ in
in 29
29 bits
bits.
. This
This means
means that
that
changing
changing approximately
approximately 1
1.
.5
5 percent
percent of
of the
the plaintext
plaintext creates
creates a
a
change
change of
of approximately
approximately 45
45 percent
percent in
in the
the ciphertext
ciphertext.
.
Table 6.17 Number of bit differences for Example 6.7
6.41
42. 6.3.1 Continued
Completeness effect
Completeness effect means that each bit of the ciphertext
Completeness effect means that each bit of the ciphertext
needs to depend on many bits on the plaintext.
6.42
43. 6.3.2 Design Criteria
S-Boxe
The design provides confusion and diffusion of bits from
h d t th t
each round to the next.
P-Boxes
h id diff i f bi
They provide diffusion of bits.
Number of Rounds
DES uses sixteen rounds of Feistel ciphers. the ciphertext
i th hl d f ti f l i t t d
is thoroughly a random function of plaintext and
ciphertext.
6.43
44. 6.3.3 DES Weaknesses
During the last few years critics have found some
weaknesses in DES.
Weaknesses in Cipher Design
1. Weaknesses in S-boxes
2 Weaknesses in P boxes
2. Weaknesses in P-boxes
3. Weaknesses in Key
6.44
45. Example 6.8
6.3.3 Continued
Let
Let us
us try
try the
the first
first weak
weak key
key in
in Table
Table 6
6.
.18
18 to
to encrypt
encrypt a
a block
block
two
two times
times.
. After
After two
two encryptions
encryptions
with
with the
the same
same key
key the
the original
original plaintext
plaintext block
block is
is created
created.
. Note
Note
that
that we
we have
have used
used the
the encryption
encryption algorithm
algorithm two
two times,
times, not
not
one
one encryption
encryption followed
followed by
by another
another decryption
decryption.
.
yp
yp y
y yp
yp
6.45
50. Example 6.9
6.3.3 Continued
What
What is
is the
the probability
probability of
of randomly
randomly selecting
selecting a
a weak,
weak, a
a semi
semi-
-
weak,
weak, or
or a
a possible
possible weak
weak key?
key?
,
, p
p y
y
Solution
Solution
56
56
DES
DES has
has a
a key
key domain
domain of
of 2
256
56.
. The
The total
total number
number of
of the
the above
above
keys
keys are
are 64
64 (
(4
4 +
+ 12
12 +
+ 48
48)
).
. The
The probability
probability of
of choosing
choosing one
one of
of
these
these keys
keys is
is 8
8.
.8
8 ร
ร 10
10โ
โ16
16,
, almost
almost impossible
impossible.
.
y
y ,
, p
p
6.50
52. Example 6.10
6.3.3 Continued
Let
Let us
us test
test the
the claim
claim about
about the
the complement
complement keys
keys.
. We
We have
have
used
used an
an arbitrary
arbitrary key
key and
and plaintext
plaintext to
to find
find the
the corresponding
corresponding
y
y y
y p
p p g
p g
ciphertext
ciphertext.
. If
If we
we have
have the
the key
key complement
complement and
and the
the plaintext,
plaintext,
we
we can
can obtain
obtain the
the complement
complement of
of the
the previous
previous ciphertext
ciphertext
(Table
(Table 6
6 20
20)
)
(Table
(Table 6
6.
.20
20)
).
.
6.52
53. 6
6-
-4 Multiple DES
4 Multiple DES
The
The major
major criticism
criticism of
of DES
DES regards
regards its
its key
key length
length.
.
Fortunately
Fortunately DES
DES is
is not
not a
a group
group.
. This
This means
means that
that we
we
Fortunately
Fortunately DES
DES is
is not
not a
a group
group.
. This
This means
means that
that we
we
can
can use
use double
double or
or triple
triple DES
DES to
to increase
increase the
the key
key size
size.
.
6.4.1 Double DES
6 4 4 T i l DES
Topics discussed in this section:
Topics discussed in this section:
6.53
6.4.4 Triple DES
54. 6
6-
-4 Continued
4 Continued
A
A substitution
substitution that
that maps
maps every
every possible
possible input
input to
to every
every
possible
possible output
output is
is a
a group
group.
.
Figure 6.13 Composition of mapping
6.54
55. 6.4.1 Double DES
The first approach is to use double DES (2DES).
Meet-in-the-Middle Attack
Meet in the Middle Attack
However, using a known-plaintext attack called meet-in-
the-middle attack proves that double DES improves this
vulnerability slightly (to 257 tests), but not tremendously
(to 2112).
6.55
56. 6.4.1 Continued
Figure 6 14 Meet-in-the-middle attack for double DES
Figure 6.14 Meet-in-the-middle attack for double DES
6.56
59. 6.4.2 Continuous
Triple DES with Three Keys
The possibility of known-plaintext attacks on triple DES
with two keys has enticed some applications to use triple
DES with three keys. Triple DES with three keys is used
by many applications such as PGP (See Chapter 16)
by many applications such as PGP (See Chapter 16).
6.59
60. 6
6-
-5 Security of DES
5 Security of DES
DES,
DES, as
as the
the first
first important
important block
block cipher,
cipher, has
has gone
gone
through
through much
much scrutiny
scrutiny Among
Among the
the attempted
attempted attacks
attacks
through
through much
much scrutiny
scrutiny.
. Among
Among the
the attempted
attempted attacks,
attacks,
three
three are
are of
of interest
interest:
: brute
brute-
-force,
force, differential
differential
cryptanalysis,
cryptanalysis, and
and linear
linear cryptanalysis
cryptanalysis.
.
yp y
yp y yp y
yp y
Topics discussed in this section:
Topics discussed in this section:
6.5.1 Brute-Force Attack
6.5.2 Differential Cryptanalysis
6.5.3 Linear Cryptanalysis
6.60
yp y
61. 6.5.1 Brute-Force Attack
We have discussed the weakness of short cipher key in
DES. Combining this weakness with the key complement
k it i l th t DES b b k i 255
weakness, it is clear that DES can be broken using 255
encryptions.
6.61
62. 6.5.2 Differential Cryptanalysis
It has been revealed that the designers of DES already
knew about this type of attack and designed S-boxes and
h 16 th b f d t k DES
chose 16 as the number of rounds to make DES
specifically resistant to this type of attack.
Note
We show an example of DES differential
cryptanalysis in Appendix N
cryptanalysis in Appendix N.
6.62
63. 6.5.3 Linear Cryptanalysis
Linear cryptanalysis is newer than differential
cryptanalysis. DES is more vulnerable to linear
cryptanalysis than to differential cryptanalysis S boxes
cryptanalysis than to differential cryptanalysis. S-boxes
are not very resistant to linear cryptanalysis. It has been
shown that DES can be broken using 243 pairs of known
s ow t at S ca be b o e usi g pai s of ow
plaintexts. However, from the practical point of view,
finding so many pairs is very unlikely.
Note
We show an example of DES linear
cryptanalysis in Appendix N
6.63
cryptanalysis in Appendix N.