This document discusses computer security and cryptography. It covers the basics of cryptography including the needs for secure communication, encryption algorithms, symmetric and asymmetric encryption, encryption standards like DES and AES, cryptanalysis techniques, and authentication methods. It provides an overview of the key concepts and techniques in cryptography.
This document discusses computer security and cryptography. It covers the basic needs and requirements of secure communication such as secrecy, authentication, and message integrity. It then describes the basics of cryptography including encryption algorithms, keys, symmetric and asymmetric encryption. Specific encryption algorithms covered include DES, Triple DES, Blowfish and AES. Cryptanalysis techniques for breaking encryption codes are also summarized. The document provides an overview of computer security and cryptography concepts.
Cryptography is the science of secure and hidden communication. It has two main components - encryption and authentication & integrity. Encryption involves hiding messages so that only the intended recipient can read them, while authentication & integrity ensures users are who they claim to be and messages are not altered. Popular symmetric encryption algorithms like DES and AES use the same key for encryption and decryption, while asymmetric algorithms like RSA use different public and private keys to encrypt and decrypt. Cryptanalysis involves analyzing and attempting to break encryption methods.
This document provides an overview of cryptography and network security concepts. It discusses computer security, network security, and internet security. It then covers security attacks like passive attacks which obtain transmitted information and active attacks which modify data. Security services like authentication, access control, and data confidentiality are explained. Security mechanisms like encipherment, digital signatures, and traffic padding are also introduced. Symmetric ciphers like the Caesar cipher, monoalphabetic cipher, Playfair cipher, polyalphabetic ciphers, and the one-time pad are described. Block ciphers principles involving confusion and diffusion are covered. The Data Encryption Standard (DES) cipher is explained in detail regarding its history, structure using Feistel networks, key size,
The document discusses various topics in cryptography and network security. It introduces symmetric and asymmetric encryption techniques, including classical ciphers, block ciphers like AES, and key distribution challenges. It also covers hash functions, digital signatures, authentication protocols and firewalls for network security. The goal is to classify attacks and understand modern cryptographic algorithms and security mechanisms.
Cryptography involves encrypting data using algorithms and keys to protect confidentiality, integrity, and authenticity. The document discusses the history and evolution of cryptography from manual ciphers to modern computer-based methods. It provides an overview of symmetric and asymmetric encryption techniques, and describes the Data Encryption Standard (DES) and its replacement by the Advanced Encryption Standard (AES).
Information security powerpoint presentationMuneebZahid10
The document defines several basic cryptographic concepts and classical encryption techniques. It discusses cryptography, cryptanalysis, cryptology, cryptographic systems, and classes of cryptographic systems including unkeyed, secret key, and public key systems. It then covers classical techniques like the Caesar cipher, Playfair cipher, Vigenere cipher, transposition ciphers, the One-Time Pad, and rotor machines. Frequency analysis is also introduced as a cryptanalysis technique to break simple substitution ciphers.
This document discusses cryptographic techniques used for secure communication. It defines cryptography as the art of secret coding to provide confidentiality, integrity, authentication, and non-repudiation. The two main techniques are symmetric encryption, which uses a shared secret key, and asymmetric encryption, which uses public and private key pairs. Common symmetric algorithms discussed are AES, DES, and Blowfish, while asymmetric algorithms include RSA and Diffie-Hellman key exchange. The goal of cryptography is to provide security services like confidentiality, integrity, authentication, non-repudiation, availability, and access control.
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This document discusses computer security and cryptography. It covers the basic needs and requirements of secure communication such as secrecy, authentication, and message integrity. It then describes the basics of cryptography including encryption algorithms, keys, symmetric and asymmetric encryption. Specific encryption algorithms covered include DES, Triple DES, Blowfish and AES. Cryptanalysis techniques for breaking encryption codes are also summarized. The document provides an overview of computer security and cryptography concepts.
Cryptography is the science of secure and hidden communication. It has two main components - encryption and authentication & integrity. Encryption involves hiding messages so that only the intended recipient can read them, while authentication & integrity ensures users are who they claim to be and messages are not altered. Popular symmetric encryption algorithms like DES and AES use the same key for encryption and decryption, while asymmetric algorithms like RSA use different public and private keys to encrypt and decrypt. Cryptanalysis involves analyzing and attempting to break encryption methods.
This document provides an overview of cryptography and network security concepts. It discusses computer security, network security, and internet security. It then covers security attacks like passive attacks which obtain transmitted information and active attacks which modify data. Security services like authentication, access control, and data confidentiality are explained. Security mechanisms like encipherment, digital signatures, and traffic padding are also introduced. Symmetric ciphers like the Caesar cipher, monoalphabetic cipher, Playfair cipher, polyalphabetic ciphers, and the one-time pad are described. Block ciphers principles involving confusion and diffusion are covered. The Data Encryption Standard (DES) cipher is explained in detail regarding its history, structure using Feistel networks, key size,
The document discusses various topics in cryptography and network security. It introduces symmetric and asymmetric encryption techniques, including classical ciphers, block ciphers like AES, and key distribution challenges. It also covers hash functions, digital signatures, authentication protocols and firewalls for network security. The goal is to classify attacks and understand modern cryptographic algorithms and security mechanisms.
Cryptography involves encrypting data using algorithms and keys to protect confidentiality, integrity, and authenticity. The document discusses the history and evolution of cryptography from manual ciphers to modern computer-based methods. It provides an overview of symmetric and asymmetric encryption techniques, and describes the Data Encryption Standard (DES) and its replacement by the Advanced Encryption Standard (AES).
Information security powerpoint presentationMuneebZahid10
The document defines several basic cryptographic concepts and classical encryption techniques. It discusses cryptography, cryptanalysis, cryptology, cryptographic systems, and classes of cryptographic systems including unkeyed, secret key, and public key systems. It then covers classical techniques like the Caesar cipher, Playfair cipher, Vigenere cipher, transposition ciphers, the One-Time Pad, and rotor machines. Frequency analysis is also introduced as a cryptanalysis technique to break simple substitution ciphers.
This document discusses cryptographic techniques used for secure communication. It defines cryptography as the art of secret coding to provide confidentiality, integrity, authentication, and non-repudiation. The two main techniques are symmetric encryption, which uses a shared secret key, and asymmetric encryption, which uses public and private key pairs. Common symmetric algorithms discussed are AES, DES, and Blowfish, while asymmetric algorithms include RSA and Diffie-Hellman key exchange. The goal of cryptography is to provide security services like confidentiality, integrity, authentication, non-repudiation, availability, and access control.
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This document provides an overview of cryptography concepts including plain text, cipher text, encryption, decryption, and different cryptography techniques. It discusses substitution techniques like Caesar cipher and transposition techniques like columnar transposition. It also covers steganography, symmetric key cryptography including the DES algorithm, and asymmetric key cryptography with an introduction to digital signatures. Key topics covered include encryption algorithms, decryption processes, cryptanalysis, cryptology, and the working of techniques like Caesar cipher, columnar transposition, DES, and digital signatures at a high level.
Cryptography is the study of secure communication techniques. The document provides a high-level overview of basic cryptography concepts including its history, objectives, terminology, and types (symmetric, asymmetric, hash functions). Symmetric cryptography uses a single secret key for encryption and decryption while asymmetric cryptography uses two keys: a public key for encryption and a private key for decryption. Popular symmetric algorithms include AES and RSA. Hash functions like MD5 and SHA are used to verify message integrity. Quantum computing may improve applications like cancer treatment, traffic optimization, and weather forecasting by solving complex optimization problems.
Cryptography is the science of encrypting and decrypting data using mathematical concepts. It allows sensitive information to be stored or transmitted securely over insecure networks so that only the intended recipient can read it. The key concepts in cryptography include symmetric and asymmetric encryption algorithms, cryptosystems, cryptanalysis, cryptographic primitives like block ciphers and stream ciphers, and elements like keys, initialization vectors, and cryptographic services like confidentiality, integrity, authentication, and non-repudiation. Proper implementation with secure algorithms, large random keys, and protection of actual keys is important for cryptosystem strength.
This document provides an overview of symmetric encryption techniques, including:
- Symmetric encryption uses a shared secret key for both encryption and decryption.
- Classical encryption algorithms like the Caesar cipher and monoalphabetic substitution ciphers can be broken through frequency analysis.
- The Playfair cipher improved security over monoalphabetic ciphers by encrypting digrams, but it can still be broken with enough ciphertext.
- Polyalphabetic ciphers like the Vigenère cipher further increase security by using multiple cipher alphabets selected by a keyword.
A brief introduction to Crytography,the various types of crytography and the advantages and disadvantages associated to using the following tyes with some part of the RSA algorithm
Network security involves securing computer networks and systems. It is handled by network administrators who implement security policies, software, and hardware to protect networks from unauthorized access, misuse, or denial of resources. Network security aims to authenticate users, control access to resources, and ensure confidentiality, integrity, non-repudiation and availability of networks and resources. Common methods include authentication, access control, encryption, digital signatures, and monitoring systems for security audits.
This document provides an overview of cryptography concepts including:
- Cryptography is the study of encrypted information and involves encryption to convert plaintext to ciphertext and decryption to convert ciphertext back to plaintext.
- Ciphers use algorithms and keys to encrypt and decrypt messages, with symmetric encryption using the same key and asymmetric encryption using different keys.
- Common encryption methods include substitution ciphers that swap letters and transposition ciphers that rearrange letters.
- Cryptanalysis involves decrypting messages without the key by analyzing patterns and weaknesses in encryption algorithms.
Cryptography and network security Nit701Amit Pathak
Cryptography and network security descries the security parameter with the help of public and private key. Digital signature is one of the most important area which we apply in our daily life for transferring the data.
Symmetric Cipher Model,BruteForce attack, Cryptanalysis,Advantages of Symmetric cryptosystem,Model of conventional Encryption, model of conventional cryptosystem,Cryptography,Ciphertext,Plaintext,Decryption algorithm,Diadvantages of Symmetric Cryptosystem,Types of attacks on encrypted messages,Average time required for exhaustive key search
Cryptography : The Art of Secured MessagingSumit Satam
Cryptography is the art of securing messages by encrypting information into an unreadable cipher text format that can only be decrypted by those with the secret key. Modern cryptography techniques are virtually unbreakable. Cryptography is commonly used to protect email, credit cards, and corporate data on the internet. There are two main types of cryptography - symmetric which uses one shared key for encryption and decryption, and asymmetric which uses two mathematically related keys, a public and private key. Cryptography ensures confidentiality, integrity, and authenticity of messages.
The document discusses classical encryption techniques, including symmetric encryption which uses the same key for encryption and decryption. It describes ciphers like the Caesar cipher which substitutes letters by shifting the alphabet, the monoalphabetic cipher with one substitution table, and the polyalphabetic Vigenère cipher which uses multiple substitution alphabets. The document also covers the Playfair cipher which encrypts letters in pairs using a 5x5 keyword matrix, and discusses cryptanalysis techniques for breaking classical ciphers.
This document provides an overview of cryptography concepts including encryption, decryption, ciphers, block ciphers, stream ciphers, data encryption standards (DES), pseudo-random functions and permutations (PRFs and PRPs), integrity, key exchange, and public key encryption. Cryptography is the process of converting plain text to unintelligible ciphertext and vice versa. Encryption converts plain text to ciphertext while decryption converts ciphertext back to plain text. Ciphers and algorithms like DES are used to encrypt data using symmetric or asymmetric keys.
1. Encryption involves encoding information using an algorithm and cryptographic key to convert plain text into an encrypted cipher text that hides the information from anyone except the intended recipient. Symmetric encryption uses a single shared key for encryption and decryption while asymmetric encryption uses separate public and private keys.
2. Common encryption algorithms and standards discussed include AES, DES, RSA, MD5, and SHA which vary in their key sizes, block sizes, number of rounds, use of public/private keys, and applications for encrypting data and verifying message integrity.
3. Symmetric algorithms like AES and DES are block ciphers that encrypt fixed sized blocks of plain text while asymmetric algorithms like RSA use public/private key pairs
This document discusses cryptography and some of its key concepts. It defines cryptography as the science of secret writing and describes how it can be used to securely transmit messages and protect information. It then summarizes some common issues in cryptography like confidentiality, authentication, and integrity. It also defines important cryptography terms like plaintext, ciphertext, ciphers, keys, symmetric and asymmetric algorithms. Specific algorithms like DES, AES, RSA are also outlined at a high level.
This document provides an overview of cryptography concepts including plain text, cipher text, encryption, decryption, and different cryptography techniques. It discusses substitution techniques like Caesar cipher and transposition techniques like columnar transposition. It also covers steganography, symmetric key cryptography including the DES algorithm, and asymmetric key cryptography with an introduction to digital signatures. Key topics covered include encryption algorithms, decryption processes, cryptanalysis, cryptology, and the working of techniques like Caesar cipher, columnar transposition, DES, and digital signatures at a high level.
Cryptography is the study of secure communication techniques. The document provides a high-level overview of basic cryptography concepts including its history, objectives, terminology, and types (symmetric, asymmetric, hash functions). Symmetric cryptography uses a single secret key for encryption and decryption while asymmetric cryptography uses two keys: a public key for encryption and a private key for decryption. Popular symmetric algorithms include AES and RSA. Hash functions like MD5 and SHA are used to verify message integrity. Quantum computing may improve applications like cancer treatment, traffic optimization, and weather forecasting by solving complex optimization problems.
Cryptography is the science of encrypting and decrypting data using mathematical concepts. It allows sensitive information to be stored or transmitted securely over insecure networks so that only the intended recipient can read it. The key concepts in cryptography include symmetric and asymmetric encryption algorithms, cryptosystems, cryptanalysis, cryptographic primitives like block ciphers and stream ciphers, and elements like keys, initialization vectors, and cryptographic services like confidentiality, integrity, authentication, and non-repudiation. Proper implementation with secure algorithms, large random keys, and protection of actual keys is important for cryptosystem strength.
This document provides an overview of symmetric encryption techniques, including:
- Symmetric encryption uses a shared secret key for both encryption and decryption.
- Classical encryption algorithms like the Caesar cipher and monoalphabetic substitution ciphers can be broken through frequency analysis.
- The Playfair cipher improved security over monoalphabetic ciphers by encrypting digrams, but it can still be broken with enough ciphertext.
- Polyalphabetic ciphers like the Vigenère cipher further increase security by using multiple cipher alphabets selected by a keyword.
A brief introduction to Crytography,the various types of crytography and the advantages and disadvantages associated to using the following tyes with some part of the RSA algorithm
Network security involves securing computer networks and systems. It is handled by network administrators who implement security policies, software, and hardware to protect networks from unauthorized access, misuse, or denial of resources. Network security aims to authenticate users, control access to resources, and ensure confidentiality, integrity, non-repudiation and availability of networks and resources. Common methods include authentication, access control, encryption, digital signatures, and monitoring systems for security audits.
This document provides an overview of cryptography concepts including:
- Cryptography is the study of encrypted information and involves encryption to convert plaintext to ciphertext and decryption to convert ciphertext back to plaintext.
- Ciphers use algorithms and keys to encrypt and decrypt messages, with symmetric encryption using the same key and asymmetric encryption using different keys.
- Common encryption methods include substitution ciphers that swap letters and transposition ciphers that rearrange letters.
- Cryptanalysis involves decrypting messages without the key by analyzing patterns and weaknesses in encryption algorithms.
Cryptography and network security Nit701Amit Pathak
Cryptography and network security descries the security parameter with the help of public and private key. Digital signature is one of the most important area which we apply in our daily life for transferring the data.
Symmetric Cipher Model,BruteForce attack, Cryptanalysis,Advantages of Symmetric cryptosystem,Model of conventional Encryption, model of conventional cryptosystem,Cryptography,Ciphertext,Plaintext,Decryption algorithm,Diadvantages of Symmetric Cryptosystem,Types of attacks on encrypted messages,Average time required for exhaustive key search
Cryptography : The Art of Secured MessagingSumit Satam
Cryptography is the art of securing messages by encrypting information into an unreadable cipher text format that can only be decrypted by those with the secret key. Modern cryptography techniques are virtually unbreakable. Cryptography is commonly used to protect email, credit cards, and corporate data on the internet. There are two main types of cryptography - symmetric which uses one shared key for encryption and decryption, and asymmetric which uses two mathematically related keys, a public and private key. Cryptography ensures confidentiality, integrity, and authenticity of messages.
The document discusses classical encryption techniques, including symmetric encryption which uses the same key for encryption and decryption. It describes ciphers like the Caesar cipher which substitutes letters by shifting the alphabet, the monoalphabetic cipher with one substitution table, and the polyalphabetic Vigenère cipher which uses multiple substitution alphabets. The document also covers the Playfair cipher which encrypts letters in pairs using a 5x5 keyword matrix, and discusses cryptanalysis techniques for breaking classical ciphers.
This document provides an overview of cryptography concepts including encryption, decryption, ciphers, block ciphers, stream ciphers, data encryption standards (DES), pseudo-random functions and permutations (PRFs and PRPs), integrity, key exchange, and public key encryption. Cryptography is the process of converting plain text to unintelligible ciphertext and vice versa. Encryption converts plain text to ciphertext while decryption converts ciphertext back to plain text. Ciphers and algorithms like DES are used to encrypt data using symmetric or asymmetric keys.
1. Encryption involves encoding information using an algorithm and cryptographic key to convert plain text into an encrypted cipher text that hides the information from anyone except the intended recipient. Symmetric encryption uses a single shared key for encryption and decryption while asymmetric encryption uses separate public and private keys.
2. Common encryption algorithms and standards discussed include AES, DES, RSA, MD5, and SHA which vary in their key sizes, block sizes, number of rounds, use of public/private keys, and applications for encrypting data and verifying message integrity.
3. Symmetric algorithms like AES and DES are block ciphers that encrypt fixed sized blocks of plain text while asymmetric algorithms like RSA use public/private key pairs
This document discusses cryptography and some of its key concepts. It defines cryptography as the science of secret writing and describes how it can be used to securely transmit messages and protect information. It then summarizes some common issues in cryptography like confidentiality, authentication, and integrity. It also defines important cryptography terms like plaintext, ciphertext, ciphers, keys, symmetric and asymmetric algorithms. Specific algorithms like DES, AES, RSA are also outlined at a high level.
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
2. • Well established needs for secure communication
– War time communication
– Business transactions
– Illicit Love Affairs
• Requirements of secure communication
1. Secrecy
– Only intended receiver understands the message
2. Authentication
– Sender and receiver need to confirm each others identity
3. Message Integrity
– Ensure that their communication has not been altered, either
maliciously or by accident during transmission
Secure Communication
Needs and Requirements
3. • Cryptography is the science of secret, or hidden
writing
• It has two main Components:
1. Encryption
– Practice of hiding messages so that they can not be read by
anyone other than the intended recipient
2. Authentication & Integrity
– Ensuring that users of data/resources are the persons they claim
to be and that a message has not been surreptitiously altered
Cryptography
Basics
4. • Cipher is a method for encrypting messages
• Encryption algorithms are standardized & published
• The key which is an input to the algorithm is secret
– Key is a string of numbers or characters
– If same key is used for encryption & decryption the algorithm is called
symmetric
– If different keys are used for encryption & decryption the algorithm is called
asymmetric
Encryption
Cipher
Plain Text Encryption
Algorithm
Key A Key B
Cipher Text Plain Text
Decryption
Algorithm
5. • Algorithms in which the key for encryption and
decryption are the same are Symmetric
– Example: Caesar Cipher
• Types:
1. Block Ciphers
– Encrypt data one block at a time (typically 64 bits, or 128 bits)
– Used for a single message
2. Stream Ciphers
– Encrypt data one bit or one byte at a time
– Used if data is a constant stream of information
Encryption
Symmetric Algorithms
6. • Strength of algorithm is determined by the size of the key
– The longer the key the more difficult it is to crack
• Key length is expressed in bits
– Typical key sizes vary between 48 bits and 448 bits
• Set of possible keys for a cipher is called key space
– For 40-bit key there are 240 possible keys
– For 128-bit key there are 2128 possible keys
– Each additional bit added to the key length doubles the security
• To crack the key the hacker has to use brute-force
(i.e. try all the possible keys till a key that works is found)
– Super Computer can crack a 56-bit key in 24 hours
– It will take 272 times longer to crack a 128-bit key
(Longer than the age of the universe)
Symmetric Encryption
Key Strength
7. • Caesar Cipher is a method in which each letter in the alphabet
is rotated by three letters as shown
Substitution Ciphers
Caesar Cipher
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
D E F G H I J K L M N O P Q R S T U V W X Y Z A B C
• Let us try to encrypt the message
– Attack at Dawn
Assignment: Each student will exchange a secret message
with his/her closest neighbor about some other person in the
class and the neighbor will decipher it.
8. Substitution Ciphers
Caesar Cipher
Encryption
Plain Text
Message:
Attack at Dawn
Cipher Text
Message:
Dwwdfn Dw Gdyq
Cipher:
Caesar Cipher
Algorithm
Key (3)
Decryption
Plain Text
Message:
Attack at Dawn
Cipher Text
Message:
Dwwdfn Dw Gdyq
Cipher:
Caesar Cipher
Algorithm
Key (3)
How many different keys are possible?
9. • Any letter can be substituted for any other letter
– Each letter has to have a unique substitute
• There are 26! pairing of letters (~1026)
• Brute Force approach would be too time consuming
– Statistical Analysis would make it feasible to crack the key
Substitution Cipher
Monoalphabetic Cipher
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
M N B V C X Z A S D F G H J K L P O I U Y T R E W Q
Encrypted
Message:
Nkn, s gktc wky.
mgsbc
Message:
Bob, I love you.
Alice
Cipher:
Monoalphabetic
Cipher
Key
10. • Developed by Blaise de Vigenere
– Also called Vigenere cipher
• Uses a sequence of monoalpabetic ciphers in tandem
– e.g. C1, C2, C2, C1, C2
• Example
Substitution Cipher
Polyalphabetic Caesar Cipher
Encrypted
Message:
Gnu, n etox dhz.
tenvj
Message:
Bob, I love you.
Alice
Cipher:
Monoalphabetic
Cipher
Key
Plain Text 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
C1(k=6) F G H I J K L M N O P Q R S T U V W X Y Z A B C D E
C2(k=20) T U V W X Y Z A B C D E F G H I J K L M N O P Q R S
11. • Obtain a key to for the algorithm and then shift the alphabets
– For instance if the key is word we will shift all the letters by four and remove
the letters w, o, r, & d from the encryption
• We have to ensure that the mapping is one-to-one
– no single letter in plain text can map to two different letters in cipher text
– no single letter in cipher text can map to two different letters in plain text
Substitution Cipher
Using a key to shift alphabet
Encrypted
Message:
??
Message:
Bob, I love you.
Alice
Cipher:
WORD
Plain Text 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
C1(k=6) W O R D A B C E F G H I J K L M N P Q S T U V X Y Z
12. • This involves rearrangement of characters on the plain text into columns
• The following example shows how letters are transformed
– If the letters are not exact multiples of the transposition size there may be a
few short letters in the last column which can be padded with an infrequent
letter such as x or z
Transposition Cipher
Columnar Transposition
T H I S I
S A M E S
S A G E T
O S H O W
H O W A C
O L U M N
A R T R A
N S P O S
I T I O N
W O R K S
T S S O H
O A N I W
H A A S O
L R S T O
I M G H W
U T P I R
S E E O A
M R O O K
I S T W C
N A S N S
Plain Text Cipher Text
13. • The amount of secrecy needed should determine
the amount of labor appropriate for the encryption
and decryption.
• The set of keys and the enciphering algorithm
should be free from complexity.
• The implementation of the process should be as
simple as possible.
• Errors in ciphering should not propagate and cause
corruption of further information in the message.
• The size of the enciphered text should be no larger
than the text of the original message.
Ciphers
Shannon’s Characteristics of “Good” Ciphers
14. • It is based on sound mathematics.
– Good cryptographic algorithms are are derived from
solid principles.
• It has been analyzed by competent experts and
found to be sound.
– Since it is hard for the writer to envisage all possible
attacks on the algorithm
• It has stood the “test of time.”
– Over time people continue to review both mathematical
foundations of an algorithm and the way it builds upon
those foundations.
– The flaws in most algorithms are discovered soon after
their release.
Encryption Systems
Properties of Trustworthy Systems
15. • Cryptanalysis is the process of breaking an encryption code
– Tedious and difficult process
• Several techniques can be used to deduce the algorithm
– Attempt to recognize patterns in encrypted messages, to be able to
break subsequent ones by applying a straightforward decryption
algorithm
– Attempt to infer some meaning without even breaking the
encryption, such as noticing an unusual frequency of
communication or determining something by whether the
communication was short or long
– Attempt to deduce the key, in order to break subsequent messages
easily
– Attempt to find weaknesses in the implementation or environment
of use of encryption
– Attempt to find general weaknesses in an encryption algorithm,
without necessarily having intercepted any messages
Cryptanalysis
Techniques
16. • Goal of DES is to completely scramble the data and
key so that every bit of cipher text depends on every
bit of data and ever bit of key
• DES is a block Cipher Algorithm
– Encodes plaintext in 64 bit chunks
– One parity bit for each of the 8 bytes thus it reduces to
56 bits
• It is the most used algorithm
– Standard approved by US National Bureau of Standards
for Commercial and nonclassified US government use in
1993
Data Encryption Standard (DES)
Basics
17. • DES run in reverse to
decrypt
• Cracking DES
– 1997: 140 days
– 1999: 14 hours
• TripleDES uses DES 3
times in tandem
– Output from 1 DES is
input to next DES
Data Encryption Standard (DES)
Basics
64-bit input
L1 R1
F(L1, R1, K1)
L2 R2
L3 R3
L17 R17
56-bit key
48-bit k1
48-bit k2
48-bit k3
48-bit k16
F(L2, R2, K2)
F(L16, R16, K16)
18. Encryption Algorithm
Summary
Algorithm Type Key Size Features
DES Block
Cipher
56 bits Most Common, Not
strong enough
TripleDES Block
Cipher
168 bits
(112 effective)
Modification of DES,
Adequate Security
Blowfish Block
Cipher
Variable
(Up to 448 bits)
Excellent Security
AES Block
Cipher
Variable
(128, 192, or
256 bits)
Replacement for DES,
Excellent Security
RC4 Stream
Cipher
Variable
(40 or 128 bits)
Fast Stream Cipher,
Used in most SSL
implementations
19. • Any exposure to the secret key compromises secrecy
of ciphertext
• A key needs to be delivered to the recipient of the
coded message for it to be deciphered
– Potential for eavesdropping attack during transmission of
key
Symmetric Encryption
Limitations
20. • Uses a pair of keys for encryption
– Public key for encryption
– Private key for decryption
• Messages encoded using public key can only be decoded by
the private key
– Secret transmission of key for decryption is not required
– Every entity can generate a key pair and release its public key
Asymmetric Encryption
Basics
Plain Text
Cipher
Public Key Private Key
Cipher Text Plain Text
Cipher
21. • Two most popular algorithms are RSA & El Gamal
– RSA
• Developed by Ron Rivest, Adi Shamir, Len Adelman
• Both public and private key are interchangable
• Variable Key Size (512, 1024, or 2048 buts)
• Most popular public key algorithm
– El Gamal
• Developed by Taher ElGamal
• Variable key size (512 or 1024 bits)
• Less common than RSA, used in protocols like PGP
Asymmetric Encryption
Types
22. • Choose two large prime numbers p & q
• Compute n=pq and z=(p-1)(q-1)
• Choose number e, less than n, which has no common factor (other
than 1) with z
• Find number d, such that ed – 1 is exactly divisible by z
• Keys are generated using n, d, e
– Public key is (n,e)
– Private key is (n, d)
• Encryption: c = me mod n
– m is plain text
– c is cipher text
• Decryption: m = cd mod n
• Public key is shared and the private key is hidden
Asymmetric Encryption
RSA
23. • P=5 & q=7
• n=5*7=35 and z=(4)*(6) = 24
• e = 5
• d = 29 , (29x5 –1) is exactly divisible by 24
• Keys generated are
– Public key: (35,5)
– Private key is (35, 29)
• Encrypt the word love using (c = me mod n)
– Assume that the alphabets are between 1 & 26
Asymmetric Encryption
RSA
Plain Text Numeric Representation me Cipher Text (c = me mod n)
l 12 248832 17
o 15 759375 15
v 22 5153632 22
e 5 3125 10
24. • Decrypt the word love using (m = cd mod n)
– n = 35, c=29
Asymmetric Encryption
RSA
Cipher
Text
cd (m = me mod n) Plain
Text
17 481968572106750915091411825223072000 17 l
15 12783403948858939111232757568359400 15 o
22 852643319086537701956194499721110000000 22 v
10 100000000000000000000000000000 10 e
25. • Efficiency is lower than Symmetric Algorithms
– A 1024-bit asymmetric key is equivalent to 128-bit
symmetric key
• Potential for man-in-the middle attack
• It is problematic to get the key pair generated for the
encryption
Asymmetric Encryption
Weaknesses
26. • Hacker could generate a key pair, give the public key away and
tell everybody, that it belongs to somebody else. Now,
everyone believing it will use this key for encryption, resulting
in the hacker being able to read the messages. If he encrypts
the messages again with the public key of the real recipient, he
will not be recognized easily.
Asymmetric Encryption
Man-in-the-middle Attack
Bob
Attacker
David
Bob’s
Message
+ Public key
Cipher
David’s
Public Key
Trudeau
(Middle-man)
Trudeau’s
Message
+ public key
Cipher
Trudeau’s
Public Key
Bob’s
Encrypted
Message
Trudeau’s
Encrypted
Message
David’s
Message
+ public key
Cipher
Trudeau’s
Encrypted
Message
Bob’s
Public Key
Trudeau’s
New Message
+ public key
Cipher
Trudeau’s
Encrypted
Message
David’s
Public Key
27. • Used to improve efficiency
– Symmetric key is used for encrypting data
– Asymmetric key is used for encrypting the symmetric key
Asymmetric Encryption
Session-Key Encryption
Plain Text Cipher
(DES)
Session Key
Recipient’s Public Key
Cipher Text
Encrypted
Key
Cipher
(RSA)
Send to Recipient
28. • Pretty Good Privacy (PGP)
– Used to encrypt e-mail using session key encryption
– Combines RSA, TripleDES, and other algorithms
• Secure/Multipurpose Internet Mail Extension (S/MIME)
– Newer algorithm for securing e-mail
– Backed by Microsoft, RSA, AOL
• Secure Socket Layer(SSL) and Transport Layer Socket(TLS)
– Used for securing TCP/IP Traffic
– Mainly designed for web use
– Can be used for any kind of internet traffic
Asymmetric Encryption
Encryption Protocols
29. • Key agreement is a method to create secret key by exchanging only public
keys.
• Example
– Bob sends Alice his public key
– Alice sends Bob her public key
– Bob uses Alice’s public key and his private key to generate a session key
– Alice uses Bob’s public key and her private key to generate a session key
– Using a key agreement algorithm both will generate same key
– Bob and Alice do not need to transfer any key
Asymmetric Encryption
Key Agreement
Cipher
(DES)
Session Key
Cipher
(DES)
Bob’s
Public Key
Alice’s
Public Key
Bob’s
Private Key
Alice’s
Private Key
Alice and Bob
Generate Same
Session Key!
30. Asymmetric Encryption
Key Diffie-Hellman Mathematical Analysis
Bob & Alice
agree on non-secret
prime p and value a
Generate Secret
Random Number x
Compute Public Key
ax mod p
Compute Session Key
(ay)x mod p
Generate Secret
Random Number y
Compute Public Key
ay mod p
Compute Session Key
(ax)y mod p
Bob Alice
Identical Secret Key
Bob & Alice
exchange
public keys
31. • Diffie-Hellman is the first key agreement algorithm
– Invented by Whitfield Diffie & Martin Hellman
– Provided ability for messages to be exchanged securely
without having to have shared some secret information
previously
– Inception of public key cryptography which allowed keys
to be exchanged in the open
• No exchange of secret keys
– Man-in-the middle attack avoided
Asymmetric Encryption
Key Agreement con’t.
32. • Authentication is the process of validating the
identity of a user or the integrity of a piece of data.
• There are three technologies that provide
authentication
– Message Digests / Message Authentication Codes
– Digital Signatures
– Public Key Infrastructure
• There are two types of user authentication:
– Identity presented by a remote or application participating
in a session
– Sender’s identity is presented along with a message.
Authentication
Basics
33. • A message digest is a fingerprint for a document
• Purpose of the message digest is to provide proof that data
has not altered
• Process of generating a message digest from data is called
hashing
• Hash functions are one way functions with following
properties
– Infeasible to reverse the function
– Infeasible to construct two messages which hash to same digest
• Commonly used hash algorithms are
– MD5 – 128 bit hashing algorithm by Ron Rivest of RSA
– SHA & SHA-1 – 162 bit hashing algorithm developed by NIST
Authentication
Message Digests
Message
Message
Digest
Algorithm
Digest
34. • A message digest created with a key
• Creates security by requiring a secret key to be
possesses by both parties in order to retrieve the
message
Message Authentication Codes
Basics
Message
Message
Digest
Algorithm
Digest
Secret Key
35. • Password is secret character string only known to user and
server
• Message Digests commonly used for password authentication
• Stored hash of the password is a lesser risk
– Hacker can not reverse the hash except by brute force attack
• Problems with password based authentication
– Attacker learns password by social engineering
– Attacker cracks password by brute-force and/or guesswork
– Eavesdrops password if it is communicated unprotected over the
network
– Replays an encrypted password back to the authentication server
Password Authentication
Basics
36. • Set of rules that governs the communication of data related to authentication
between the server and the user
• Techniques used to build a protocol are
– Transformed password
• Password transformed using one way function before transmission
• Prevents eavesdropping but not replay
– Challenge-response
• Server sends a random value (challenge) to the client along with the authentication
request. This must be included in the response
• Protects against replay
– Time Stamp
• The authentication from the client to server must have time-stamp embedded
• Server checks if the time is reasonable
• Protects against replay
• Depends on synchronization of clocks on computers
– One-time password
• New password obtained by passing user-password through one-way function n times
which keeps incrementing
• Protects against replay as well as eavesdropping
Authentication Protocols
Basics
37. • Kerberos is an authentication service that uses symmetric key
encryption and a key distribution center.
• Kerberos Authentication server contains symmetric keys of all
users and also contains information on which user has access
privilege to which services on the network
Authentication Protocols
Kerberos
38. • Personal Tokens are hardware devices that generate unique
strings that are usually used in conjunction with passwords for
authentication
• Different types of tokens exist
– Storage Token: A secret value that is stored on a token and is available
after the token has been unlocked using a PIN
– Synchronous one-time password generator: Generate a new password
periodically (e.g. each minute) based on time and a secret code stored
in the token
– Challenge-response: Token computes a number based on a challenge
value sent by the server
– Digital Signature Token: Contains the digital signature private key and
computes a computes a digital signature on a supplied data value
• A variety of different physical forms of tokens exist
– e.g. hand-held devices, Smart Cards, PCMCIA cards, USB tokens
Authentication
Personal Tokens
39. • Uses certain biological characteristics for
authentication
– Biometric reader measures physiological indicia and
compares them to specified values
– It is not capable of securing information over the
network
• Different techniques exist
– Fingerprint Recognition
– Voice Recognition
– Handwriting Recognition
– Face Recognition
– Retinal Scan
– Hand Geometry Recognition
Authentication
Biometrics
40. • Probability of two irises producing exactly the same
code: 1 in 10 to the 78th power
• Independent variables (degrees of freedom)
extracted: 266
• IrisCode record size: 512 bytes
• Operating systems compatibility: DOS and
Windows (NT/95)
• Average identification speed (database of 100,000
IrisCode records): one to two seconds
Authentication
Iris Recognition
The scanning process takes advantage of the
natural patterns in people's irises, digitizing them
for identification purposes
Facts
41. • A digital signature is a data item which accompanies or is
logically associated with a digitally encoded message.
• It has two goals
– A guarantee of the source of the data
– Proof that the data has not been tampered with
Authentication
Digital Signatures
Message
Sent to
Receiver
Digest
Algorithm
Digital
Signature
Sent to
Receiver
Message
Digest
Sender’s
Private Key
Sender’s
Public Key
Message
Digest
Signature
Algorithm
Signature
Algorithm
Digest
Algorithm
Message
Digest
Sender Receiver
Same?
42. • A digital certificate is a signed statement by a trusted party that another
party’s public key belongs to them.
– This allows one certificate authority to be authorized by a different authority
(root CA)
• Top level certificate must be self signed
• Any one can start a certificate authority
– Name recognition is key to some one recognizing a certificate authority
– Verisign is industry standard certificate authority
Authentication
Digital Cerftificates
Identity
Information
Certificate
Authority’s
Private Key
Sender’s
Public Key
Signature
Algorithm
Certificate
43. • Chaining is the practice of signing a certificate with another private key
that has a certificate for its public key
– Similar to the passport having the seal of the government
• It is essentially a person’s public key & some identifying information signed
by an authority’s private key verifying the person’s identity
• The authorities public key can be used to decipher the certificate
• The trusted party is called the certificate authority
Authentication
Cerftificates Chaining
Certificate
Authority’s
Private Key
Signature
Algorithm
New Certificate
Certificate
44. • Practice of analyzing and breaking cryptography
• Resistance to crypt analysis is directly proportional to the key
size
– With each extra byte strength of key doubles
• Cracking Pseudo Random Number Generators
– A lot of the encryption algorithms use PRNGs to generate keys
which can also be cracked leading to cracking of algorithms
• Variety of methods for safe guarding keys (Key Management)
– Encryption & computer access protection
– Smart Cards
Cryptanalysis
Basics