cryptography chapter1
TRANSCRIPT
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CryptographyUnit 1
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Introduction
The art of war teaches us to rely not on the likelihood of the enot coming, but on our own readiness to receive him; not onchance of his not attacking, but rather on the fact that we hour position unassailable.
The Art of War, Sun Tzu
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Introduction
Hidden writing
Increasingly used to protect information
Can ensure confidentiality
Integrity and Authenticity too
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What is Cryptography?
Cryptography is the science of using mathematics to encrypdecrypt data.
cryptanalysis is the science of analyzing and breaking secure
communication.
Cryptology embraces both cryptography and cryptanalysis
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How does it work?
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Outline History
Terms & Definitions
Symmetric and Asymmetric Algorithms
Hashing
PKI Concepts
Attacks on Cryptosystems
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History The Manual Era
Dates back to at least 2000 B.C.
Pen and Paper Cryptography
Examples
Scytale
Atbash
Caesar
Vigenre
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Encryption Technology in Ancient
India Jaimini was one of the disciples of Veda Vyasa. He
put a compendium of Sutras and is called asJaimini Sutras.
He has put it cryptically the houses he was
referring to in his slokas
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Ka Ta Pa Ya di Sutra
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For eg. The sutra:
Dara Bhagya
Shoolasyaargala
Nidhyayathu
From the table
Da=8 ra=2, reverse an
divide by 12 gives thehouse in question
28 (mod 12) = 4
Similarly for Bhagya=4
14 mod 12 = 2
Shoola = 5 la = 3
35 mod 12 = 11
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Encryption Technology in Ancient
India gopi bhagya madhuvrata
srngiso dadhi sandhiga
khala jivita khatava
gala hala rasandarago = 3, pi = 1, bha =4 , ya = 1 , ma = 5 , duv = 9
31415926535897932384626433832792
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History The Mechanical Era
Invention of cipher machines
Examples
Confederate Armys Cipher Disk
Japanese Red and Purple Machines German Enigma
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Speak Like a Crypto GeekPlaintext A message in its natural format readable by a
attacker
Ciphertext Message altered to be unreadable by anyonexcept the intended recipients
Key Sequence that controls the operation and behavio
the cryptographic algorithm
Keyspace Total number of possible values of keys in acrypto algorithm
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Speak Like a Crypto Geek (2)Initialization Vector Random values used with ciphers
ensure no patterns are created during encryption
Cryptosystem The combination of algorithm, key, and k
management functions used to perform cryptographicoperations
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Cryptosystem Services
Confidentiality
Integrity
Authenticity
Nonrepudiation
Access Control
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Types of Cryptography Stream-based Ciphers
One at a time, please
Mixes plaintext with key stream
Good for real-time services
Block Ciphers
Amusement Park Ride
Substitution and transposition
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Encryption Systems
Substitution Cipher Convert one letter to another
Cryptoquip
Transposition Cipher Change position of letter in text
Word Jumble
Monoalphabetic Cipher Caesar
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Encryption Systems
Polyalphabetic Cipher Vigenre
Modular Mathematics
Running Key Cipher One-time Pads
Randomly generated keys
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What Technique did Jason Use?
Jason works in the sales and marketing department for a very large advertising agency located in Atlanta. Jason is work
important marketing campaign for his company's largest client. Before the project could be completed and implementeadvertising company comes out with the exact same marketing materials and advertising, thus rendering all the work dclient unusable. Jason is questioned about this and says he has no idea how all the material ended up in the hands of a c
Without any proof, Jason's company cannot do anything except move on. After working on another high profile client fothe marketing and sales material again ends up in the hands of another competitor and is released to the public before can finish the project. Once again, Jason says that he had nothing to do with it and does not know how this could have given leave with pay until they can figure out what is going on.
Jason's supervisor decides to go through his email and finds a number of emails that were sent to the competitors that
marketing material. The only items in the emails were attached jpg files, but nothing else. Jason's supervisor opens the cannot find anything out of the ordinary with them. What technique has Jason most likely used?
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Steganography
Hiding a message within another medium, such as animage
No key is required
Example Modify color map of JPEG image
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Cryptosystem Services
Confidentiality
Integrity
Authenticity
Nonrepudiation
Access Control
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Security Services
X.800 defines it as: a service provided by a protocol layer ofcommunicating open systems, which ensures adequate securitsystems or of data transfers
RFC 2828 defines it as: a processing or communication servicprovided by a system to give a specific kind of protection to resources
X.800 defines it in 5 major categories
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Security Mechanisms (X.800)
specific security mechanisms: encipherment, digital signatures, access controls, data integrity, auth
exchange, traffic padding, routing control, notarization
pervasive security mechanisms: trusted functionality, security labels, event detection, security audit
security recovery
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Continued
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Figure 1.2 Taxonomy of attacks with relation to security goals
1.2.1 Attacks Threatening Confidentiality
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Snoopingrefers to unauthorized access to or interceptio
data.
Traffic analysis refers to obtaining some other typ
information by monitoring online traffic.
1.2.2 Attacks Threatening Integrity
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Modificationmeans that the attacker intercepts the mes
and changes it.
Masquerading or spoofing happens when the atta
impersonates somebody else.
Replaying means the attacker obtains a
of a message sent by a user and later tries to replay it.
Repudiationmeans that sender of the message might
deny that she has sent the message; the receiver of
message might later deny that he has received the messa
1.2.3 Attacks Threatening Availability
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Denial of service(DoS) is a very common attack. It
slow down or totally interrupt the service of a system.
1.2.4 Passive Versus Active Attacks
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Table 1.1 Categorization of passive and active attacks
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Security services
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Security mechanisms
SecurityM
echanisms
Encipherment
Data Integrity
Digital Signature
Authentication
exchange
Traffic Padding
Routing Control
Notarization
Access Control
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Classify Security Attacks
passive attacks - eavesdropping on, or monitoring of, transm obtain message contents, or monitor traffic flows
active attacks modification of data stream to: masquerade of one entity as some other replay previous messages modify messages in transit
denial of service
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Relation between SecurityService and Mechanism
Security Service Security Mechanism
Data confidentiality Encipherment and routing control
Data Integrity Encipherment, digital signature, data
integrity
Authentication Encipherment, digital signature,
authentication exchangesNonrepudiation Digital signature, data integrity, and
notarization
Access Control Access control mechanism
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Types of Attacks
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