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CRYPTO IN INFORMATION SECURITY
ELMIRA EBRAHIMI, NAZANIN BAYATI, MONA PORBIDEI, SHAGHAYEGH ARABNIA
TEACHER:MS.RAEISIAN
FALL2015
SHARIATY TECHNICAL COLLEGE
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INTRODUCTION
• Developing in computer network
• Secure data????
• Crypto via key
• The Roman Empire
• Most users, especially "encrypt information, Governments and military users
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INFORMATION SECURITY
• The protection of information and information systems from unauthorized
activities
• reach out, Disclosure, read, copy or record, manipulate, change, wreck.
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INFORMATION SECURITY
• Significant impact on the privacy of information security
• Fields can work:
• Securing networks and Infrastructure
• securing applications and data bases
• security testing
• auditing and information systems program review
• Planning the continuation of trade and reviews of electronic
crimes, etc.
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BASE CONCEPTS
• As the definition of information security, privacy, integrity
means and availability information from unauthorized
individuals
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• "Availability"
• "integrity“
• "Confidentiality"
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AVAILABILITY
• The information should be when needed
by authorized persons are available
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INTEGRITY
• Integrity means that the data will prevent unauthorized change
detection and change the information in the event of unauthorized
tampering
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CONFIDENTIALITY
• means that prevent information disclosure to unauthorized
•
•
•
individuals
In credit card, card number is encrypted
Privacy breach
Like s.o. look at your data or send your data by mobile
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ACCESS CONTROL
• To secure information
• Limited to authorized people
• Higher secure higher mechanism
• Mechanism use authorization
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AUTHORIZATION
• What u are?
• What u have?
• What u know?
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• Science of Encryption
• Encryption
• Decryption
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SCIENCE OF ENCRYPTION
• The science of codes and passwords
• Need to prove the identity of the sender and the recipient
• The message In the meantime
• Should not change the content of the message to make sure
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ENCRYPTION
• The operational
• initial data
• using an algorithm and a key
• becomes a non-understandable text
• no access to key, access to information from the encrypted text is impossible
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DECRYPTION
• A device or program
• that encrypted data returns to the first State
• The change of non-readable codes to text readable
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APPLICATIONS OF CRYPTOGRAPHY
• Credit card information
• The issue of membership in the forums
• Private information
• Details of the personal information
• Sensitive information in an organization
• Information relating to bank accounts
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CRYPTO
• Cryptography  making “secret codes”
• Cryptanalysis  breaking “secret codes”
• Crypto  all of the above (and more)
Definitions of cryptography
(plaintext)
(Ciphertext)
(key)
ALGORITHMS
• Basic assumption
• The system is completely known to the attacker
• Only the key is secret
• That is, crypto algorithms are not secret
• This is known as Kerckhoffs’ Principle
• Why do we make this assumption?
History
SIMPLE SUBSTITUTION
• Plaintext HELLO GUYS
• Key:
Plaintext
ab c d e f g h i j k l mn o p q r s t u v w x y z
Ciphertext
D E F G H I J K L MN O P Q R S T U VWX Y Z A B C
 Ciphertext:
Khoor Jxbv
 Shift by 3
CAESAR’S CIPHER
http://enigma.louisedade.co.uk/howitworks.html
DOUBLE TRANSPOSITION
One-time Pad: Encryption
e=000 h=001 i=010 k=011 l=100 r=101 s=110 t=111
TAXONOMY OF CRYPTOGRAPHY
• Symmetric Key
•
•
Same key for encryption and decryption
Two types: Stream ciphers _ like a one-time pad, Block ciphers
• Public Key (or asymmetric crypto)
•
Two keys, one for encryption (public), and one for decryption
(private)
•
Also, digital signatures  nothing comparable in symmetric
key crypto
• Hash algorithms
•
Sometimes viewed as “one way” crypto
SYMMETRIC KEY CRYPTO
STREAM CIPHERS
• Once upon a time, the king of crypto
• Today, not as popular as block ciphers
• A5/1
• Based on shift registers
• Used in GSM mobile phone system
A5/1
X
x0
x1
x2 x3 x4
x5
x6
x7
x8
x9
x10
x11
x12 x13 x14 x15 x16 x17 x18

Y
y0
y1
y2
y3
y4
y5
y6
y7
y8
y9 y10 y11 y12 y13 y14 y15 y16 y17 y18 y19 y20 y21

Z
z0
z1
z2
z3
z4
z5
z6
z7
z8
z9
z10 z11 z12 z13 z14 z15 z16 z17 z18 z19 z20 z21 z22

maj(x8, y10, z10)

BLOCK CIPHERS
• Plaintext and ciphertext consist of fixed-sized blocks
• Ciphertext obtained from plaintext by iterating a round
function
• Input to round function consists of key and the output of
previous round
• Usually implemented in software
• Data Encryption Standard(DES)
• Advanced Encryption Standard(AES)
PUBLIC KEY CRYPTOGRAPHY
• Two keys
• Sender uses recipient’s public key to encrypt
• Recipient uses private key to decrypt
• Based on “trap door one way function”
• RSA is the gold standard in public key crypto
HASH FUNCTION
• Crypto hash function h(x) must provide
• Compression output length is small
• Efficiency h(x) easy to compute for any x
• One-way given a value y it is infeasible to find an x
such that h(x) = y
VISUAL CRYPTOGRAPHY
If a pixel is white, randomly choose a or b for Alice’s/Bob’s
shares
 If
a pixel is black,
randomly choose c
or d
 no info from one
share
•
‫منابع‬
http://wikipedia.org/wiki/(computer_security)
www.irannetbook.com
Wikipedia
hit.mums.ac.ir
www.sarzaminDownload.com
www.certcc.ir
Question ??
THANKS FOR LISTENING